Gravity’s New Dawn: The Quest for a Unified Theory

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Kind: captions
Language: en

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This is Spacetime Series 28, episode 65


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for broadcast on the 30th of May,


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2025. Coming up on Spacetime, a new


00:00:09.120 --> 00:00:11.110
theory of gravity which brings the long


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sought after theory of everything closer


00:00:13.200 --> 00:00:16.150
to reality. Is there a hot side to the


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moon? And astronomers discover white


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dwarf pulsars for the first time. All


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that and more coming up on Spaceime.


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Welcome to Spaceime with Stuart Garry.


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[Music]




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Scientists have developed a new theory


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of gravity which brings the long sought


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after theory of everything just a little


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bit closer to reality. A quantum theory


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of gravity would clear the path to


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answering some of the biggest questions


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in physics. The study detailed in the


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journal reports on progress in physics


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claims a unified theory combining


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gravity with the other fundamental


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forces of nature that's electromagnetism


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and the strong and weak nuclear forces


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may well at long last be within reach.


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Bringing gravity into the fold has been


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the goal of generations of physicists


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who have struggled to reconcile the


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incompatibility of the two cornerstones


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of modern physics, namely quantum field


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theory and Albert Einstein's theory of


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general relativity. The key has been


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developing a new quantum theory of


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gravity which describes gravity in ways


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compatible with the standard model of


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particle physics, the cornerstone of our


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understanding of the universe. And in


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the process, it's opening the door to an


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improved understanding of how the


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universe began. While the world of


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theoretical physics may seem remote from


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applicable technology, the findings are


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remarkable. See, modern technology is


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built on fundamental advances. For


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example, the GPS in your smartphone


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works thanks to Albert Einstein's theory


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of gravity. The study's authors Miko


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Partanan and Julie both from Alto


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University say that within a few years a


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new hypothesis may well unlock crucial


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understanding. Now if it does turn out


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to lead to a complete quantum field


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theory of gravity then eventually it'll


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give answers to the very difficult


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problems of understanding singularities


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the center of black holes and even


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understanding the big bang of creation


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itself. However, we're not there yet.


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Some fundamental questions of physics


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still remain under this so-called theory


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of everything. For example, current


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theories still can't explain why there's


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more matter than anti-atter in the


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observable universe. And they still


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don't know what dark energy and what


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dark matter really are. The key to this


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new hypothesis was finding a way to


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describe gravity in a suitable gauge


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theory. A kind of theory in which


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particles interact with each other


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through a field. Now, the most familiar


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gauge field is the electromagnetic


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field. Ki says that when electrically


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charged particles interact with each


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other, they interact through the


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electromagnetic field which is the


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permanent gauge field. So when particles


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have energy, the interactions they have


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just because they have energy would


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happen through the gravitational field.


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But a challenge long facing physicists


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is finding a gauge theory for gravity.


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One that's compatible with the gauge


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theories of the other three fundamental


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forces. The electromagnetic force, the


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weak nuclear force, and the strong


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nuclear force. The standard model of


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particle physics is itself a gauge


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theory which describes those three


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forces and has certain symmetries. The


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tenant says the main idea is to have a


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gravity gauge theory with a symmetry


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that's similar to the standard model


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symmetries. Instead of basing the theory


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on the very different kind of space-time


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symmetry involved in Einstein's general


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relativity. Without such a hypothesis,


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physicists couldn't reconcile our two


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most powerful theories, quantum field


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theory and general relativity. Quantum


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field theory describes the world of the


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very small, tiny particles interacting


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in probabilistic ways. On the other


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hand, general relativity describes the


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grand physics of the cosmic world, the


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universe as a whole. So, they're both


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descriptions of our universe, but from


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very different perspectives. And both


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theories have been confirmed with


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extraordinary precision, yet they're


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still incompatible with each other. And


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because gravitational interactions are


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weak, more precision's needed in order


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to study true quantum gravity effects


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beyond general relativity. Tanninsan


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says a quantum theory of gravity is


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needed in order to understand what kind


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of phenomena there are in cases where


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there's a gravitational field with high


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energies. The sort of conditions you'd


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find around black holes and very early


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in the universe's existence just after


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the big bang. And they're the sort of


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places where existing theories of


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physics all stop working. Although the


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hypothesis is promising, the authors


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point out they've not yet completed its


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proof. It uses a technical procedure


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known as renormalization. That's a


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mathematical way of dealing with the


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infinities that show up in the


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calculations. Now, so far the authors


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have shown that while this works up to a


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certain point for so-called first order


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terms, they yet to make sure that these


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infinities can be eliminated throughout


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the entire calculation. You see, if


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reormalization doesn't work for higher


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order terms, you'll get infinite


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results. So it's vital to show that this


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renormalization continues to work and


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therefore they still need to make a


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complete proof. Nevertheless, it's


00:05:19.280 --> 00:05:23.350
fascinating work. This spaceime still to


00:05:23.360 --> 00:05:25.990
come. Is there a hot side to the moon?


00:05:26.000 --> 00:05:28.070
And astronomers discover their first


00:05:28.080 --> 00:05:30.550
white dwarf pulsars. All that and more


00:05:30.560 --> 00:05:33.160
still to come on Spaceime.


00:05:33.170 --> 00:05:35.510
[Music]


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spacetime. And now it's back to our


00:07:44.250 --> 00:07:48.029
[Music]


00:07:48.039 --> 00:07:51.029
show. A new study claims the moon's near


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earth-facing side is actually hotter


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than its far side. The findings are


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reported in the journal nature based on


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data from NASA's Grail spacecraft and


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the twin eb and flow spacecraft which


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have been studying the moon from orbit.


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Our moon is gravitationally tidly locked


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to the earth. That means the same side


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always faces our planet. Even more


00:08:10.800 --> 00:08:13.189
fascinating is the dichotomy of the moon


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which has long intrigued scientists. You


00:08:15.759 --> 00:08:17.749
see there are notable differences in


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geology, volcanism and custal thickness


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between the lunar near and far sides.


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The moon's near side appears darker and


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it's dominated by smooth ancient lava


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flows indicating a high concentration of


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volcanism. On the other hand, the far


00:08:32.159 --> 00:08:34.630
side is far more rugged. The new study


00:08:34.640 --> 00:08:36.790
using data from Grail suggests that this


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dichotomy is caused by 2 to 3%


00:08:39.200 --> 00:08:41.029
difference in the lunar mantle's ability


00:08:41.039 --> 00:08:43.750
to deform on each side. The author


00:08:43.760 --> 00:08:45.750
suggested the reason is that the moon's


00:08:45.760 --> 00:08:49.350
near side mantle is up to 170° C hotter


00:08:49.360 --> 00:08:51.509
than its far side. It's thought this


00:08:51.519 --> 00:08:52.870
thermal difference could be caused by


00:08:52.880 --> 00:08:54.710
the radioactive decay of thorium and


00:08:54.720 --> 00:08:56.790
titanium within the moon's near side,


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which could be a remnant of the volcanic


00:08:58.480 --> 00:09:00.070
activity that formed the near side


00:09:00.080 --> 00:09:02.150
surface between 3 and 4 billion years


00:09:02.160 --> 00:09:04.550
ago. The authors say the same methods,


00:09:04.560 --> 00:09:06.230
which have now being used to study the


00:09:06.240 --> 00:09:08.150
moon's interior from orbit, could also


00:09:08.160 --> 00:09:09.670
be used to measure differences in the


00:09:09.680 --> 00:09:11.350
structure of other planetary bodies,


00:09:11.360 --> 00:09:13.190
such as the red planet Mars, the


00:09:13.200 --> 00:09:15.750
Saturnian moon Enceladus, and the Jovian


00:09:15.760 --> 00:09:19.590
moon Ganymede. This is spacetime. Still


00:09:19.600 --> 00:09:21.590
to come, astronomers discover a white


00:09:21.600 --> 00:09:24.070
dwarf star acting like a pulsar and the


00:09:24.080 --> 00:09:26.269
June solstice, the constellation


00:09:26.279 --> 00:09:28.630
Sagittarius, and the torids meteor


00:09:28.640 --> 00:09:30.389
shower are among the highlights of the


00:09:30.399 --> 00:09:34.940
June night skies on Skywatch.


00:09:34.950 --> 00:09:47.110
[Music]


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A white dwarf and a red dwarf have been


00:09:49.360 --> 00:09:50.949
discovered closely orbiting each other


00:09:50.959 --> 00:09:54.150
and emitting radio pulses every 2 hours.


00:09:54.160 --> 00:09:56.070
Findings reported in the journal Nature


00:09:56.080 --> 00:09:58.470
Astronomy mean that neutron stars are no


00:09:58.480 --> 00:10:00.710
longer the only stellar bodies that emit


00:10:00.720 --> 00:10:03.590
such pulses. Now, a key factor in this


00:10:03.600 --> 00:10:05.670
discovery could be the way the binary


00:10:05.680 --> 00:10:07.910
pair is spaced unusually far apart from


00:10:07.920 --> 00:10:09.670
each other. Thanks to follow-up


00:10:09.680 --> 00:10:11.430
observations using optical and X-ray


00:10:11.440 --> 00:10:13.110
telescopes, the study's authors were


00:10:13.120 --> 00:10:14.550
able to determine the origin of these


00:10:14.560 --> 00:10:16.790
pulsars coming from this binary system


00:10:16.800 --> 00:10:18.949
with certainty. The findings are


00:10:18.959 --> 00:10:20.150
important because they're hoping to


00:10:20.160 --> 00:10:21.670
explain the sources of these strange


00:10:21.680 --> 00:10:23.509
radio emissions which are found right


00:10:23.519 --> 00:10:27.150
across the Milky Way galaxy. This is


00:10:27.160 --> 00:10:42.350
[Music]


00:10:42.360 --> 00:10:44.790
spaceime. And time now to check out the


00:10:44.800 --> 00:10:46.590
night skies of June on


00:10:46.600 --> 00:10:49.030
Skywatch. June is the fourth month of


00:10:49.040 --> 00:10:50.870
the old Roman calendar. and it's named


00:10:50.880 --> 00:10:53.110
after Juno who was the wife of Jupiter


00:10:53.120 --> 00:10:54.630
is also the equivalent to the Greek


00:10:54.640 --> 00:10:57.110
goddess Hera. Another belief is that the


00:10:57.120 --> 00:10:58.710
month's name actually comes from the


00:10:58.720 --> 00:11:01.069
Latin word juniors which means younger


00:11:01.079 --> 00:11:03.670
ones. It's a great time to look up the


00:11:03.680 --> 00:11:05.990
night skies and marvel at the majesty of


00:11:06.000 --> 00:11:07.990
the Milky Way as it puts on its


00:11:08.000 --> 00:11:11.110
spectacular overhead display. June also


00:11:11.120 --> 00:11:12.630
marks the winter solstice in the


00:11:12.640 --> 00:11:14.310
Southern Hemisphere, which this year


00:11:14.320 --> 00:11:16.710
happens at 12:42 in the afternoon of


00:11:16.720 --> 00:11:18.710
Saturday, June the 21st, Australian


00:11:18.720 --> 00:11:21.670
Eastern Standard Time. That's 10:42 in


00:11:21.680 --> 00:11:23.829
the evening of Friday, June the 20th, US


00:11:23.839 --> 00:11:26.310
Eastern Daylight Time, and 2:42 in the


00:11:26.320 --> 00:11:28.150
morning of Saturday, June the 21st,


00:11:28.160 --> 00:11:30.550
Greenwich Meime. And while it means the


00:11:30.560 --> 00:11:32.630
start of winter south of the equator, it


00:11:32.640 --> 00:11:34.310
means the arrival of summer for our


00:11:34.320 --> 00:11:35.990
lucky listeners in the northern part of


00:11:36.000 --> 00:11:38.470
the planet. The June solstice occurs


00:11:38.480 --> 00:11:40.470
when the sun reaches its most northerly


00:11:40.480 --> 00:11:42.630
point in the sky as seen from Earth.


