Mapping the Milky Way: New Insights, Martian Mysteries, and Psyche’s Thruster Troubles

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Kind: captions
Language: en

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This is Spacetime Series 28, episode 56


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for broadcast on the 9th of May,


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2025. Coming up on Spaceime, a stunning


00:00:09.679 --> 00:00:12.709
new map of the nearby Milky Way galaxy,


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searching for the dark in Martian light,


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and NASA investigating problems with the


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Psyche spacecraft's thruster system. 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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NASA's New Horizon spacecraft has


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provided astronomers with an important


00:00:47.680 --> 00:00:50.150
new ultraviolet map of our galaxy, the


00:00:50.160 --> 00:00:52.470
Milky Way. The spectacular new


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observations reported in the


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astronomical journal use a specific


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ultraviolet wavelength, shedding new


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light on structures and processes in the


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galactic region surrounding our solar


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system. In fact, these new landmark


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observations are providing astronomers


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with their first clear view of the sky


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surrounding the solar system at these


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wavelengths, and they're revealing both


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new characteristics of that sky and


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refuting old ideas. The study's lead


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author Randy Gladston from the Southwest


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Research Institute says the new findings


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are showing hot interstellar gas bubbles


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like the one our solar systems embedded


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within may actually be regions of


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enhanced hydrogen gas emissions at


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wavelengths known as lyman alpha. Lyman


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alpha is a specific wavelength of


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ultraviolet light emitted and scattered


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by hydrogen atoms. It's especially


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useful to astronomers studying distant


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stars, galaxies, and the interstellar


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medium as it can help detect the


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composition, temperature, and movement


00:01:47.520 --> 00:01:49.910
of these distant objects. During its


00:01:49.920 --> 00:01:52.069
initial journey to Pluto, New Horizons


00:01:52.079 --> 00:01:54.230
collected baseline data about lime and


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alpha emissions using its Alice


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ultraviolet spectrograph. Spectrograph


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split light into various wavelengths of


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colors, and Alice specializes in the far


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ultraviolet wavelength band. After the


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spacecraft's primary flyby of the dwarf


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planet Pluto and its binary partner


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Sharon, scientists used Alice to make


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broader and more frequent surveys of


00:02:14.160 --> 00:02:16.470
lime and alpha emissions as new horizons


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traveled further from the sun. These


00:02:18.959 --> 00:02:20.869
surveys included an extensive set of


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scans mapping roughly 83% of the sky. To


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isolate emissions from the galaxy,


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astronomers modeled scattered solar


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limema alpha emissions and then


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subtracted them from the specttograph's


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data. The results indicate a roughly


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uniform background lime and alpha sky


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brightness 10 times stronger than what


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was expected from previous estimates.


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Gladston says the results point to the


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emission and scattering of lime and


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alpha photons by hydrogen atoms in the


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shell of a hot bubble known as surround


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our solar system nearby stars. That


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bubble was formed by nearby supernova


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events millions of years ago. The study


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also found no evidence that a hydrogen


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wall thought to surround the sun's


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heliosphere substantially contributes to


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the observed lime and alpha signal.


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Astronomers had theorized that a wall of


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interstellar hydrogen atoms would


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accumulate as they encountered the edge


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of the heliosphere. The vast region of


00:03:11.519 --> 00:03:13.750
space encapsulating our solar system


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dominated by the solar wind. However,


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the new horizon's data saw nothing to


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indicate the wall is an important source


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of lime and alpha emissions. This is


00:03:23.720 --> 00:03:26.550
spaceime still to come. Searching for


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the dark in the Martian light and NASA


00:03:29.120 --> 00:03:30.789
mission managers are investigating a


00:03:30.799 --> 00:03:32.309
major problem with the electric


00:03:32.319 --> 00:03:34.070
propulsion system aboard its Psyche


00:03:34.080 --> 00:03:36.149
spacecraft. All that and more still to


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come on


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[Music]


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Spaceime. This episode of Spacetime is


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[Music]


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NASA's Mars Perseverance rover has been


00:05:12.240 --> 00:05:14.070
busy over the past week continuing its


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exploration of the lower witch Hazel


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Hill outcrop exposed on the edge of the


00:05:17.840 --> 00:05:20.469
Jezro crater rim. The formations


00:05:20.479 --> 00:05:22.710
composed of alternating light and dark


00:05:22.720 --> 00:05:25.029
layers of rock and mission managers have


00:05:25.039 --> 00:05:26.710
been busy trying to understand the


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makeup and relationship of these layers.