00:11:42.640 --> 00:11:44.550
Zenith appearing to be directly above


00:11:44.560 --> 00:11:47.190
the Tropic of Cancer. See, Earth's


00:11:47.200 --> 00:11:49.110
seasons are governed by the tilt of the


00:11:49.120 --> 00:11:51.269
planet's axis as it journeys around the


00:11:51.279 --> 00:11:53.430
Sun. Now, the Earth's axis is always


00:11:53.440 --> 00:11:55.350
pointed the same direction in space


00:11:55.360 --> 00:11:57.110
regardless of the position of the planet


00:11:57.120 --> 00:11:59.829
Earth as it orbits around the Sun. So on


00:11:59.839 --> 00:12:01.670
the day of the June solstice, Earth's


00:12:01.680 --> 00:12:04.630
south pole is tilted by 23 1/2° away


00:12:04.640 --> 00:12:06.629
from the sun, while the north pole is


00:12:06.639 --> 00:12:08.470
tilted by the same amount towards the


00:12:08.480 --> 00:12:11.190
sun. The sun rising in the northeast and


00:12:11.200 --> 00:12:13.590
setting in the northwest. Of course, 6


00:12:13.600 --> 00:12:15.190
months later, when the south pole is


00:12:15.200 --> 00:12:16.710
tilted towards the sun, it's the


00:12:16.720 --> 00:12:18.710
southern hemisphere summer. And in


00:12:18.720 --> 00:12:20.990
between, we have the autumn and spring


00:12:21.000 --> 00:12:23.750
equinoxes. Temperatures on Earth aren't


00:12:23.760 --> 00:12:25.269
determined by Earth's orbital distance


00:12:25.279 --> 00:12:27.190
from the Sun, but rather the angle of


00:12:27.200 --> 00:12:29.829
the Sun's rays striking the Earth. So,


00:12:29.839 --> 00:12:32.069
in summer, the sun's high in the sky and


00:12:32.079 --> 00:12:33.910
the rays hit the planet at a steep


00:12:33.920 --> 00:12:36.389
angle. In winter, the sun's lower in the


00:12:36.399 --> 00:12:38.310
sky and the rays strike the Earth at a


00:12:38.320 --> 00:12:40.790
far shallower angle. Now, in most parts


00:12:40.800 --> 00:12:43.030
of the world, the seasons begin on the


00:12:43.040 --> 00:12:45.670
day of the solstice or equinox. However,


00:12:45.680 --> 00:12:48.230
Australia is weird. Here, seasons begin


00:12:48.240 --> 00:12:50.230
on the first day of a specific calendar


00:12:50.240 --> 00:12:52.150
month. That means the 1st of March for


00:12:52.160 --> 00:12:54.150
autumn, the 1st of June for winter, the


00:12:54.160 --> 00:12:56.069
1st of September for spring, and you


00:12:56.079 --> 00:12:58.190
guessed it, the 1st of December for


00:12:58.200 --> 00:13:01.670
summer. Okay, let's check out the stars.


00:13:01.680 --> 00:13:03.430
Well, almost overhead this time of the


00:13:03.440 --> 00:13:06.389
year, we find the constellation Virgo.


00:13:06.399 --> 00:13:08.389
Virgo is named after the goddess of


00:13:08.399 --> 00:13:10.310
justice and the harvest in ancient Greek


00:13:10.320 --> 00:13:12.389
mythology, who used her scales to weigh


00:13:12.399 --> 00:13:14.629
good and evil. However, she became so


00:13:14.639 --> 00:13:16.470
disenchanted with the evil deeds of men,


00:13:16.480 --> 00:13:18.310
she wound up throwing away her scales


00:13:18.320 --> 00:13:20.629
and retreated to the heavens.


00:13:20.639 --> 00:13:22.310
Interestingly, the ancient Egyptians


00:13:22.320 --> 00:13:24.870
also associate Virgo with agriculture.


00:13:24.880 --> 00:13:26.870
There she was the goddess Isis who


00:13:26.880 --> 00:13:28.629
sprinkled the heads of wheat across the


00:13:28.639 --> 00:13:31.750
sky forming the Milky Way. To science,


00:13:31.760 --> 00:13:33.829
Virgo is a tightly packed region


00:13:33.839 --> 00:13:36.230
containing some 2,000 galaxies, all


00:13:36.240 --> 00:13:38.150
gravitationally bound into a giant


00:13:38.160 --> 00:13:40.470
galaxy cluster some 60 million light


00:13:40.480 --> 00:13:43.190
years away. In fact, our own local group


00:13:43.200 --> 00:13:45.350
of galaxies dominated by the Milky Way


00:13:45.360 --> 00:13:47.430
and Andromeda are outlying members of


00:13:47.440 --> 00:13:50.389
this group. The Virgo cluster is at the


00:13:50.399 --> 00:13:52.069
heart of what's known as the Virgo


00:13:52.079 --> 00:13:54.790
supercluster, a massive galactic node in


00:13:54.800 --> 00:13:56.550
the large scale cosmic web-like


00:13:56.560 --> 00:13:58.790
structure of the universe. The mass of


00:13:58.800 --> 00:14:00.949
the Virgo supercluster is so great that


00:14:00.959 --> 00:14:03.350
its gravity generates the Virgo centric


00:14:03.360 --> 00:14:05.350
flow, causing our Milky Way galaxy as


00:14:05.360 --> 00:14:06.870
well as Andromeda and all the other


00:14:06.880 --> 00:14:08.550
members of the local galactic group to


00:14:08.560 --> 00:14:10.629
move towards the supercluster at around


00:14:10.639 --> 00:14:11.629
400


00:14:11.639 --> 00:14:14.150
km/s. That's despite the accelerating


00:14:14.160 --> 00:14:16.069
expansion of the universe over cosmic


00:14:16.079 --> 00:14:18.710
time scales. The Virgo supercluster is


00:14:18.720 --> 00:14:20.790
now thought to be a lobe on an even


00:14:20.800 --> 00:14:22.629
larger galactic supercluster called


00:14:22.639 --> 00:14:25.269
Lania, the center of which is known as


00:14:25.279 --> 00:14:27.990
the Great Attractor. Despite the Virgo


00:14:28.000 --> 00:14:30.470
cluster size, it's so far away from us,


00:14:30.480 --> 00:14:31.990
it's hard to see without a decently


00:14:32.000 --> 00:14:33.910
sized backyard telescope. You'll need


00:14:33.920 --> 00:14:35.509
something at least 100 millimeters in


00:14:35.519 --> 00:14:38.389
diameter or larger in order to see it.


00:14:38.399 --> 00:14:40.310
Now, if you look directly straight up at


00:14:40.320 --> 00:14:42.310
Zenith, you'll see the constellation


00:14:42.320 --> 00:14:45.110
Corvis the Crow. Greek mythology tells


00:14:45.120 --> 00:14:47.350
us that Corvvis could talk to humans,


00:14:47.360 --> 00:14:50.230
but he was a lazy bird and so Apollo


00:14:50.240 --> 00:14:52.150
took away his ability to speak and


00:14:52.160 --> 00:14:53.550
banished into the


00:14:53.560 --> 00:14:55.829
heavens. One of the most spectacular


00:14:55.839 --> 00:14:57.910
highlights of the constellations Virgo


00:14:57.920 --> 00:15:00.710
and Corvvis is the spectacular sombrero


00:15:00.720 --> 00:15:02.870
galaxy M104.


00:15:02.880 --> 00:15:04.629
Visible with a good pair of binoculars


00:15:04.639 --> 00:15:06.470
or a small backyard telescope, this


00:15:06.480 --> 00:15:08.389
stunning spiral galaxy is seen almost


00:15:08.399 --> 00:15:10.470
edge on and it will provide you with a


00:15:10.480 --> 00:15:12.710
spectacular backlit view of its galactic


00:15:12.720 --> 00:15:14.790
bold stars and the molecular gas and


00:15:14.800 --> 00:15:18.870
dust lanes in its arms. M104 is located


00:15:18.880 --> 00:15:21.269
some 31 million lighty years away and


00:15:21.279 --> 00:15:23.189
it's moving away from the Milky Way at


00:15:23.199 --> 00:15:24.670
about 1,000


00:15:24.680 --> 00:15:27.430
km/s. A light year is about 10 trillion


00:15:27.440 --> 00:15:29.990
km. The distance a photon can travel in


00:15:30.000 --> 00:15:31.750
a year at the speed of light, which is


00:15:31.760 --> 00:15:34.389
about 300,000 kilometers/s in a vacuum


00:15:34.399 --> 00:15:36.189
and the ultimate speed limit of the


00:15:36.199 --> 00:15:38.790
universe. The sombrero galaxy has a


00:15:38.800 --> 00:15:41.269
diameter of around 50,000 light years,


00:15:41.279 --> 00:15:43.430
making it about 30% the size of our


00:15:43.440 --> 00:15:46.230
Milky Way galaxy. It's surrounded up to


00:15:46.240 --> 00:15:48.790
2,000 globular clusters and it has an


00:15:48.800 --> 00:15:50.790
active central super massive black hole


00:15:50.800 --> 00:15:52.790
at least a billion times the mass of our


00:15:52.800 --> 00:15:55.990
sun. Now, by comparison, Sagittarius A


00:15:56.000 --> 00:15:57.430
star, that's the super massive black


00:15:57.440 --> 00:15:59.189
hole at the center of our own galaxy,


00:15:59.199 --> 00:16:01.430
has just 4.3 million times the sun's


00:16:01.440 --> 00:16:04.069
mass. Globular clusters are either the


00:16:04.079 --> 00:16:06.069
central remnants of smaller galaxies


00:16:06.079 --> 00:16:07.990
cannibalized by larger ones, or


00:16:08.000 --> 00:16:10.069
alternatively, they're tight balls


00:16:10.079 --> 00:16:12.470
comprising millions of stars, which all


00:16:12.480 --> 00:16:14.310
originally formed at the same time in


00:16:14.320 --> 00:16:16.069
the same collapsing molecular gas and


00:16:16.079 --> 00:16:18.389
dust cloud. By the way, the brightest


00:16:18.399 --> 00:16:20.949
star in Virgo is Spyer, a spectroscopic


00:16:20.959 --> 00:16:23.389
binary located some 250 lighty years


00:16:23.399 --> 00:16:26.310
away. Spectroscopic binaries are stars


00:16:26.320 --> 00:16:28.150
that are orbiting so close together they


00:16:28.160 --> 00:16:29.910
can only be told apart by their


00:16:29.920 --> 00:16:31.949
individual spectrographic


00:16:31.959 --> 00:16:34.550
signatures. Now, looking about 20° above


00:16:34.560 --> 00:16:36.470
the western horizon early in the evening


00:16:36.480 --> 00:16:37.910
this time of the year, you'll find the


00:16:37.920 --> 00:16:40.230
fourth brightest object in the sky, the


00:16:40.240 --> 00:16:43.269
dog star Sirius. Only the sun, the moon,


00:16:43.279 --> 00:16:45.910
and the planet Venus look brighter.


00:16:45.920 --> 00:16:47.990
Looking to the northwest or right of


00:16:48.000 --> 00:16:49.910
Sirius, you'll find another fairly


00:16:49.920 --> 00:16:52.470
bright star, Proion, the brightest star


00:16:52.480 --> 00:16:55.350
in Canthis Minor, the lesser dog. In


00:16:55.360 --> 00:16:57.670
Greek mythology, Canis Major and Canis


00:16:57.680 --> 00:17:00.870
Minor were Orion's hunting dogs. Proon


00:17:00.880 --> 00:17:03.990
is a binary star system. It comprises a


00:17:04.000 --> 00:17:06.069
spectral type F main sequence white


00:17:06.079 --> 00:17:08.470
yellow star, Pron A, and a faint white


00:17:08.480 --> 00:17:11.829
dwarf companion, Proion B. Main sequence


00:17:11.839 --> 00:17:13.750
stars are those undergoing hydrogen


00:17:13.760 --> 00:17:16.390
fusion into helium in their cores.