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A few weeks ago, they sampled one of the


00:05:31.360 --> 00:05:33.110
light tone layers at a place they've


00:05:33.120 --> 00:05:35.189
named Maine River. They discovered it


00:05:35.199 --> 00:05:36.950
was made up of very small clasts or


00:05:36.960 --> 00:05:39.590
fragments of rocks and minerals. Since


00:05:39.600 --> 00:05:41.350
then, scientists have learned that the


00:05:41.360 --> 00:05:43.350
darker layers tend to be composed of


00:05:43.360 --> 00:05:45.430
larger classs compared to the lighter


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layers, and they've been searching for a


00:05:47.120 --> 00:05:49.110
place to sample this coarser grain rock


00:05:49.120 --> 00:05:51.510
type. Sometimes these coarser grain


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rocks also contain sphererals which are


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of great interest to scientists because


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they provide clues about the very


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processes that form the layered rock


00:05:58.800 --> 00:06:00.710
formations in the first place.


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Perseverance first looked at a dark


00:06:02.639 --> 00:06:05.189
layer at punchon rock using its abrasion


00:06:05.199 --> 00:06:07.749
tool. They then examined another dark


00:06:07.759 --> 00:06:09.350
layer at a formation known as wreck


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apple but couldn't find a suitable space


00:06:11.280 --> 00:06:14.230
to araid. So while scientists searched


00:06:14.240 --> 00:06:16.230
for other locations to study the coarse


00:06:16.240 --> 00:06:18.390
grain units and sphererals, Perseverance


00:06:18.400 --> 00:06:20.390
drove further south to a place known as


00:06:20.400 --> 00:06:23.029
Port Anson. Port Anson's intriguing


00:06:23.039 --> 00:06:25.110
because from orbit it showed a clear


00:06:25.120 --> 00:06:27.029
contact between the lighter layers of


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witch hazel hill and a distinct unit


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below it. And although the rocks below


00:06:31.919 --> 00:06:33.990
the poansen contact point do show


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interesting compositional differences


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with those of witch hazel hill, they


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weren't the coarse grain rocks


00:06:38.240 --> 00:06:40.469
scientists were looking for. Still, they


00:06:40.479 --> 00:06:42.629
did perform an abrasion test there at a


00:06:42.639 --> 00:06:44.550
location they've named Strong Island


00:06:44.560 --> 00:06:46.469
before driving back up north for what


00:06:46.479 --> 00:06:48.230
hopefully will be another attempt at


00:06:48.240 --> 00:06:51.029
investigating the coarser grain rocks.


00:06:51.039 --> 00:06:53.309
Needless to say, we'll keep you


00:06:53.319 --> 00:06:56.629
informed. This is Spaceime. Still to


00:06:56.639 --> 00:06:58.230
come, NASA mission managers


00:06:58.240 --> 00:07:00.150
investigating a serious problem with the


00:07:00.160 --> 00:07:01.909
electric propulsion system aboard its


00:07:01.919 --> 00:07:04.550
Psyche spacecraft. And we explore the


00:07:04.560 --> 00:07:06.950
constellation Scorpius, the spectacular


00:07:06.960 --> 00:07:09.909
M6 and M7 open star clusters, and the


00:07:09.919 --> 00:07:12.870
ETAs meteor shower produced by Hal's


00:07:12.880 --> 00:07:15.870
Comet in the May edition of Skywatch.


00:07:15.880 --> 00:07:23.080
[Music]




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NASA mission managers are investigating


00:07:32.160 --> 00:07:33.670
a problem with the electric propulsion


00:07:33.680 --> 00:07:36.230
system aboard the Saki spacecraft.


00:07:36.240 --> 00:07:37.990
Launched on a Falcon Heavy rocket back


00:07:38.000 --> 00:07:42.550
in October 2023, the 2,68 kg probe is on


00:07:42.560 --> 00:07:44.629
a mission to explore the metallic main


00:07:44.639 --> 00:07:47.270
belt asteroid 16 Psyche in order to


00:07:47.280 --> 00:07:49.189
learn more about the origins of


00:07:49.199 --> 00:07:52.629
planetary cores. 16 Sakis, the heaviest


00:07:52.639 --> 00:07:55.189
known Mtype asteroid, and it may be the


00:07:55.199 --> 00:07:57.670
exposed iron core of a protolanet, the


00:07:57.680 --> 00:07:59.270
remnant of a violent collision with


00:07:59.280 --> 00:08:01.350
another object that stripped this body


00:08:01.360 --> 00:08:04.070
off its metal and crust. The spacecraft


00:08:04.080 --> 00:08:06.629
will eventually spend 817 Earth days


00:08:06.639 --> 00:08:09.430
orbiting the strange 226 km wide


00:08:09.440 --> 00:08:11.830
metallic world. But it's got to get


00:08:11.840 --> 00:08:13.990
there first. Mission managers with


00:08:14.000 --> 00:08:15.670
NASA's Jet Propulsion Laboratory in


00:08:15.680 --> 00:08:17.830
Pasin, California, say the spacecraft's


00:08:17.840 --> 00:08:19.909
electric thrusters shut down on April


00:08:19.919 --> 00:08:21.990
the 1st when pressure fell in the line


00:08:22.000 --> 00:08:24.070
that feeds Xeon propellant to the Hall


00:08:24.080 --> 00:08:26.469
effect thrusters. The pressure dropped


00:08:26.479 --> 00:08:29.510
from 248 kilopascals down to 179,


00:08:29.520 --> 00:08:31.909
causing the thrusters to stop working.


00:08:31.919 --> 00:08:33.670
The probe turned on its hall effect


00:08:33.680 --> 00:08:36.389
thrusters in May 2024, which combined


00:08:36.399 --> 00:08:38.389
with a gravity assist Mars flyby


00:08:38.399 --> 00:08:40.230
scheduled for May next year will allow


00:08:40.240 --> 00:08:43.149
the probe to arrive at Psyche in August


00:08:43.159 --> 00:08:45.509
2029. Now, right now, there's not too


00:08:45.519 --> 00:08:47.750
much to worry about. Psyche can continue


00:08:47.760 --> 00:08:49.829
to coast until the middle of June before


00:08:49.839 --> 00:08:51.470
there's a significant effect on its


00:08:51.480 --> 00:08:53.430
trajectory. Right now, potential


00:08:53.440 --> 00:08:55.350
solutions include switching to a backup


00:08:55.360 --> 00:08:57.670
propellant line. It's the first major


00:08:57.680 --> 00:08:59.269
problem with the spacecraft which had


00:08:59.279 --> 00:09:00.949
been working normally since its long


00:09:00.959 --> 00:09:03.350
delayed launch. See, the project had


00:09:03.360 --> 00:09:04.870
suffered a series of development


00:09:04.880 --> 00:09:07.190
problems during its construction phase.


00:09:07.200 --> 00:09:09.509
These included the co pandemic and


00:09:09.519 --> 00:09:11.829
software testing delays which pushed


00:09:11.839 --> 00:09:13.430
back the launch date from the originally


00:09:13.440 --> 00:09:17.190
slated August 2022 by more than a year.


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This is spaceime


00:09:23.340 --> 00:09:35.110
[Music]


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And time now to turn our eyes to the