00:17:16.400 --> 00:17:18.630
Astronomers describe stars in terms of


00:17:18.640 --> 00:17:20.789
spectral types, a classification system


00:17:20.799 --> 00:17:22.350
based on temperature and


00:17:22.360 --> 00:17:24.230
characteristics. The hottest, most


00:17:24.240 --> 00:17:26.150
massive, and most luminous stars, and


00:17:26.160 --> 00:17:29.029
then spectrotype O blue stars. They're


00:17:29.039 --> 00:17:31.029
followed by spectrotype B blue white


00:17:31.039 --> 00:17:34.230
stars. Then spectrotype A white stars,


00:17:34.240 --> 00:17:36.710
spectrotype F, whitish yellow stars,


00:17:36.720 --> 00:17:38.710
spectrotype G yellow stars. That's where


00:17:38.720 --> 00:17:41.029
our sun fits in. Then there spectral


00:17:41.039 --> 00:17:43.350
type K orange stars and the coolest and


00:17:43.360 --> 00:17:45.430
least massive known stars are spectral


00:17:45.440 --> 00:17:48.150
type M red stars. Now each spectral


00:17:48.160 --> 00:17:50.150
classification can also be subdivided


00:17:50.160 --> 00:17:52.150
using a numeric digit to represent


00:17:52.160 --> 00:17:53.990
temperature with zero being the hottest


00:17:54.000 --> 00:17:56.390
and nine the coolest. And then you can


00:17:56.400 --> 00:17:58.590
add a Roman numeral to represent


00:17:58.600 --> 00:18:00.789
luminosity. Put all that together and


00:18:00.799 --> 00:18:03.029
our sun is officially classified as a


00:18:03.039 --> 00:18:07.430
G2V or G25 yellow dwarf star. Now also


00:18:07.440 --> 00:18:09.270
included in the stellar classification


00:18:09.280 --> 00:18:12.470
system are spectrotypes LT and Y which


00:18:12.480 --> 00:18:14.230
are assigned to failed stars known as


00:18:14.240 --> 00:18:16.390
brown dwarves. Some of which were born


00:18:16.400 --> 00:18:18.549
as spectrotype M red stars but became


00:18:18.559 --> 00:18:20.590
brown dwarves after losing some of their


00:18:20.600 --> 00:18:23.190
mass. Brown dwarves fit into a unique


00:18:23.200 --> 00:18:24.950
category between the largest planets


00:18:24.960 --> 00:18:26.710
which can be up to 13 times the mass of


00:18:26.720 --> 00:18:28.870
say Jupiter and the smallest spectrotype


00:18:28.880 --> 00:18:31.750
M red dwarf stars which are around 75 to


00:18:31.760 --> 00:18:33.909
80 times the mass of Jupiter or around


00:18:33.919 --> 00:18:36.950
0.08 08 solar masses. Now, the other


00:18:36.960 --> 00:18:38.390
type of star we just mentioned were


00:18:38.400 --> 00:18:40.789
white dwarves. They're the stellar


00:18:40.799 --> 00:18:43.590
corpses of sunlike stars. Having used up


00:18:43.600 --> 00:18:45.430
all its nuclear fuel supply, fusing


00:18:45.440 --> 00:18:47.990
hydrogen into helium, these stars expand


00:18:48.000 --> 00:18:50.549
into red giants as they fuse helium into


00:18:50.559 --> 00:18:53.350
carbon and oxygen. The sun and stars


00:18:53.360 --> 00:18:55.510
like it aren't massive enough to fuse


00:18:55.520 --> 00:18:58.150
carbon and oxygen into heavier elements,


00:18:58.160 --> 00:19:00.789
so they turn off. Eventually, the outer


00:19:00.799 --> 00:19:02.549
gazes envelopes will float off into


00:19:02.559 --> 00:19:04.630
space as spectacular objects known as


00:19:04.640 --> 00:19:07.430
planetary nebula. What's left behind is


00:19:07.440 --> 00:19:09.909
a super dense white hot stellar core


00:19:09.919 --> 00:19:12.310
about the size of the Earth. This is the


00:19:12.320 --> 00:19:14.870
white dwarf, which will slowly cool over


00:19:14.880 --> 00:19:18.789
the Aons. The white dwarf Pro B is about


00:19:18.799 --> 00:19:21.590
0.6 times the mass of the sun and has a


00:19:21.600 --> 00:19:24.950
diameter of around 8,600 kilometers.


00:19:24.960 --> 00:19:27.270
Located about 11.6 six light years away.


00:19:27.280 --> 00:19:29.029
Proon A is about one and a half times


00:19:29.039 --> 00:19:31.029
the mass and twice the radius of our


00:19:31.039 --> 00:19:33.510
sun. But it also has some seven times


00:19:33.520 --> 00:19:35.510
the sun's luminosity. That makes it


00:19:35.520 --> 00:19:37.510
unusually bright for a star of this


00:19:37.520 --> 00:19:39.750
type. And that suggests that it's now


00:19:39.760 --> 00:19:41.190
starting to evolve off the main


00:19:41.200 --> 00:19:43.590
sequence, having fused nearly all of its


00:19:43.600 --> 00:19:46.470
core hydrogen into helium. So that means


00:19:46.480 --> 00:19:48.789
it's slowly expanding out to become a


00:19:48.799 --> 00:19:51.190
subgiant as it begins fusing its core


00:19:51.200 --> 00:19:53.270
helium into oxygen and carbon and


00:19:53.280 --> 00:19:55.230
burning hydrogen further out from the


00:19:55.240 --> 00:19:57.990
core. As it continues to expand, the


00:19:58.000 --> 00:20:00.070
star will eventually swirl somewhere


00:20:00.080 --> 00:20:02.470
between 80 and 150 times its current


00:20:02.480 --> 00:20:04.470
diameter in the process becoming a red


00:20:04.480 --> 00:20:06.870
or orange giant. This will probably


00:20:06.880 --> 00:20:09.230
happen within the next 10 to 100 million


00:20:09.240 --> 00:20:12.710
years. The two stars Proon A and B orbit


00:20:12.720 --> 00:20:15.110
each other every 40.82 82 Earth years at


00:20:15.120 --> 00:20:17.110
an average distance of 15 astronomical


00:20:17.120 --> 00:20:19.350
units, about the distance Uranus is from


00:20:19.360 --> 00:20:21.909
the Sun. An astronomical unit is the


00:20:21.919 --> 00:20:23.510
average distance between the Earth and


00:20:23.520 --> 00:20:25.590
the Sun, which is around 150 million


00:20:25.600 --> 00:20:29.190
kilometers or 8.3 light minutes. Now,


00:20:29.200 --> 00:20:31.190
looking towards the northnorthwest right


00:20:31.200 --> 00:20:32.789
now, and you'll see the constellation


00:20:32.799 --> 00:20:34.789
Leo the Lion looking like a bunch of


00:20:34.799 --> 00:20:36.789
stars shaped like an upside down


00:20:36.799 --> 00:20:40.710
question mark. Located just 36.7 lighty


00:20:40.720 --> 00:20:43.510
years away, Octurus is a bloated aging


00:20:43.520 --> 00:20:46.549
red giant about 7.1 billion years old


00:20:46.559 --> 00:20:49.430
and nearing the end of its life. Having


00:20:49.440 --> 00:20:51.590
used up all its core hydrogen, it's now


00:20:51.600 --> 00:20:54.630
fusing helium into carbon and oxygen.


00:20:54.640 --> 00:20:56.390
This has caused the star, which is only


00:20:56.400 --> 00:20:58.310
slightly more massive than our sun, to


00:20:58.320 --> 00:21:00.789
expand out to around 25 times the sun's


00:21:00.799 --> 00:21:03.190
diameter. In the process, becoming about


00:21:03.200 --> 00:21:06.390
170 times as luminous. It will soon puff


00:21:06.400 --> 00:21:08.390
off its outer gaseous envelope as a


00:21:08.400 --> 00:21:10.310
planetary nebula, revealing its white


00:21:10.320 --> 00:21:12.549
hot stellar core. Now, in Greek


00:21:12.559 --> 00:21:15.110
mythology, Acturus was the guardian of


00:21:15.120 --> 00:21:17.430
the bear. Now, this is a reference to it


00:21:17.440 --> 00:21:19.190
being next to the constellations Ursa


00:21:19.200 --> 00:21:21.110
Major and Ursa Minor, the greater and


00:21:21.120 --> 00:21:23.270
lesser bears. Now, there's some


00:21:23.280 --> 00:21:25.190
indications that Arcturus could have a


00:21:25.200 --> 00:21:27.029
binary stellar companion, but the


00:21:27.039 --> 00:21:29.270
results remain inconclusive. There's


00:21:29.280 --> 00:21:31.110
also some speculation that it could have


00:21:31.120 --> 00:21:33.190
a large planet or substellar object


00:21:33.200 --> 00:21:35.750
around 12 Jupiter masses orbiting it.


00:21:35.760 --> 00:21:37.750
That's close to brown dwarf size, but


00:21:37.760 --> 00:21:40.190
again, the search remains


00:21:40.200 --> 00:21:42.630
inconclusive. Now, to the east are the


00:21:42.640 --> 00:21:43.990
three brightest stars in the


00:21:44.000 --> 00:21:45.750
constellation Libra, the scales of


00:21:45.760 --> 00:21:47.909
justice. They're visible about halfway,


00:21:47.919 --> 00:21:50.789
about 40° above the horizon. These


00:21:50.799 --> 00:21:52.789
represent the claws of Scorpius, the


00:21:52.799 --> 00:21:54.789
scorpion, which is chasing a ry across


00:21:54.799 --> 00:21:57.110
the sky. The brightest star in the


00:21:57.120 --> 00:21:59.590
constellation Scorpius is Alpha Scorpia


00:21:59.600 --> 00:22:03.029
or Antares, the Scorpion's heart. Easily


00:22:03.039 --> 00:22:05.190
seen with the unaded eye, this red super


00:22:05.200 --> 00:22:07.990
giant some 550 light years away. And


00:22:08.000 --> 00:22:09.590
it's one of the largest known stars in


00:22:09.600 --> 00:22:12.230
the universe. It has about 18 times the


00:22:12.240 --> 00:22:15.110
mass and 883 times the diameter of our


00:22:15.120 --> 00:22:17.669
sun. And it has some 10,000 times more


00:22:17.679 --> 00:22:20.950
luminosity than our sun. Now looking to


00:22:20.960 --> 00:22:22.630
the southeast now and you'll see the


00:22:22.640 --> 00:22:25.430
constellation Sagittarius, the archer.


00:22:25.440 --> 00:22:27.350
Sagittarius marks the direction of the


00:22:27.360 --> 00:22:29.830
center of our galaxy, the Milky Way.


00:22:29.840 --> 00:22:32.070
It's located 26,000 lighty years away


00:22:32.080 --> 00:22:33.830
and is home to the galaxy's super


00:22:33.840 --> 00:22:37.029
massive black hole, Sagittarius a star.


00:22:37.039 --> 00:22:39.510
To the ancient Babylonians, Sagittarius


00:22:39.520 --> 00:22:41.669
was the god Nurgal, the centaur, a


00:22:41.679 --> 00:22:43.270
creature that was half man and half


00:22:43.280 --> 00:22:45.830
horse. By the time Greek mythology took


00:22:45.840 --> 00:22:48.070
over, Sagittarius was carrying his bow


00:22:48.080 --> 00:22:49.830
loaded with an arrow pointing towards


00:22:49.840 --> 00:22:52.190
Antares, the heart of Scorpius, the


00:22:52.200 --> 00:22:54.470
Scorpion. The center of the Milky Way


00:22:54.480 --> 00:22:56.230
galaxy, and its super massive black


00:22:56.240 --> 00:22:58.549
hole, Sagittarius A star, lie in the


00:22:58.559 --> 00:23:00.990
westernmost part of the constellation


00:23:01.000 --> 00:23:02.870
Sagittarius. One of the brightest stars


00:23:02.880 --> 00:23:05.350
in Sagittarius is Alpha Sagittaria or


00:23:05.360 --> 00:23:07.590
Rockbat, meaning the arch's knee. A


00:23:07.600 --> 00:23:11.270
spectral type B blue star located 182


00:23:11.280 --> 00:23:12.870
lighty years away. It is some two and a


00:23:12.880 --> 00:23:14.549
half times the diameter of the sun and


00:23:14.559 --> 00:23:17.110
it's about 40 times as luminous.