00:09:36.880 --> 00:09:38.790
skies and check out the celestial sphere


00:09:38.800 --> 00:09:42.150
for the month of May on Skywatch. May is


00:09:42.160 --> 00:09:43.829
the fifth month of the year in both the


00:09:43.839 --> 00:09:46.949
Julian and Gagorian calendars. The month


00:09:46.959 --> 00:09:49.350
was named for the Greek goddess Maya who


00:09:49.360 --> 00:09:51.269
was identified with the Roman era


00:09:51.279 --> 00:09:53.430
goddess of fertility Bonadia whose


00:09:53.440 --> 00:09:55.750
festival was held in May. But I guess


00:09:55.760 --> 00:09:57.110
more importantly for many of our


00:09:57.120 --> 00:09:59.350
listeners, May typically marks the start


00:09:59.360 --> 00:10:01.670
of summer vacation season in the United


00:10:01.680 --> 00:10:04.389
States and Canada. Let's start our tour


00:10:04.399 --> 00:10:06.550
of the night skies by looking east where


00:10:06.560 --> 00:10:08.389
you'll see the constellation Scorpius,


00:10:08.399 --> 00:10:11.190
the Scorpion. In Greek mythology, the


00:10:11.200 --> 00:10:13.190
constellation was named after Scorpius,


00:10:13.200 --> 00:10:14.790
who was sent to Earth by the goddess


00:10:14.800 --> 00:10:17.030
Gaia, in order to slay Orion, the


00:10:17.040 --> 00:10:18.949
Hunter, after he boasted that he could


00:10:18.959 --> 00:10:21.750
kill all the animals on Earth. Scorpius


00:10:21.760 --> 00:10:24.870
stung Orion in the shoulder. But Orion's


00:10:24.880 --> 00:10:27.670
life was spared by Ofious, the healer,


00:10:27.680 --> 00:10:29.430
and it was placed in the heavens along


00:10:29.440 --> 00:10:31.750
with Scorpius, who continues to pursue


00:10:31.760 --> 00:10:34.630
him for eternity. Orion the hunter has


00:10:34.640 --> 00:10:36.949
become the hunted forever with Scorpius


00:10:36.959 --> 00:10:39.030
rising in the east this time of year to


00:10:39.040 --> 00:10:41.350
triumphantly chase and defeat Orion who


00:10:41.360 --> 00:10:44.310
sets in the west. Meanwhile, Ofucius the


00:10:44.320 --> 00:10:46.069
healer rises in the east following


00:10:46.079 --> 00:10:48.470
behind Scorpius to chase and crush him


00:10:48.480 --> 00:10:50.630
into the earth as the scorpion sets in


00:10:50.640 --> 00:10:53.829
the west. And so this ancient story


00:10:53.839 --> 00:10:55.750
continues to play out in the heavens


00:10:55.760 --> 00:10:58.710
year after year. Interestingly, parts of


00:10:58.720 --> 00:11:01.430
the story predate the Greeks with Orion


00:11:01.440 --> 00:11:03.670
known in ancient Egypt as Osiris, the


00:11:03.680 --> 00:11:05.870
god of the underworld and of


00:11:05.880 --> 00:11:07.990
regeneration. The brightest star in


00:11:08.000 --> 00:11:10.870
Scorpius is Alpha Scorpio or Antares,


00:11:10.880 --> 00:11:13.350
the scorpion's heart. In ancient Greek,


00:11:13.360 --> 00:11:15.829
the name Antares means the equal arrival


00:11:15.839 --> 00:11:18.630
of Mars, the god of war. That's because


00:11:18.640 --> 00:11:20.790
its golden orange appearance is similar


00:11:20.800 --> 00:11:22.949
to that of the red planet, and it passes


00:11:22.959 --> 00:11:26.630
very close to Mars every 780 years.


00:11:26.640 --> 00:11:28.790
easily seen with the unaded eye and


00:11:28.800 --> 00:11:32.069
Tares is some 550 lighty years away but


00:11:32.079 --> 00:11:34.670
it looks so bright because it's around


00:11:34.680 --> 00:11:37.750
57,500 times as luminous as the sun and


00:11:37.760 --> 00:11:40.269
is one of the largest known stars in the


00:11:40.279 --> 00:11:44.230
universe. Ant is a red super giant about


00:11:44.240 --> 00:11:47.110
18 times the mass and 883 times the


00:11:47.120 --> 00:11:49.829
diameter of the sun. Were it placed


00:11:49.839 --> 00:11:51.990
where the sun is in our solar system, it


00:11:52.000 --> 00:11:53.590
would engulf all the terrestrial


00:11:53.600 --> 00:11:55.590
planets, Mercury, Venus, Earth, and


00:11:55.600 --> 00:11:57.910
Mars. And its visible surface would


00:11:57.920 --> 00:12:00.949
extend almost as far out as Jupiter. A


00:12:00.959 --> 00:12:02.630
lightyear is about 10 trillion


00:12:02.640 --> 00:12:04.949
kilometers. The distance a photon can


00:12:04.959 --> 00:12:08.310
travel in a year at 300,000 km/s, the


00:12:08.320 --> 00:12:10.150
speed of light in a vacuum, and the


00:12:10.160 --> 00:12:12.710
ultimate speed limit of the universe.


00:12:12.720 --> 00:12:15.110
Astronomers believe Antaris began life


00:12:15.120 --> 00:12:17.110
around 12 million years ago as a


00:12:17.120 --> 00:12:19.829
spectrotype O or B blue star.


00:12:19.839 --> 00:12:22.150
Astronomers describe stars in terms of


00:12:22.160 --> 00:12:24.389
spectral types, a classification system


00:12:24.399 --> 00:12:25.870
based on temperature and


00:12:25.880 --> 00:12:27.829
characteristics. The hottest, most


00:12:27.839 --> 00:12:29.910
massive, and most luminous stars are


00:12:29.920 --> 00:12:32.710
known as spectrotype O blue stars.


00:12:32.720 --> 00:12:34.710
They're followed by spectrotype B blue


00:12:34.720 --> 00:12:37.269
white stars. Then spectrotype A white


00:12:37.279 --> 00:12:39.829
stars, spectrotype F whitish yellow


00:12:39.839 --> 00:12:42.550
stars, spectrotype G yellow stars.