00:23:17.120 --> 00:23:18.870
Astronomers think it's surrounded by a


00:23:18.880 --> 00:23:20.710
dense debris disc and a newborn


00:23:20.720 --> 00:23:22.470
companion star which is only just


00:23:22.480 --> 00:23:24.789
joining the main sequence. Now the


00:23:24.799 --> 00:23:27.070
overall brightest star in Sagittarius or


00:23:27.080 --> 00:23:29.110
Calstralus, the southern part of the


00:23:29.120 --> 00:23:31.990
bow. Epsilon Sagittarius is a binary


00:23:32.000 --> 00:23:34.470
star system located 143 light years


00:23:34.480 --> 00:23:36.870
away. The primary star is an evolved


00:23:36.880 --> 00:23:39.029
spectrotype E blue giant now at the end


00:23:39.039 --> 00:23:41.669
of its life on the main sequence. It has


00:23:41.679 --> 00:23:43.430
about three and a half times the sun's


00:23:43.440 --> 00:23:45.830
mass, almost 7 times its radius, and


00:23:45.840 --> 00:23:48.870
it's radiating around 363 times the


00:23:48.880 --> 00:23:51.590
sun's luminosity. It's also a very


00:23:51.600 --> 00:23:53.750
strong X-ray source, and it's spinning


00:23:53.760 --> 00:23:55.510
incredibly rapidly with an estimated


00:23:55.520 --> 00:23:58.750
radial velocity of some 236


00:23:58.760 --> 00:24:01.669
km/s. The system also displays an excess


00:24:01.679 --> 00:24:03.590
of infrared radiation emissions,


00:24:03.600 --> 00:24:04.870
suggesting the presence of a


00:24:04.880 --> 00:24:07.750
circumstellar disc of dust. The second


00:24:07.760 --> 00:24:09.909
star in the system appears to be inside


00:24:09.919 --> 00:24:12.390
this debris disc. Now, astronomers are


00:24:12.400 --> 00:24:14.070
speculating that this may well develop


00:24:14.080 --> 00:24:16.549
into a spectral type G yellow dwarf star


00:24:16.559 --> 00:24:20.230
with about 95% of our sun's mass. Sigma


00:24:20.240 --> 00:24:21.830
Sagittarius or Nunki is the


00:24:21.840 --> 00:24:24.070
constellation's second brightest star.


00:24:24.080 --> 00:24:26.390
We know the name Ni has Babylonian


00:24:26.400 --> 00:24:28.590
origins. However, its meaning remains a


00:24:28.600 --> 00:24:30.870
mystery. It's thought to represent the


00:24:30.880 --> 00:24:32.950
ancient Babylonian city of Erdo on the


00:24:32.960 --> 00:24:35.430
Euphrates River. If correct, that would


00:24:35.440 --> 00:24:37.830
make NI the oldest known star name


00:24:37.840 --> 00:24:40.789
currently in use. It's a spectrotype B


00:24:40.799 --> 00:24:43.590
blue star located about 260 lighty years


00:24:43.600 --> 00:24:45.990
away. It has about 8 times the sun's


00:24:46.000 --> 00:24:47.909
mass, about 4 and a half times its


00:24:47.919 --> 00:24:50.549
radius, and some 3,300 times the


00:24:50.559 --> 00:24:53.350
luminosity of our sun. Zeta Sagittaria,


00:24:53.360 --> 00:24:55.430
or a cell at the armpit, is a binary


00:24:55.440 --> 00:24:57.430
star system 88 lighty years away from


00:24:57.440 --> 00:24:59.750
the sun. It's currently speeding away


00:24:59.760 --> 00:25:01.750
from the solar system, but may once have


00:25:01.760 --> 00:25:03.269
been as near as 1 and a half lightyears


00:25:03.279 --> 00:25:05.190
from the sun about 1.4 million years


00:25:05.200 --> 00:25:07.269
ago, and that would make it a former


00:25:07.279 --> 00:25:09.590
close neighbor. One of the stars in the


00:25:09.600 --> 00:25:11.990
system is a spectrotype a white giant,


00:25:12.000 --> 00:25:13.990
while the other is a spectrotype a white


00:25:14.000 --> 00:25:15.830
super giant. The pair orbiting each


00:25:15.840 --> 00:25:18.789
other every 21 Earth years. The systems


00:25:18.799 --> 00:25:21.669
combined mass is thought to be 5.26


00:25:21.679 --> 00:25:24.070
times the mass of our sun. Delta


00:25:24.080 --> 00:25:26.149
Sagittary appears to be a double star


00:25:26.159 --> 00:25:28.630
system located around 348 lighty years


00:25:28.640 --> 00:25:31.909
away and listed as an orange giant. Then


00:25:31.919 --> 00:25:33.909
there's EA Sagittary, another double


00:25:33.919 --> 00:25:36.549
star system. This one located 146 lighty


00:25:36.559 --> 00:25:38.630
years from Earth. The primary star in


00:25:38.640 --> 00:25:41.350
the system is an aging bloated red giant


00:25:41.360 --> 00:25:43.990
on the astopic giant branch. That means


00:25:44.000 --> 00:25:46.070
it's no longer fusing hydrogen or helium


00:25:46.080 --> 00:25:47.909
at its core and is instead fusing


00:25:47.919 --> 00:25:50.149
heavier elements, burning hydrogen and


00:25:50.159 --> 00:25:52.230
helium in the shell. It's already


00:25:52.240 --> 00:25:54.870
expanded out to some 57 times the radius


00:25:54.880 --> 00:25:57.029
of our sun and is now nearing the end of


00:25:57.039 --> 00:25:59.590
its life. The second star in the system


00:25:59.600 --> 00:26:01.909
is a spectrotype F main sequence white


00:26:01.919 --> 00:26:03.750
yellow dwarf which appears to be in a


00:26:03.760 --> 00:26:05.430
binary system with a primary star


00:26:05.440 --> 00:26:08.950
orbiting it every 1,270 Earth years.


00:26:08.960 --> 00:26:11.350
High Sagittary or a Balder is a triple


00:26:11.360 --> 00:26:13.830
star system located 510 light years


00:26:13.840 --> 00:26:16.149
away. The primary star in the system


00:26:16.159 --> 00:26:18.470
appears to be a spectrotype F white


00:26:18.480 --> 00:26:20.470
yellow giant which has exhausted its


00:26:20.480 --> 00:26:22.470
core hydrogen and so is now off the main


00:26:22.480 --> 00:26:25.430
sequence and evolving into a red giant.


00:26:25.440 --> 00:26:27.669
We know pi Sagittary has two nearby


00:26:27.679 --> 00:26:29.669
companions but little is known about


00:26:29.679 --> 00:26:32.390
either of them. Beta Sagittaria or Arab


00:26:32.400 --> 00:26:34.230
the Achilles tendon is the designation


00:26:34.240 --> 00:26:36.710
shed by two separate star systems. One's


00:26:36.720 --> 00:26:39.190
about 378 light years from Earth, the


00:26:39.200 --> 00:26:41.990
other 139 light years away. Beta


00:26:42.000 --> 00:26:44.149
Sagittary A is a spectrotype B blue


00:26:44.159 --> 00:26:46.710
dwarf star while Beta Sagittary B is a


00:26:46.720 --> 00:26:49.510
white yellow giant. Lying nearly at the


00:26:49.520 --> 00:26:50.950
very center of the constellation


00:26:50.960 --> 00:26:53.750
Sagittarius is Nova Sagittary which was


00:26:53.760 --> 00:26:56.549
only discovered in 2015 and as its name


00:26:56.559 --> 00:26:59.110
suggests is Anova, a white dwarf in a


00:26:59.120 --> 00:27:01.029
binary system with another star which is


00:27:01.039 --> 00:27:02.789
constantly drawing material off its


00:27:02.799 --> 00:27:05.190
companion. Now, once enough material


00:27:05.200 --> 00:27:07.029
reaches the surface of the white dwarf,


00:27:07.039 --> 00:27:09.350
this added mass triggers a thermonuclear


00:27:09.360 --> 00:27:11.269
explosion, causing the star to suddenly


00:27:11.279 --> 00:27:13.510
light up like a beacon and then slowly


00:27:13.520 --> 00:27:15.830
begin fading again over the following


00:27:15.840 --> 00:27:18.310
weeks and months. Now, this blast isn't


00:27:18.320 --> 00:27:19.669
strong enough to destroy the white


00:27:19.679 --> 00:27:21.430
dwarf, only the additional material that


00:27:21.440 --> 00:27:23.830
it's picked up. And with this additional


00:27:23.840 --> 00:27:25.909
material now burnt off, the same cycle


00:27:25.919 --> 00:27:27.990
can start over again. And the process


00:27:28.000 --> 00:27:30.070
can repeat itself on time scales ranging


00:27:30.080 --> 00:27:31.750
from every few years to tens of


00:27:31.760 --> 00:27:33.990
thousands of years apart.


00:27:34.000 --> 00:27:36.549
The Sagittarius constellation also hosts


00:27:36.559 --> 00:27:39.029
many star clusters and nebula, including


00:27:39.039 --> 00:27:40.470
some of the best known astronomical


00:27:40.480 --> 00:27:43.350
objects in the sky. These include the


00:27:43.360 --> 00:27:46.149
Lagoon Nebula, Messier 8, a spectacular


00:27:46.159 --> 00:27:48.149
pink emission nebula located 8,000


00:27:48.159 --> 00:27:50.390
lighty years away, which measures 140


00:27:50.400 --> 00:27:53.029
lighty years by 60 light years across.


00:27:53.039 --> 00:27:55.190
The central area of the Lagoon Nebula is


00:27:55.200 --> 00:27:57.110
also known as the Hourglass Nebula


00:27:57.120 --> 00:27:59.269
because of its distinctive shape. The


00:27:59.279 --> 00:28:01.430
shapes caused by matter propelled by a


00:28:01.440 --> 00:28:03.190
massive star forming in a region known


00:28:03.200 --> 00:28:05.510
as Hershel 36, one of the few star


00:28:05.520 --> 00:28:07.190
forming nebula that's possible to see


00:28:07.200 --> 00:28:09.830
with the unaded eye. The Lagoon Nebula


00:28:09.840 --> 00:28:11.430
was instrumental in the discovery of


00:28:11.440 --> 00:28:13.590
what are known as Boach globules, more


00:28:13.600 --> 00:28:15.750
than 17,000 of which have now been found


00:28:15.760 --> 00:28:18.389
in the nebula. Astronomers believe Bach


00:28:18.399 --> 00:28:21.029
globules contain embriionic protoars


00:28:21.039 --> 00:28:22.870
destined to eventually become new


00:28:22.880 --> 00:28:25.190
stellar generations.


00:28:25.200 --> 00:28:26.870
Probably the best known nebula in


00:28:26.880 --> 00:28:29.909
Sagittarius is Messier 17, the Horsehead


00:28:29.919 --> 00:28:33.590
Nebula. It's located 4,890 lighty years


00:28:33.600 --> 00:28:35.909
away and is a dense region of ionized


00:28:35.919 --> 00:28:39.110
atomic hydrogen. Also known as the Omega


00:28:39.120 --> 00:28:41.669
or Swan Nebula, it spans some 15 lighty


00:28:41.679 --> 00:28:43.909
years in diameter and has some 800 times


00:28:43.919 --> 00:28:46.549
the mass of our sun. It's considered one


00:28:46.559 --> 00:28:48.389
of the brightest and most massive star


00:28:48.399 --> 00:28:50.470
forming regions in our galaxy with a


00:28:50.480 --> 00:28:51.990
geometry very similar to the Orion


00:28:52.000 --> 00:28:54.149
Nebula except that it's viewed air on


00:28:54.159 --> 00:28:56.470
rather than face on. The open star


00:28:56.480 --> 00:28:57.870
cluster


00:28:57.880 --> 00:29:00.870
NGC618 is embedded within the nebulosity


00:29:00.880 --> 00:29:02.870
and it causes the gases of the nebula to


00:29:02.880 --> 00:29:04.870
shine due to intense radiation from


00:29:04.880 --> 00:29:07.590
these hot young stars. Open star


00:29:07.600 --> 00:29:09.510
clusters are loosely bound groups of a


00:29:09.520 --> 00:29:11.350
few thousand stars which were originally


00:29:11.360 --> 00:29:13.269
all formed in the same molecular gas and


00:29:13.279 --> 00:29:15.510
dust cloud but are not as tightly bonded


00:29:15.520 --> 00:29:17.470
together as the stars in globular


00:29:17.480 --> 00:29:19.750
clusters. It's thought open clusters


00:29:19.760 --> 00:29:21.430
generally survive for a few hundred


00:29:21.440 --> 00:29:23.430
million years with the most massive ones


00:29:23.440 --> 00:29:25.990
surviving for maybe a few billion years.