00:12:42.560 --> 00:12:44.230
That's where our sun fits in. Then


00:12:44.240 --> 00:12:46.790
there's spectrotype K orange stars. And


00:12:46.800 --> 00:12:48.949
the coolest and least massive stars are


00:12:48.959 --> 00:12:52.069
known as spectrotype M red stars. Each


00:12:52.079 --> 00:12:54.069
spectral classification system can also


00:12:54.079 --> 00:12:56.550
be subdivided using a numeric digit to


00:12:56.560 --> 00:12:58.389
represent temperature with zero being


00:12:58.399 --> 00:13:01.190
the hottest and nine the coolest. And


00:13:01.200 --> 00:13:02.870
then you add a Roman numeral to


00:13:02.880 --> 00:13:05.509
represent luminosity. So put it all


00:13:05.519 --> 00:13:07.829
together and you can describe our sun as


00:13:07.839 --> 00:13:12.470
being a G2V or G25 yellow dwarf star,


00:13:12.480 --> 00:13:14.910
one of millions spread across our


00:13:14.920 --> 00:13:17.269
galaxy. Also included in the stellar


00:13:17.279 --> 00:13:19.430
classification system are special types


00:13:19.440 --> 00:13:21.829
LT and Y which are assigned to failed


00:13:21.839 --> 00:13:24.069
stars known as brown dwarves. Some of


00:13:24.079 --> 00:13:25.990
which were actually born as spectrotype


00:13:26.000 --> 00:13:28.550
M red stars but became brown dwarves


00:13:28.560 --> 00:13:31.030
after losing some of their mass. Brown


00:13:31.040 --> 00:13:33.030
dwarves fit into a unique category


00:13:33.040 --> 00:13:34.629
between the largest planets, which are


00:13:34.639 --> 00:13:36.710
about 13 times the mass of Jupiter, and


00:13:36.720 --> 00:13:38.870
the smallest spectrotype M red dwarf


00:13:38.880 --> 00:13:41.430
stars, which are about 75 to 80 times


00:13:41.440 --> 00:13:44.990
the mass of Jupiter, or 0.08 solar


00:13:45.000 --> 00:13:47.750
masses. Like the similarsized red giant


00:13:47.760 --> 00:13:50.150
Betalers in the constellation Orion,


00:13:50.160 --> 00:13:52.230
Antares will almost certainly end its


00:13:52.240 --> 00:13:54.870
life as a spectacular type 2 or core


00:13:54.880 --> 00:13:57.350
collapse supernova, probably sometime


00:13:57.360 --> 00:13:59.910
within the next 100,000 years or so.


00:13:59.920 --> 00:14:01.750
When it does explode, it'll appear as


00:14:01.760 --> 00:14:03.509
bright as the full moon for several


00:14:03.519 --> 00:14:05.670
months on end and will be clearly


00:14:05.680 --> 00:14:07.750
visible during daylight hours here on


00:14:07.760 --> 00:14:10.550
Earth. Antares has a companion star,


00:14:10.560 --> 00:14:15.110
Antares B, located between 224 and 529


00:14:15.120 --> 00:14:16.870
astronomical units away from the


00:14:16.880 --> 00:14:19.430
primary. An astronomical unit is the


00:14:19.440 --> 00:14:21.030
average distance between the Earth and


00:14:21.040 --> 00:14:23.350
the Sun, which is about 150 million


00:14:23.360 --> 00:14:27.189
kilome or 8.3 light minutes. Spectral


00:14:27.199 --> 00:14:29.750
analysis of Antares B indicates it's


00:14:29.760 --> 00:14:31.269
pulling a lot of material off its


00:14:31.279 --> 00:14:33.629
bloated red super giant


00:14:33.639 --> 00:14:36.870
companion. Located near Antares is the


00:14:36.880 --> 00:14:40.150
M4 globular cluster. Globular clusters


00:14:40.160 --> 00:14:42.150
are tight balls densely packed with


00:14:42.160 --> 00:14:44.310
thousands to millions of stars which


00:14:44.320 --> 00:14:46.389
were either all originally formed at the


00:14:46.399 --> 00:14:47.990
same time from the collapse of the same


00:14:48.000 --> 00:14:49.990
molecular gas and dust cloud or


00:14:50.000 --> 00:14:52.310
alternatively their galactic centers.


00:14:52.320 --> 00:14:54.150
the remains of ancient galaxies that


00:14:54.160 --> 00:14:55.750
have been merged into the Milky Way


00:14:55.760 --> 00:14:59.269
galaxy over billions of years. M4 is


00:14:59.279 --> 00:15:01.110
composed of a million or so stars


00:15:01.120 --> 00:15:03.269
originally born some 12 billion years


00:15:03.279 --> 00:15:06.550
ago. The M4 globular cluster is located


00:15:06.560 --> 00:15:09.509
some 7,200 light years away, making it


00:15:09.519 --> 00:15:11.310
one of the nearest globular clusters to


00:15:11.320 --> 00:15:13.829
Earth. Easily seen through a pair of


00:15:13.839 --> 00:15:16.069
small binoculars, it covers an area of


00:15:16.079 --> 00:15:18.470
the sky as seen from Earth as big as the


00:15:18.480 --> 00:15:21.030
full moon. Astronomers estimate there


00:15:21.040 --> 00:15:23.829
are some 150 or so globular clusters


00:15:23.839 --> 00:15:26.189
orbiting in the halo of the Milky


00:15:26.199 --> 00:15:28.790
Way. Located near the tail of the


00:15:28.800 --> 00:15:31.189
scorpion are two open star clusters


00:15:31.199 --> 00:15:34.710
known as M6 and M7. Open star clusters


00:15:34.720 --> 00:15:36.389
are loosely bound groups of a few


00:15:36.399 --> 00:15:38.550
thousand stars which all originally


00:15:38.560 --> 00:15:40.389
formed from the same molecular gas and


00:15:40.399 --> 00:15:42.470
dust cloud at the same time but are not


00:15:42.480 --> 00:15:45.350
as densely bound as globular clusters.