00:29:26.000 --> 00:29:27.909
In contrast, the more massive globular


00:29:27.919 --> 00:29:29.830
clusters exert far stronger


00:29:29.840 --> 00:29:31.269
gravitational attraction to their


00:29:31.279 --> 00:29:33.190
members and they therefore can survive


00:29:33.200 --> 00:29:36.070
much longer in cosmic time. The nebula


00:29:36.080 --> 00:29:38.470
is thought to contain over 800 stars,


00:29:38.480 --> 00:29:39.909
including more than a hundred of the


00:29:39.919 --> 00:29:42.149
largest, most massive spectrotype OMB


00:29:42.159 --> 00:29:44.950
blue stars. More than a thousand


00:29:44.960 --> 00:29:47.190
additional stars are now being formed in


00:29:47.200 --> 00:29:49.029
the surrounding molecular gas and dust


00:29:49.039 --> 00:29:51.190
clouds. It's also one of the youngest


00:29:51.200 --> 00:29:53.029
known clusters in the galaxy with an age


00:29:53.039 --> 00:29:55.510
of just a million years. The cloud of


00:29:55.520 --> 00:29:57.590
interstellar material forming the nebula


00:29:57.600 --> 00:29:59.750
is roughly 40 light years in diameter


00:29:59.760 --> 00:30:01.990
and it's thought to contain some 30,000


00:30:02.000 --> 00:30:03.909
solar masses.


00:30:03.919 --> 00:30:05.909
Another famous nebulosity is the


00:30:05.919 --> 00:30:09.029
Trifford Nebula Messia 20. It's another


00:30:09.039 --> 00:30:10.950
large star forming emission nebula


00:30:10.960 --> 00:30:13.990
containing many very young hot stars


00:30:14.000 --> 00:30:15.830
located somewhere between 2,000 and


00:30:15.840 --> 00:30:17.430
9,000 lighty years from Earth. The


00:30:17.440 --> 00:30:19.029
Triffford Nebula has a diameter of


00:30:19.039 --> 00:30:21.669
around 50 lighty years. Now, the outside


00:30:21.679 --> 00:30:23.590
of the Trefford Nebula is a bluish


00:30:23.600 --> 00:30:25.029
reflection nebula, while the inner


00:30:25.039 --> 00:30:27.350
region is glowing pink thanks to ionized


00:30:27.360 --> 00:30:29.830
hydrogen. There are two dark bands


00:30:29.840 --> 00:30:31.750
dividing the Triffford Nebula into three


00:30:31.760 --> 00:30:34.710
regions or loes. Hydrogen in the nebula


00:30:34.720 --> 00:30:36.710
is being ionized by a central triple


00:30:36.720 --> 00:30:38.549
star system which formed in the


00:30:38.559 --> 00:30:40.710
intersection of the two bands creating


00:30:40.720 --> 00:30:43.590
the characteristic pink color. Other


00:30:43.600 --> 00:30:46.029
star forming regions such as


00:30:46.039 --> 00:30:48.549
NGC559 which is located 5,000 lighty


00:30:48.559 --> 00:30:50.149
years from Earth contain both red


00:30:50.159 --> 00:30:53.269
emission and blue reflection regions.


00:30:53.279 --> 00:30:55.430
This grouping of the Lagoon Nebula, the


00:30:55.440 --> 00:30:57.389
Triffid Nebula, and


00:30:57.399 --> 00:31:00.669
NGC6559 is known as the Sagittarius


00:31:00.679 --> 00:31:03.190
triplet. Another spectacular site in


00:31:03.200 --> 00:31:07.230
Sagittarius is the Red Spider Nebula,


00:31:07.240 --> 00:31:09.750
NGC6537. It's a planetary nebula some


00:31:09.760 --> 00:31:12.389
8,000 lighty years from Earth. It is a


00:31:12.399 --> 00:31:14.789
prominent two-lo shape. Now, this could


00:31:14.799 --> 00:31:16.710
be due to a binary companion or possibly


00:31:16.720 --> 00:31:18.710
magnetic fields and has an S-shaped


00:31:18.720 --> 00:31:20.230
symmetry with the loes opposite each


00:31:20.240 --> 00:31:22.630
other appearing similar. The central


00:31:22.640 --> 00:31:25.110
white dwarf remnant to the original star


00:31:25.120 --> 00:31:27.830
produces a powerful 10,000 degree hot


00:31:27.840 --> 00:31:31.190
3,000 km/s stellar wind. And that wind


00:31:31.200 --> 00:31:33.990
is generating 100 billion km high waves


00:31:34.000 --> 00:31:36.310
of supersonic shocks which are formed as


00:31:36.320 --> 00:31:38.310
local gas is being compressed and heated


00:31:38.320 --> 00:31:41.190
in front of the rapidly expanding loes.


00:31:41.200 --> 00:31:43.029
Atoms caught in the shock front are


00:31:43.039 --> 00:31:44.950
radiating invisible light, giving the


00:31:44.960 --> 00:31:47.269
nebula its unique spiderlike shape and


00:31:47.279 --> 00:31:49.669
also contributing to its expansion. The


00:31:49.679 --> 00:31:51.269
star at the center of the Red Spartan


00:31:51.279 --> 00:31:53.430
Nebula is shrouded by a dust chill,


00:31:53.440 --> 00:31:55.190
making its exact properties hard to


00:31:55.200 --> 00:31:57.269
determine. We think it has a surface


00:31:57.279 --> 00:31:58.750
temperature of around


00:31:58.760 --> 00:32:00.870
25,000°, although temperatures of up to


00:32:00.880 --> 00:32:02.630
half a million degrees can't be ruled


00:32:02.640 --> 00:32:04.070
out, which would make it one of the


00:32:04.080 --> 00:32:06.950
hottest white dwarf stars known.


00:32:06.960 --> 00:32:08.789
Now, if you look directly south this


00:32:08.799 --> 00:32:10.389
time of year, you'll find the star


00:32:10.399 --> 00:32:12.710
Polaris Astralis, or more accurately,


00:32:12.720 --> 00:32:15.190
Sigma Octanis, the nearest star to the


00:32:15.200 --> 00:32:16.789
southern celestial pole, and


00:32:16.799 --> 00:32:18.310
consequently the counterpart to the


00:32:18.320 --> 00:32:21.029
north star Polaris. However, Sigma


00:32:21.039 --> 00:32:22.789
Octanis is much harder to see than


00:32:22.799 --> 00:32:25.110
Polaris because it's much fainter.


00:32:25.120 --> 00:32:27.750
Located some 270 light years away, it's


00:32:27.760 --> 00:32:29.750
now an orange giant nearing the end of


00:32:29.760 --> 00:32:32.950
its life. Turning to the southwest just


00:32:32.960 --> 00:32:35.430
above the horizon and we find Kenopus,


00:32:35.440 --> 00:32:37.190
second brightest star in the night sky


00:32:37.200 --> 00:32:40.389
after Sirius. It's located some 310


00:32:40.399 --> 00:32:42.149
lighty years away and is the brightest


00:32:42.159 --> 00:32:43.870
star in the constellation Korean of the


00:32:43.880 --> 00:32:47.350
ke. Kenopus is a super giant some 9


00:32:47.360 --> 00:32:49.669
times the mass of the sun and some 71


00:32:49.679 --> 00:32:50.669
times its


00:32:50.679 --> 00:32:53.590
diameter. The month of June also marks


00:32:53.600 --> 00:32:55.590
the first of two annual encounters with


00:32:55.600 --> 00:32:58.470
a torids meteor shower. The torids are


00:32:58.480 --> 00:33:00.070
generated as the Earth passes through a


00:33:00.080 --> 00:33:02.870
debris stream left by the comet 2P Anki,


00:33:02.880 --> 00:33:04.789
which itself could be pieces of a much


00:33:04.799 --> 00:33:06.549
larger comet that broke apart around


00:33:06.559 --> 00:33:09.110
20,000 to 30,000 years ago, most likely


00:33:09.120 --> 00:33:10.710
following numerous interactions with the


00:33:10.720 --> 00:33:12.549
powerful gravitational field of the


00:33:12.559 --> 00:33:15.269
planet Jupiter. As their name suggests,


00:33:15.279 --> 00:33:17.430
the Torid's radiant or apparent point of


00:33:17.440 --> 00:33:19.509
origin is in the constellation Taurus,


00:33:19.519 --> 00:33:22.070
the bull. The Torid meteor shell is made


00:33:22.080 --> 00:33:24.149
up of larger and more massive material.


00:33:24.159 --> 00:33:26.630
Think of pebbles instead of dust grains.


00:33:26.640 --> 00:33:28.630
Earth passes through this stream twice


00:33:28.640 --> 00:33:30.789
every year. Once in June, then again in


00:33:30.799 --> 00:33:32.310
October when they're referred to as


00:33:32.320 --> 00:33:35.190
Halloween fireballs. The torids release


00:33:35.200 --> 00:33:37.590
material both by normal cometry activity


00:33:37.600 --> 00:33:39.029
and occasionally through close


00:33:39.039 --> 00:33:40.870
encounters with the gravitational tidal


00:33:40.880 --> 00:33:42.909
forces exerted by the Earth and other


00:33:42.919 --> 00:33:45.590
planets. And all this makes the torid


00:33:45.600 --> 00:33:47.350
stream of material the largest in the


00:33:47.360 --> 00:33:49.750
inner solar system. Now, since this


00:33:49.760 --> 00:33:51.669
meteor stream is rather spread out in


00:33:51.679 --> 00:33:53.509
space, planet Earth takes several weeks


00:33:53.519 --> 00:33:55.430
to pass through it, causing an extended


00:33:55.440 --> 00:33:57.110
period of meteor activity compared with


00:33:57.120 --> 00:33:59.110
a much smaller periods of activity by


00:33:59.120 --> 00:34:01.509
other meteor showers. Now, included in


00:34:01.519 --> 00:34:03.430
the Toret stream is a denser flow of


00:34:03.440 --> 00:34:05.990
grally meteors called the Torid Swarm.


00:34:06.000 --> 00:34:07.350
And they're thought to be a ribbon of


00:34:07.360 --> 00:34:10.790
rocks roughly 75 million km by 150 km


00:34:10.800 --> 00:34:12.950
across and held in orbit by Jupiter's


00:34:12.960 --> 00:34:14.470
gravity.


00:34:14.480 --> 00:34:16.470
Now, occasionally, planet Earth passes


00:34:16.480 --> 00:34:18.310
through the larger meteors in this


00:34:18.320 --> 00:34:20.790
denser torid swarm. And one of the


00:34:20.800 --> 00:34:22.869
larger chunks in the torid swarm is now


00:34:22.879 --> 00:34:24.310
thought to have caused the infamous


00:34:24.320 --> 00:34:26.310
Tonguska event in the skies above


00:34:26.320 --> 00:34:29.750
Siberia on June the 30th, 1908. The


00:34:29.760 --> 00:34:31.669
Tangaska event is now believed to have


00:34:31.679 --> 00:34:33.829
been the air burst of a 100 meter wide


00:34:33.839 --> 00:34:36.230
meteor in the skies above the Tangaska


00:34:36.240 --> 00:34:38.149
region of Russia, resulting in mass


00:34:38.159 --> 00:34:40.230
devastation over a 2,000 square


00:34:40.240 --> 00:34:42.550
kilometer region of forest, turning


00:34:42.560 --> 00:34:45.270
trees in matchixs. In fact, the blast


00:34:45.280 --> 00:34:47.669
was so bright it lit up the night sky in


00:34:47.679 --> 00:34:49.430
London a third of the way around the


00:34:49.440 --> 00:34:51.990
planet. The Tanguska event remains the


00:34:52.000 --> 00:34:54.149
largest known Earth impact event of a


00:34:54.159 --> 00:34:57.349
meteor in recorded modern times. Now,


00:34:57.359 --> 00:34:58.630
it's always been considered to be a one


00:34:58.640 --> 00:35:00.470
in a thousand-year event, assuming a


00:35:00.480 --> 00:35:03.109
random distribution of events over time.


00:35:03.119 --> 00:35:04.550
But there's a problem with that because


00:35:04.560 --> 00:35:06.069
of these new studies suggesting the


00:35:06.079 --> 00:35:07.829
event may have been caused by a torid


00:35:07.839 --> 00:35:09.750
swarm meteor. And with the Earth passing


00:35:09.760 --> 00:35:11.589
through the torret swarm periodically,


00:35:11.599 --> 00:35:14.069
it changes the odds considerably. Now,


00:35:14.079 --> 00:35:16.150
if this new stud is correct, the swarm


00:35:16.160 --> 00:35:17.829
heightens the possibility of a cluster


00:35:17.839 --> 00:35:19.829
of large impacts on Earth over a short


00:35:19.839 --> 00:35:21.829
period of time. Now, further


00:35:21.839 --> 00:35:23.910
complicating matters, the June torids


00:35:23.920 --> 00:35:26.470
are actually two separate showers. The


00:35:26.480 --> 00:35:28.069
southern torids are associated with a


00:35:28.079 --> 00:35:30.550
comet 2P Anki, while the northern Torids


00:35:30.560 --> 00:35:33.990
originate from the asteroid 2004 TG10,


00:35:34.000 --> 00:35:35.990
an eccentric kilometer wide asteroid


00:35:36.000 --> 00:35:38.069
classified as a near-Earth object and a


00:35:38.079 --> 00:35:39.750
potentially hazardous asteroid of the


00:35:39.760 --> 00:35:43.109
Apollo group. Something to think about.


00:35:43.119 --> 00:35:44.790
Joining us now for the rest of our tour


00:35:44.800 --> 00:35:46.870
of the night skies of June is science


00:35:46.880 --> 00:35:48.790
editor Jonathan Nally. Good day, Stu.


00:35:48.800 --> 00:35:50.870
Yeah, well, it's June. So, June evenings


00:35:50.880 --> 00:35:53.270
start off with the constellation Orion


00:35:53.280 --> 00:35:55.510
low in the west. So Orion's one of our


00:35:55.520 --> 00:35:56.710
favorite constellations, isn't it? I


00:35:56.720 --> 00:35:58.550
love Orion. Everyone loves Orion. That's


00:35:58.560 --> 00:36:00.390
very easily recognizable. But it is low


00:36:00.400 --> 00:36:03.190
in the west after sunset. And as the


00:36:03.200 --> 00:36:05.510
Earth turns during the evening, it dips


00:36:05.520 --> 00:36:07.270
below the horizon pretty quickly. And by


00:36:07.280 --> 00:36:08.390
the middle of the month, it's actually


00:36:08.400 --> 00:36:09.829
going to be gone. After sunset, you


00:36:09.839 --> 00:36:11.430
won't be able to see it anymore. But it


00:36:11.440 --> 00:36:13.030
will reappear towards the end of the


00:36:13.040 --> 00:36:14.790
year in the eastern sky. And that's when


00:36:14.800 --> 00:36:16.390
Orion appears in the eastern sky at the


00:36:16.400 --> 00:36:17.589
end of the year. That's when you know


00:36:17.599 --> 00:36:18.710
that for people in the southern


00:36:18.720 --> 00:36:20.550
hemisphere, summer is arriving. Or for


00:36:20.560 --> 00:36:21.750
people in the northern hemisphere, they


00:36:21.760 --> 00:36:23.430
know that winter is arriving. So it's


00:36:23.440 --> 00:36:25.750
it's a good sign postpion but yeah you


00:36:25.760 --> 00:36:26.870
get your last glimpse of it now


00:36:26.880 --> 00:36:28.470
basically in the evening the first half


00:36:28.480 --> 00:36:30.310
of June also in the western part of the


00:36:30.320 --> 00:36:32.550
sky there are two bright stars one's


00:36:32.560 --> 00:36:34.069
called Sirius the other one's called


00:36:34.079 --> 00:36:36.790
Prosion Sirius is the brightest star in


00:36:36.800 --> 00:36:39.750
the night sky is the eighth brightest


00:36:39.760 --> 00:36:41.349
still very bright and they have a few


00:36:41.359 --> 00:36:42.630
similarities actually they're both


00:36:42.640 --> 00:36:45.270
binary stars and each of them is a what


00:36:45.280 --> 00:36:47.030
they call a main sequence a normal sort


00:36:47.040 --> 00:36:48.710
of star with a white dwarf going around


00:36:48.720 --> 00:36:50.710
it a white dwarf star and they're both


00:36:50.720 --> 00:36:52.390
within constellations that have the word


00:36:52.400 --> 00:36:54.630
dog In the name Sirius is in the


00:36:54.640 --> 00:36:56.870
constellation Panis Major or the greater


00:36:56.880 --> 00:36:59.349
dog and Croan is in the constellation


00:36:59.359 --> 00:37:01.670
Panis minor or the lesser dog. In the


00:37:01.680 --> 00:37:03.190
southwest there's another bright star


00:37:03.200 --> 00:37:05.109
Canopus. Canopus is my favorite star in


00:37:05.119 --> 00:37:06.870
the whole sky. I reckon it's the second


00:37:06.880 --> 00:37:08.790
brightest star in the night sky. About


00:37:08.800 --> 00:37:10.630
half as bright as Sirius. You only get a


00:37:10.640 --> 00:37:11.910
really good look of it look at it if


00:37:11.920 --> 00:37:13.349
you're in the southern hemisphere. From


00:37:13.359 --> 00:37:15.030
people in the northern hemisphere to the


00:37:15.040 --> 00:37:17.190
lower latitude you can see it uh certain


00:37:17.200 --> 00:37:19.030
times of the year but um from down here


00:37:19.040 --> 00:37:20.790
it's pretty much visible all the time.


00:37:20.800 --> 00:37:22.710
It's actually the most luminous star in


00:37:22.720 --> 00:37:24.310
our neighborhood. It's huge. Yeah, it


00:37:24.320 --> 00:37:26.150
is. It's about 10,000 times brighter


00:37:26.160 --> 00:37:28.790
than our sun, about 10 times its size.


00:37:28.800 --> 00:37:30.790
And fortunately, it is about 310 light


00:37:30.800 --> 00:37:32.950
years away, which is very close in space


00:37:32.960 --> 00:37:34.790
terms, but if it was much closer than


00:37:34.800 --> 00:37:37.510
310 light years away, it would be very,


00:37:37.520 --> 00:37:39.349
very bright indeed. I mean, you I mean,


00:37:39.359 --> 00:37:41.109
if it was, you know, a fraction of that


00:37:41.119 --> 00:37:42.470
distance, you really wouldn't have a


00:37:42.480 --> 00:37:44.710
night sky. Is it the case that Kenopus


00:37:44.720 --> 00:37:47.270
was once closer to our star system than


00:37:47.280 --> 00:37:49.109
Sirius and then it moved away and it


00:37:49.119 --> 00:37:50.950
it's slowly coming back again? I think


00:37:50.960 --> 00:37:52.390
it is the case. Yeah, I think it is the


00:37:52.400 --> 00:37:54.470
case that um the the distances have


00:37:54.480 --> 00:37:56.069
changed a little bit and Kenopus at one


00:37:56.079 --> 00:37:58.150
point was brighter than Sirius I think.


00:37:58.160 --> 00:38:01.349
So you we're moving our souls moving


00:38:01.359 --> 00:38:02.470
through space and Sirius is moving


00:38:02.480 --> 00:38:03.910
through space and Kenopus is moving


00:38:03.920 --> 00:38:05.910
through space. So the distances between


00:38:05.920 --> 00:38:08.069
each other are moving around a bit but


00:38:08.079 --> 00:38:09.910
yeah Kenopus at the moment is not as


00:38:09.920 --> 00:38:11.910
bright as Siri. series is is the is the


00:38:11.920 --> 00:38:13.270
brightest star. But, you know, you go


00:38:13.280 --> 00:38:15.349
out to the to the naked eye, telling one


00:38:15.359 --> 00:38:18.390
star apart of that brightness, telling


00:38:18.400 --> 00:38:21.109
one star apart from another is um it's


00:38:21.119 --> 00:38:23.349
not the easiest thing to do. If you get


00:38:23.359 --> 00:38:24.630
a good look at both and you say, "Yeah,


00:38:24.640 --> 00:38:26.069
yeah, well, series is brighter." But,


00:38:26.079 --> 00:38:27.510
you know, they both are very very


00:38:27.520 --> 00:38:28.870
bright. But yeah, I don't know. Canopus


00:38:28.880 --> 00:38:29.990
is just one of my favorites really. I


00:38:30.000 --> 00:38:30.950
guess because it was one of the first


00:38:30.960 --> 00:38:32.630
stars I identified when I was a kid and


00:38:32.640 --> 00:38:34.630
because it's nice bright star, far down


00:38:34.640 --> 00:38:35.750
the southern style, we sort of got it


00:38:35.760 --> 00:38:37.750
all to our sh sort of thing. So it's


00:38:37.760 --> 00:38:39.910
it's uh just got a sort of a sentimental


00:38:39.920 --> 00:38:41.750
value for me. We're very lucky in the


00:38:41.760 --> 00:38:43.030
southern hemisphere, aren't we? Oh,


00:38:43.040 --> 00:38:43.990
we're super lucky in the southern


00:38:44.000 --> 00:38:45.109
hemisphere. We got lots of bright


00:38:45.119 --> 00:38:46.870
things. We got the uh center of the


00:38:46.880 --> 00:38:48.790
Milky Way galaxy overhead and we got the


00:38:48.800 --> 00:38:50.470
Magelani cloud galaxies. There are


00:38:50.480 --> 00:38:51.589
plenty of good things, which is not to


00:38:51.599 --> 00:38:52.790
say that there aren't plenty of great


00:38:52.800 --> 00:38:54.870
things in the northern sky as well, but


00:38:54.880 --> 00:38:57.190
we um we do have a few extras of down


00:38:57.200 --> 00:38:59.030
here that makes it a bit special. Now


00:38:59.040 --> 00:39:00.870
high in the south about twothirds of the


00:39:00.880 --> 00:39:02.390
way up from the horizon down in the


00:39:02.400 --> 00:39:03.829
south you got the southern cross this


00:39:03.839 --> 00:39:05.670
time of year and it's standing upright


00:39:05.680 --> 00:39:07.510
for a change because a lot of the year


00:39:07.520 --> 00:39:09.270
it's either upside down or on its left


00:39:09.280 --> 00:39:10.550
side or on the right side or whatever


00:39:10.560 --> 00:39:12.470
but round about now it's pretty much


00:39:12.480 --> 00:39:15.109
standing upright nearby you got the pair


00:39:15.119 --> 00:39:17.510
of stars known as the two pointers alpha


00:39:17.520 --> 00:39:19.349
and beta centur we talk about those a


00:39:19.359 --> 00:39:21.670
lot on the show the Milky Way runs right


00:39:21.680 --> 00:39:23.109
through this region of the cross it's


00:39:23.119 --> 00:39:24.550
sort of heading from east to west across


00:39:24.560 --> 00:39:26.150
the sky and there are plenty of star


00:39:26.160 --> 00:39:27.510
clusters and nebula for amateur


00:39:27.520 --> 00:39:29.510
astronomers to enjoy looking along its


00:39:29.520 --> 00:39:31.190
length. Even with a pair of binoculars,


00:39:31.200 --> 00:39:32.390
with a telescope, it's great,


00:39:32.400 --> 00:39:33.349
particularly if you've got one that


00:39:33.359 --> 00:39:35.030
gives you a wide field of view, but just


00:39:35.040 --> 00:39:36.950
binoculars looks really superb along


00:39:36.960 --> 00:39:38.950
there. You do need dark skies, though.


00:39:38.960 --> 00:39:41.109
The city skies make it do make it very,


00:39:41.119 --> 00:39:42.470
very hard with all the light pollution.