00:15:45.360 --> 00:15:47.189
Open clusters generally survive for a


00:15:47.199 --> 00:15:49.030
few hundred million years with the most


00:15:49.040 --> 00:15:50.870
massive ones surviving for maybe a few


00:15:50.880 --> 00:15:53.590
billion years. Now, in contrast, the far


00:15:53.600 --> 00:15:56.150
more massive globular clusters exert far


00:15:56.160 --> 00:15:57.990
stronger gravitational attraction on


00:15:58.000 --> 00:15:59.590
their members, which is why they can


00:15:59.600 --> 00:16:02.389
survive so much longer. M6, which is


00:16:02.399 --> 00:16:04.389
also known as the butterfly cluster, is


00:16:04.399 --> 00:16:06.870
some 12 light years across and located


00:16:06.880 --> 00:16:09.430
about 1,600 lighty years away. It


00:16:09.440 --> 00:16:11.430
contains around 80 stars which are all


00:16:11.440 --> 00:16:13.590
less than 100 million years old which is


00:16:13.600 --> 00:16:17.189
quite young in cosmic terms. The M7 or


00:16:17.199 --> 00:16:19.590
Tom cluster is named after the famous


00:16:19.600 --> 00:16:21.189
Greek astronomer and mathematician


00:16:21.199 --> 00:16:24.710
Claudius Tom. It's about 980 light years


00:16:24.720 --> 00:16:27.509
away and is far more dispersed than M6


00:16:27.519 --> 00:16:29.870
covering an area around 25 lighty years


00:16:29.880 --> 00:16:32.949
across. And at around 200 million years,


00:16:32.959 --> 00:16:35.590
it's about twice as old.


00:16:35.600 --> 00:16:39.030
By the way, the M in terms like M4, M6,


00:16:39.040 --> 00:16:42.470
and M7 are abbreviations for Messier in


00:16:42.480 --> 00:16:43.910
honor of the 18th century French


00:16:43.920 --> 00:16:45.590
astronomer Charles Messier, who


00:16:45.600 --> 00:16:47.670
developed an astronomical catalog of


00:16:47.680 --> 00:16:50.629
fuzzy, nebulous objects in the skies.


00:16:50.639 --> 00:16:53.269
See, Messier was a comet hunter, and he


00:16:53.279 --> 00:16:55.990
compiled a list of 103 fuzzy objects


00:16:56.000 --> 00:16:58.150
which weren't comets, and so from his


00:16:58.160 --> 00:17:00.790
perspective could be ignored. Later,


00:17:00.800 --> 00:17:02.470
other astronomers added additional


00:17:02.480 --> 00:17:04.390
celestial objects to the list, bringing


00:17:04.400 --> 00:17:06.510
the present catalog up to


00:17:06.520 --> 00:17:09.669
110. Our solar system, in fact, most of


00:17:09.679 --> 00:17:11.510
the stars we see when we look up in the


00:17:11.520 --> 00:17:13.909
night sky, are located in the Milky Way


00:17:13.919 --> 00:17:17.429
galaxy's Orion arm. The Orion arm, also


00:17:17.439 --> 00:17:19.590
known as the Orion spur or the Orion


00:17:19.600 --> 00:17:21.590
Signis arm, depending on which name you


00:17:21.600 --> 00:17:24.710
prefer, is some 3,500 lighty years wide


00:17:24.720 --> 00:17:27.829
and around 10,000 lighty years long. The


00:17:27.839 --> 00:17:30.110
Orion arm is named after the Orion


00:17:30.120 --> 00:17:31.990
constellation which is one of the most


00:17:32.000 --> 00:17:33.830
prominent constellations in the southern


00:17:33.840 --> 00:17:35.350
hemisphere summer and northern


00:17:35.360 --> 00:17:37.990
hemisphere winter. Some of the brightest


00:17:38.000 --> 00:17:40.150
and most famous celestial objects in the


00:17:40.160 --> 00:17:43.350
constellation include bettle riel the


00:17:43.360 --> 00:17:45.750
stars of the Orion belt and the Orion


00:17:45.760 --> 00:17:48.789
nebula all located within the Orion arm.