00:39:42.480 --> 00:39:44.230
Now, if you do have really dark skies


00:39:44.240 --> 00:39:45.990
and you've got a clear southern horizon,


00:39:46.000 --> 00:39:47.990
you might be able to see two smudges of


00:39:48.000 --> 00:39:49.349
light above the southern horizon. And


00:39:49.359 --> 00:39:50.870
those are these melanic clouds I was


00:39:50.880 --> 00:39:52.550
talking about earlier. These are small


00:39:52.560 --> 00:39:54.870
oddshaped galaxies that are very close


00:39:54.880 --> 00:39:56.310
to the Milky Way. They're they're the


00:39:56.320 --> 00:39:58.390
nearest sizable galaxies to our own and


00:39:58.400 --> 00:39:59.910
you can see them just with the naked


00:39:59.920 --> 00:40:01.589
eye. If you've got dark skies and you


00:40:01.599 --> 00:40:03.190
let your eyes get back into the dark,


00:40:03.200 --> 00:40:04.870
they just look like clouds. They look


00:40:04.880 --> 00:40:07.430
like tiny clouds, hence their name


00:40:07.440 --> 00:40:09.030
clouds. There's actually a bit of a push


00:40:09.040 --> 00:40:12.150
on to rename them, do away with the name


00:40:12.160 --> 00:40:14.230
Mellan because, you know, in keeping


00:40:14.240 --> 00:40:15.670
with the way kings are these days, you


00:40:15.680 --> 00:40:17.750
know, Mr. Mellin, or at least the voyage


00:40:17.760 --> 00:40:19.829
that he was on, was not too kind to some


00:40:19.839 --> 00:40:21.829
of the people and places that they


00:40:21.839 --> 00:40:23.430
visited on their around the world trip.


00:40:23.440 --> 00:40:25.670
So um in the spirit of that some people


00:40:25.680 --> 00:40:27.670
are trying to have that those clouds


00:40:27.680 --> 00:40:29.430
renamed small and large milky clouds or


00:40:29.440 --> 00:40:30.550
something along that line sort of


00:40:30.560 --> 00:40:32.150
similar to the Milky Way. So we'll see


00:40:32.160 --> 00:40:34.310
how far that gets in the northern half


00:40:34.320 --> 00:40:35.829
of the sky as seen from the southern


00:40:35.839 --> 00:40:37.270
hemisphere at least. It does seem a bit


00:40:37.280 --> 00:40:38.870
bare this time of year but there is the


00:40:38.880 --> 00:40:40.950
bright star Arcturus which you can see


00:40:40.960 --> 00:40:42.550
about halfway up from the northern


00:40:42.560 --> 00:40:43.990
horizon. You've got another bright star


00:40:44.000 --> 00:40:45.670
that's reasonably overhead from the


00:40:45.680 --> 00:40:47.750
latitude of Sydney. That star is called


00:40:47.760 --> 00:40:49.910
Spiker. And as the night goes on though,


00:40:49.920 --> 00:40:51.349
you'll see that things have to change


00:40:51.359 --> 00:40:53.109
because the earth is rotating. By


00:40:53.119 --> 00:40:55.589
midnight, Sirius has already set in the


00:40:55.599 --> 00:40:57.030
west. The brightest star has already set


00:40:57.040 --> 00:40:58.309
in the west. And a couple of other


00:40:58.319 --> 00:40:59.750
bright stars have appeared in the north.


00:40:59.760 --> 00:41:02.230
You got Vega and Altter, which are very


00:41:02.240 --> 00:41:03.670
famous stars. They appear in lots of


00:41:03.680 --> 00:41:06.150
science fiction and and TV series, those


00:41:06.160 --> 00:41:07.589
sort of things. And there's another star


00:41:07.599 --> 00:41:09.430
in the southeast actually another one


00:41:09.440 --> 00:41:11.109
like very far in the southeast down the


00:41:11.119 --> 00:41:12.309
southern sky. It's one of these ones


00:41:12.319 --> 00:41:13.589
that you can see really only from the


00:41:13.599 --> 00:41:15.510
southern hemisphere. It's called Akonar.


00:41:15.520 --> 00:41:17.030
And that's actually one of another one


00:41:17.040 --> 00:41:18.390
of my favorite stars. Again, probably


00:41:18.400 --> 00:41:20.230
just got it sort of special because it's


00:41:20.240 --> 00:41:22.230
only visible from the south. And the


00:41:22.240 --> 00:41:23.910
Milky Way, which was stretching, as I


00:41:23.920 --> 00:41:25.190
said, was stretching east to west sort


00:41:25.200 --> 00:41:27.109
of horizontally across the sky. It's now


00:41:27.119 --> 00:41:28.710
stretching from the northeast to the


00:41:28.720 --> 00:41:30.309
southwest sort of diagonally across the


00:41:30.319 --> 00:41:31.829
sky. That's just because the Earth is


00:41:31.839 --> 00:41:32.790
turning and we get a different


00:41:32.800 --> 00:41:34.630
perspective. Now, turning to the


00:41:34.640 --> 00:41:36.630
planets. What have we got? Well, we got


00:41:36.640 --> 00:41:38.550
Jupiter at the moment is out of view.


00:41:38.560 --> 00:41:40.470
It's too close to the sun to be seen.


00:41:40.480 --> 00:41:41.829
That'll be that way for a little while.


00:41:41.839 --> 00:41:43.510
The same goes for Mercury, actually.


00:41:43.520 --> 00:41:45.349
Although, if you are lucky, and by lucky


00:41:45.359 --> 00:41:46.630
I mean if you've got a good clear


00:41:46.640 --> 00:41:48.390
horizon and there's no buildings and


00:41:48.400 --> 00:41:49.829
trees and things in the way, you might


00:41:49.839 --> 00:41:51.910
just be able to spot Mercury very low


00:41:51.920 --> 00:41:53.829
above the western horizon after the sun


00:41:53.839 --> 00:41:56.710
has set in the last week or so of June.


00:41:56.720 --> 00:41:58.950
Other than that, it's um it's very very


00:41:58.960 --> 00:42:00.550
close to the sun and very hard to see.


00:42:00.560 --> 00:42:02.309
Around mid evening time, after it gets


00:42:02.319 --> 00:42:05.109
dark, Mars can be seen about halfway up


00:42:05.119 --> 00:42:06.950
from the horizon very easily. It's a


00:42:06.960 --> 00:42:09.589
sort of a looks like a red star or or an


00:42:09.599 --> 00:42:12.150
orangey reddish kind of star as I say


00:42:12.160 --> 00:42:14.230
about halfway up from the horizon to the


00:42:14.240 --> 00:42:15.589
north if you're viewing from the


00:42:15.599 --> 00:42:17.349
southern hemisphere or to the south if


00:42:17.359 --> 00:42:18.230
you're viewing from the northern


00:42:18.240 --> 00:42:20.230
hemisphere. So see if you can spot that


00:42:20.240 --> 00:42:22.069
one. If you want to spot Saturn, you


00:42:22.079 --> 00:42:23.829
have to stay up a bit later. It rises


00:42:23.839 --> 00:42:25.910
above the eastern horizon about 1:30


00:42:25.920 --> 00:42:27.670
a.m. at the beginning of month and by


00:42:27.680 --> 00:42:30.069
about midnight at the end of June, which


00:42:30.079 --> 00:42:31.990
is a bit past my usual daytime these


00:42:32.000 --> 00:42:33.349
days, but if you're out and about late,


00:42:33.359 --> 00:42:34.550
you should be able to spot it quite


00:42:34.560 --> 00:42:36.150
easily. It's fairly bright. Has a


00:42:36.160 --> 00:42:38.150
slightly yellowish tinge. So, be coming


00:42:38.160 --> 00:42:40.390
up over the horizon about 1:30 a.m. at


00:42:40.400 --> 00:42:41.750
the beginning of the month. And finally,


00:42:41.760 --> 00:42:43.349
we've got Venus, which will also be


00:42:43.359 --> 00:42:44.790
rising over the horizon. It follows


00:42:44.800 --> 00:42:47.589
Saturn, but at around about 3:45 a.m.


00:42:47.599 --> 00:42:49.109
So, you have to stay up very, very late


00:42:49.119 --> 00:42:51.750
for that one. Um, night owls will be


00:42:51.760 --> 00:42:53.270
able to get a view of that, which you


00:42:53.280 --> 00:42:54.950
can't miss Venus doors. I always say


00:42:54.960 --> 00:42:56.390
this, it's so big and bright, you just


00:42:56.400 --> 00:42:57.750
can't miss it. It's the third brightest


00:42:57.760 --> 00:42:59.190
thing in the sky after the sun and the


00:42:59.200 --> 00:43:00.950
moon. So, night time, of course, very


00:43:00.960 --> 00:43:03.030
easy to just spot Venus. You were just


00:43:03.040 --> 00:43:04.550
coming home from the club at that time,


00:43:04.560 --> 00:43:05.750
weren't you? Coming home from the club


00:43:05.760 --> 00:43:07.910
in my dreams, I think. No, I think um


00:43:07.920 --> 00:43:10.470
night owls, those who night shifts and


00:43:10.480 --> 00:43:11.829
those people getting up early for


00:43:11.839 --> 00:43:13.190
morning shifts will be able to spot it.


00:43:13.200 --> 00:43:14.630
It's one of these things actually where


00:43:14.640 --> 00:43:16.230
there are a lot of UFO reports when


00:43:16.240 --> 00:43:17.510
people, you know, say get up early in


00:43:17.520 --> 00:43:18.630
the morning. They're not accustomed to


00:43:18.640 --> 00:43:19.990
being up early in the morning and they


00:43:20.000 --> 00:43:22.150
look out bright white light doesn't seem


00:43:22.160 --> 00:43:23.349
to be moving and they think, "Oh, it's a


00:43:23.359 --> 00:43:25.349
UFO where, you know, it wasn't there


00:43:25.359 --> 00:43:27.109
yesterday." Reality is that it was there


00:43:27.119 --> 00:43:28.390
yesterday. You just didn't notice it.


00:43:28.400 --> 00:43:29.990
And that's Venus. Sometimes Venus is


00:43:30.000 --> 00:43:31.510
visible in the morning's sky and


00:43:31.520 --> 00:43:33.270
sometimes Venus is visible in the


00:43:33.280 --> 00:43:34.710
evening sky and the same goes for


00:43:34.720 --> 00:43:36.710
Mercury. So it does tend to move around


00:43:36.720 --> 00:43:38.550
a little bit, but um there's nothing


00:43:38.560 --> 00:43:39.910
like the view of Venus. And if you get


00:43:39.920 --> 00:43:41.990
out, as we say, sorry, if you go bush,


00:43:42.000 --> 00:43:43.510
uh you know, get away from the cities,


00:43:43.520 --> 00:43:44.470
get away from the city lights and


00:43:44.480 --> 00:43:46.069
everything. So you get really dark


00:43:46.079 --> 00:43:48.550
skies, you know, when Venus is big and


00:43:48.560 --> 00:43:50.150
bright and up like that, you know, throw


00:43:50.160 --> 00:43:51.750
shadows. It's bright enough to throw


00:43:51.760 --> 00:43:53.030
shadows. You can see where you're going


00:43:53.040 --> 00:43:55.109
just by the light of Venus alone. It's


00:43:55.119 --> 00:43:56.470
uh it's really quite remarkable.


00:43:56.480 --> 00:43:57.750
Interesting thing about Venus. Found


00:43:57.760 --> 00:44:00.150
this from a old Isaac Azimov book. Now,


00:44:00.160 --> 00:44:01.510
I don't know whether he was the first


00:44:01.520 --> 00:44:03.109
one to come up with this idea or not,


00:44:03.119 --> 00:44:05.910
but um I I read it. Yeah, an old cuz he


00:44:05.920 --> 00:44:08.230
used to write science essays and science


00:44:08.240 --> 00:44:09.910
columns and science books and things as


00:44:09.920 --> 00:44:11.990
well as his science fiction and he he


00:44:12.000 --> 00:44:13.349
said that you know because we've got the


00:44:13.359 --> 00:44:15.430
moon going around the earth right which


00:44:15.440 --> 00:44:17.349
is a fairly big moon compared to the


00:44:17.359 --> 00:44:19.910
size of the earth moons it's a quarter


00:44:19.920 --> 00:44:21.430
of the size of the earth it's huge yeah


00:44:21.440 --> 00:44:22.470
some people might call it a double


00:44:22.480 --> 00:44:24.309
planet system in a way it's a very large


00:44:24.319 --> 00:44:26.390
moon was just a little bit closer the


00:44:26.400 --> 00:44:29.349
barry center would be outside the earth


00:44:29.359 --> 00:44:31.670
and under those circumstances then we


00:44:31.680 --> 00:44:33.510
would be a binary system like Pluto and


00:44:33.520 --> 00:44:34.790
Sharon that's exactly You're right. Now


00:44:34.800 --> 00:44:36.390
that now what he proposed in this


00:44:36.400 --> 00:44:38.309
article was and this could have changed


00:44:38.319 --> 00:44:39.670
the cause of history actually if this


00:44:39.680 --> 00:44:41.990
had happened was that if the moon hadn't


00:44:42.000 --> 00:44:44.390
formed around Earth if instead it had


00:44:44.400 --> 00:44:47.270
formed in orbit around Venus and Venus


00:44:47.280 --> 00:44:49.670
is about the same size as the Earth then


00:44:49.680 --> 00:44:51.990
at the distance of Venus when the moon


00:44:52.000 --> 00:44:54.309
was at its furthest from Venus you would


00:44:54.319 --> 00:44:56.550
be able to see just with the unaded eye


00:44:56.560 --> 00:44:58.390
you would be able to see Venus and its


00:44:58.400 --> 00:45:00.470
moon theoretical moon or hypothetical


00:45:00.480 --> 00:45:02.309
moon separated on the night sky and you


00:45:02.319 --> 00:45:04.390
would see that moon's position changing


00:45:04.400 --> 00:45:05.829
from night to night and you would be


00:45:05.839 --> 00:45:07.510
drawn to the inescapable conclusion that


00:45:07.520 --> 00:45:10.390
that small dot was circling the larger


00:45:10.400 --> 00:45:12.390
dot, right? So something was going


00:45:12.400 --> 00:45:14.150
around something else and of course we


00:45:14.160 --> 00:45:15.670
remember from our history about things,


00:45:15.680 --> 00:45:17.270
you know, were thing things going around


00:45:17.280 --> 00:45:18.550
the earth or was the earth going around


00:45:18.560 --> 00:45:20.150
the sun. So the sun going around the


00:45:20.160 --> 00:45:21.430
earth, earth going around the sun and


00:45:21.440 --> 00:45:23.470
for a long time of course it was


00:45:23.480 --> 00:45:26.870
people and before him. Yeah. Yeah. Well,


00:45:26.880 --> 00:45:28.950
see the you know it took until Galileo


00:45:28.960 --> 00:45:30.470
looking through his telescope to see


00:45:30.480 --> 00:45:31.589
that the moons were going around


00:45:31.599 --> 00:45:33.190
Jupiter. or something else, you know,


00:45:33.200 --> 00:45:34.870
and yet it moves and something's going


00:45:34.880 --> 00:45:37.109
around Jupiter. Well, if if the moon had


00:45:37.119 --> 00:45:39.430
formed the orbit around Venus, then we


00:45:39.440 --> 00:45:41.190
we would have known since antiquity, you


00:45:41.200 --> 00:45:43.109
know, since since, you know, prehistoric


00:45:43.119 --> 00:45:44.950
times that something was going around


00:45:44.960 --> 00:45:46.630
something else out there in space. And


00:45:46.640 --> 00:45:48.630
therefore, we would have known that not


00:45:48.640 --> 00:45:50.470
everything goes around the earth. In


00:45:50.480 --> 00:45:52.230
other words, this whole idea that the


00:45:52.240 --> 00:45:53.750
earth being the center of everything,


00:45:53.760 --> 00:45:55.349
which sort of held us back for a very


00:45:55.359 --> 00:45:57.750
long time, uh might not have taken hold


00:45:57.760 --> 00:46:00.230
or at least um not as widely taken hold


00:46:00.240 --> 00:46:02.470
or for as long. So just one of those


00:46:02.480 --> 00:46:04.550
accidents of nature that the the moon


00:46:04.560 --> 00:46:06.309
formed in orbit around the earth rather


00:46:06.319 --> 00:46:08.230
than Venus. Interesting, isn't it? For a


00:46:08.240 --> 00:46:10.150
long time, people used to think that


00:46:10.160 --> 00:46:12.470
because Venus is covered in clouds and


00:46:12.480 --> 00:46:13.910
it's a bit closer to the sun than the


00:46:13.920 --> 00:46:15.990
Earth. Then those clouds must mean lots


00:46:16.000 --> 00:46:17.990
of rain. Lots of rain means lots of


00:46:18.000 --> 00:46:19.670
water on the ground. Lots of water on


00:46:19.680 --> 00:46:21.270
the ground means lots of trees could


00:46:21.280 --> 00:46:23.270
have grown. Lots of forests. Probably


00:46:23.280 --> 00:46:24.950
tropical rainforest would have grown


00:46:24.960 --> 00:46:26.790
there. Yeah, because Venus is close to


00:46:26.800 --> 00:46:27.670
the sun. Therefore, it would have been


00:46:27.680 --> 00:46:29.030
warmer. So yeah, tropical rain forest


00:46:29.040 --> 00:46:31.190
and probably dinosaurs. dinosaurs was


00:46:31.200 --> 00:46:32.550
the next thing that came up. You're


00:46:32.560 --> 00:46:34.390
right. Yes. Some scientists even


00:46:34.400 --> 00:46:35.829
postulated that, well, if you've got


00:46:35.839 --> 00:46:37.349
tropical rainforest, you've probably got


00:46:37.359 --> 00:46:38.870
dinosaurs. How they reached that


00:46:38.880 --> 00:46:40.150
conclusion, I don't know, but that was


00:46:40.160 --> 00:46:41.750
Yeah, that was very common back in the


00:46:41.760 --> 00:46:43.589
50s and 60s. A lot of scientists


00:46:43.599 --> 00:46:45.349
supported that idea. It was it was it


00:46:45.359 --> 00:46:46.870
was speculation and I mean, it was sort


00:46:46.880 --> 00:46:48.470
of a very uneducated guess, but you


00:46:48.480 --> 00:46:49.990
know, you can sort of understand. It's


00:46:50.000 --> 00:46:51.430
like the canals on Mars, isn't it? Yeah,


00:46:51.440 --> 00:46:54.150
the canals on Mars. See, here's the it's


00:46:54.160 --> 00:46:55.910
hard for people these days, I suppose,


00:46:55.920 --> 00:46:58.309
to think about this, but you go back to


00:46:58.319 --> 00:47:00.230
the turn of the 19th, 20th century, you


00:47:00.240 --> 00:47:01.990
know, go back to the year 1900 or


00:47:02.000 --> 00:47:04.150
whatever. It was widely assumed that


00:47:04.160 --> 00:47:05.829
there would be life on the other planets


00:47:05.839 --> 00:47:07.430
because if there's life on Earth, why


00:47:07.440 --> 00:47:08.710
wouldn't there be life on other planets?


00:47:08.720 --> 00:47:10.150
Because we didn't know what those other


00:47:10.160 --> 00:47:11.670
planets were like back then. We didn't


00:47:11.680 --> 00:47:14.069
have the technology to really establish


00:47:14.079 --> 00:47:16.710
uh what the atmospheres were made of um


00:47:16.720 --> 00:47:18.550
and what the temperatures might be, all


00:47:18.560 --> 00:47:19.990
that sort of thing. At least we're not


00:47:20.000 --> 00:47:22.470
in great precision. And so even when the


00:47:22.480 --> 00:47:25.109
first NASA spacecraft were getting to um


00:47:25.119 --> 00:47:27.190
Mars, it was you know still people were


00:47:27.200 --> 00:47:28.630
thinking well that's going to show


00:47:28.640 --> 00:47:29.990
things on Mars, you know, might show


00:47:30.000 --> 00:47:31.510
vegetation or whatever. But then the


00:47:31.520 --> 00:47:33.030
first picture started coming back which


00:47:33.040 --> 00:47:35.190
just showed a desert world with craters


00:47:35.200 --> 00:47:38.230
and things. So um for a long time people


00:47:38.240 --> 00:47:40.390
just assumed that there there was going


00:47:40.400 --> 00:47:41.990
to be life on the other other world.


00:47:42.000 --> 00:47:43.430
Then we started to learn, you know, that


00:47:43.440 --> 00:47:44.870
Mars is actually really cold. It's got a


00:47:44.880 --> 00:47:47.349
thin atmosphere and Venus has got a


00:47:47.359 --> 00:47:49.030
runaway greenhouse effect. So it's very


00:47:49.040 --> 00:47:50.470
very hot and the air pressure would be


00:47:50.480 --> 00:47:52.069
very very intense. You know about 90


00:47:52.079 --> 00:47:55.030
atmosphere and temperatures of over 400°


00:47:55.040 --> 00:47:57.109
Celsius 450 something degrees Celsius


00:47:57.119 --> 00:47:59.030
and possible sulfuric acid rain from the


00:47:59.040 --> 00:48:02.150
clouds. So snow on the cloud tops by the


00:48:02.160 --> 00:48:03.990
way we've got a we've got a far more


00:48:04.000 --> 00:48:06.150
sophisticated idea of what things are


00:48:06.160 --> 00:48:07.430
like out there now. But yeah back in the


00:48:07.440 --> 00:48:08.630
back in the early days when we didn't


00:48:08.640 --> 00:48:10.870
really know people just assume. So but


00:48:10.880 --> 00:48:12.550
you know goodness knows how many things


00:48:12.560 --> 00:48:14.550
we take for granted as being true right


00:48:14.560 --> 00:48:17.349
now this year in 2025 which 100 years


00:48:17.359 --> 00:48:19.829
from now or 50 years from now uh will be


00:48:19.839 --> 00:48:22.150
considered complete nonsense. So um I'm


00:48:22.160 --> 00:48:23.990
not critical of um people who thought


00:48:24.000 --> 00:48:26.230
various things in in past times when


00:48:26.240 --> 00:48:28.309
they were had some reason to think that


00:48:28.319 --> 00:48:29.750
might have been it's it's when you get


00:48:29.760 --> 00:48:31.349
people who just totally ignore the


00:48:31.359 --> 00:48:33.030
evidence or you know try and work their


00:48:33.040 --> 00:48:34.630
way around the evidence. So for


00:48:34.640 --> 00:48:36.870
instance, PL look at finding his canals


00:48:36.880 --> 00:48:38.309
on Mars when no one else could see them,


00:48:38.319 --> 00:48:39.430
but he just sort of stuck with it


00:48:39.440 --> 00:48:40.790
because he was he was sure that there


00:48:40.800 --> 00:48:42.069
were canals on Mars and no one else


00:48:42.079 --> 00:48:43.910
could see them. So um that that's when


00:48:43.920 --> 00:48:45.589
you have problems. Well, the problem was


00:48:45.599 --> 00:48:47.349
he didn't translate Chaperelli's


00:48:47.359 --> 00:48:49.270
original comments correctly. Chaperelli


00:48:49.280 --> 00:48:50.950
was talking about canali, but he didn't


00:48:50.960 --> 00:48:52.710
mean canals. He meant channels.


00:48:52.720 --> 00:48:54.230
Something like water channels or river,


00:48:54.240 --> 00:48:55.270
that kind of thing. Yeah. They got


00:48:55.280 --> 00:48:57.670
translated into canals, which in English


00:48:57.680 --> 00:48:59.829
means an artificial. Yeah. Well, they


00:48:59.839 --> 00:49:01.829
were building a huge canal network in


00:49:01.839 --> 00:49:03.430
England at the time, weren't they? Yeah.


00:49:03.440 --> 00:49:05.670
Yeah. And um and he was he was


00:49:05.680 --> 00:49:06.870
essentially seeing what he wanted to


00:49:06.880 --> 00:49:08.549
see. He got it into his mind and and


00:49:08.559 --> 00:49:10.390
that was the end of it. And um yeah,


00:49:10.400 --> 00:49:11.829
well that I mean that's that's a that's


00:49:11.839 --> 00:49:13.349
just a human failing, isn't it really?


00:49:13.359 --> 00:49:14.950
And on that philosophical note, Stuart,


00:49:14.960 --> 00:49:16.230
we just solved all the world's problems


00:49:16.240 --> 00:49:18.150
once again. Aren't we good? And and I'll


00:49:18.160 --> 00:49:19.349
see you next month. That's science


00:49:19.359 --> 00:49:36.589
editor Jonathan Nally and this is


00:49:36.599 --> 00:49:39.829
Spacetime and that's the show for now.


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