00:17:48.799 --> 00:17:50.789
The Orion arm is located between the


00:17:50.799 --> 00:17:53.029
Karina Sagittarius arm which is more


00:17:53.039 --> 00:17:54.710
towards the galactic center from our


00:17:54.720 --> 00:17:57.029
position and the Perseus arm which is


00:17:57.039 --> 00:17:58.470
more towards the outer edge of the


00:17:58.480 --> 00:18:00.390
galaxy from our point of view. The


00:18:00.400 --> 00:18:02.710
Perseus arm is one of the two major arms


00:18:02.720 --> 00:18:04.789
of the Milky Way. The other being the


00:18:04.799 --> 00:18:07.830
Scutum Centurus arm. Long thought of as


00:18:07.840 --> 00:18:10.470
a minor structure, a spur if you will


00:18:10.480 --> 00:18:12.549
between the two longer adjacent arms,


00:18:12.559 --> 00:18:15.190
Perseus and Karina Sagittarius. Evidence


00:18:15.200 --> 00:18:17.909
was presented in mid 2013 that the Orion


00:18:17.919 --> 00:18:19.590
arm might actually be a branch of the


00:18:19.600 --> 00:18:21.830
Perseus arm or possibly a completely


00:18:21.840 --> 00:18:24.549
independent arm segment itself. Within


00:18:24.559 --> 00:18:27.190
the Orion arm, our solar system, the


00:18:27.200 --> 00:18:28.549
sun, the Earth, and all the other


00:18:28.559 --> 00:18:30.630
planets we know are located close to the


00:18:30.640 --> 00:18:32.870
inner rim in what's known as the local


00:18:32.880 --> 00:18:35.270
bubble. About halfway along the Orion


00:18:35.280 --> 00:18:37.830
arm's length, approximately 26,000 light


00:18:37.840 --> 00:18:40.230
years from the galactic center. The


00:18:40.240 --> 00:18:42.070
local bubble is a cavity in the


00:18:42.080 --> 00:18:44.070
interstellar medium in the Orion arm


00:18:44.080 --> 00:18:45.909
containing among other things the local


00:18:45.919 --> 00:18:47.830
interstellar cloud which contains our


00:18:47.840 --> 00:18:50.870
solar system and the G-Cloud. It's at


00:18:50.880 --> 00:18:53.669
least 300 light years across and it has


00:18:53.679 --> 00:18:56.950
a neutral hydrogen density of just 0.05


00:18:56.960 --> 00:18:59.830
atoms per cm. That's just 1/10enth of


00:18:59.840 --> 00:19:01.590
the average for the interstellar medium


00:19:01.600 --> 00:19:03.990
across the Milky Way and about a sixth


00:19:04.000 --> 00:19:06.310
that of the local interstellar cloud.


00:19:06.320 --> 00:19:08.470
The hot diffused gas in the local bubble


00:19:08.480 --> 00:19:10.710
emits X-rays and is the result of a


00:19:10.720 --> 00:19:12.870
supernova that exploded sometime during


00:19:12.880 --> 00:19:15.750
the past 10 to 20 million years. It was


00:19:15.760 --> 00:19:17.270
once thought that the most likely


00:19:17.280 --> 00:19:18.630
candidate for the remains of this


00:19:18.640 --> 00:19:21.350
supernova was Jiminga, a pulsar in the


00:19:21.360 --> 00:19:24.390
constellation Gemini. However, later it


00:19:24.400 --> 00:19:26.789
was suggested that modable supernova in


00:19:26.799 --> 00:19:29.270
a subgroup B1 of the Plleades moving


00:19:29.280 --> 00:19:31.350
group was more likely responsible


00:19:31.360 --> 00:19:33.990
becoming a remnant super shell. Our


00:19:34.000 --> 00:19:35.590
solar system has been traveling through


00:19:35.600 --> 00:19:37.590
this region of space occupied by the


00:19:37.600 --> 00:19:39.750
local bubble for the last 5 to 10


00:19:39.760 --> 00:19:42.710
million years. Its current location is


00:19:42.720 --> 00:19:43.990
in what's known as the local


00:19:44.000 --> 00:19:46.710
interstellar cloud. A minor region of


00:19:46.720 --> 00:19:48.549
slightly denser material within the


00:19:48.559 --> 00:19:50.950
bubble. The cloud formed when the local


00:19:50.960 --> 00:19:52.789
bubble and another bubble called the


00:19:52.799 --> 00:19:55.590
loop one bubble met. Gas within the


00:19:55.600 --> 00:19:57.510
local interstellar cloud has a density


00:19:57.520 --> 00:20:01.350
of about 0.3 atoms per cm. From what we


00:20:01.360 --> 00:20:02.870
can tell, the local bubble isn't


00:20:02.880 --> 00:20:05.190
spherical, but seems to be narrower in


00:20:05.200 --> 00:20:07.270
the galactic plane, becoming somewhat


00:20:07.280 --> 00:20:09.430
egg- shaped or elliptical, and may even


00:20:09.440 --> 00:20:11.029
become wider above and below the


00:20:11.039 --> 00:20:13.190
galactic plane, becoming shaped more


00:20:13.200 --> 00:20:15.830
like an hourglass. And it's not alone.


00:20:15.840 --> 00:20:17.990
It's abuting other bubbles of lesser


00:20:18.000 --> 00:20:20.150
dense interstellar medium, including the


00:20:20.160 --> 00:20:22.710
loop one bubble. The loop one bubble was


00:20:22.720 --> 00:20:25.029
created by supernova and stellar winds


00:20:25.039 --> 00:20:27.270
in the Scorpio Centurus Association,


00:20:27.280 --> 00:20:29.990
some 500 light years from the sun. The


00:20:30.000 --> 00:20:32.070
loop one bubble also contains the star


00:20:32.080 --> 00:20:34.789
antures that we spoke about earlier.


00:20:34.799 --> 00:20:36.950
Astronomers have identified several well


00:20:36.960 --> 00:20:38.870
I guess you'd call them tunnels which


00:20:38.880 --> 00:20:40.789
connect the cavities of the local bubble


00:20:40.799 --> 00:20:42.710
with that of the loop one bubble.


00:20:42.720 --> 00:20:44.390
Collectively they've been referred to as


00:20:44.400 --> 00:20:46.630
the lupus tunnel. Other bubbles which


00:20:46.640 --> 00:20:48.470
are adjacent to our local bubble and


00:20:48.480 --> 00:20:50.630
known as the loop 2 bubble and the loop


00:20:50.640 --> 00:20:52.870
three bubble. Looks like astronomers


00:20:52.880 --> 00:20:54.470
still have a problem when it comes to


00:20:54.480 --> 00:20:56.710
thinking up cool names.


00:20:56.720 --> 00:20:58.710
Also visible this month is the ETA


00:20:58.720 --> 00:21:01.270
awards meteor shower which is generated


00:21:01.280 --> 00:21:03.029
as the Earth passes through the dust and


00:21:03.039 --> 00:21:05.990
debris trail left behind by Hal's comet.


00:21:06.000 --> 00:21:08.630
Comet P1's a well-known short period


00:21:08.640 --> 00:21:10.310
comet which visits the inner solar


00:21:10.320 --> 00:21:14.310
system every 75 to 76 years. The 15


00:21:14.320 --> 00:21:16.390
kilometer wide mountain of rock and ice


00:21:16.400 --> 00:21:18.230
will make its next close-up appearance


00:21:18.240 --> 00:21:20.230
in 2061.


00:21:20.240 --> 00:21:21.830
It's named in honor of the British


00:21:21.840 --> 00:21:25.029
astronomer Edmund Halley who in 1705


00:21:25.039 --> 00:21:26.870
after examining ancient Chinese,


00:21:26.880 --> 00:21:28.950
Babylonian, and medieval European


00:21:28.960 --> 00:21:30.870
records successfully predicted its


00:21:30.880 --> 00:21:32.190
return in


00:21:32.200 --> 00:21:36.149
1758. However, he died in 1742 before


00:21:36.159 --> 00:21:38.549
his prediction could be confirmed. The


00:21:38.559 --> 00:21:40.630
comet's highly elliptical and elongated


00:21:40.640 --> 00:21:42.549
orbit takes it from between the orbits


00:21:42.559 --> 00:21:44.789
of Mercury and Venus out almost as far


00:21:44.799 --> 00:21:47.510
as the orbit of Pluto. Hali's orbit is


00:21:47.520 --> 00:21:49.830
in retrograde, meaning it orbits the sun


00:21:49.840 --> 00:21:51.430
in the opposite direction to the


00:21:51.440 --> 00:21:53.669
planets, that is clockwise from above


00:21:53.679 --> 00:21:56.390
the sun's northern pole. This retrograde


00:21:56.400 --> 00:21:58.070
orbit results in it having one of the


00:21:58.080 --> 00:21:59.990
highest velocities relative to the Earth


00:22:00.000 --> 00:22:02.070
of any object in the solar system,


00:22:02.080 --> 00:22:06.230
traveling at some 70.56 km/s, or if you


00:22:06.240 --> 00:22:08.190
prefer,


00:22:08.200 --> 00:22:11.510
254,016 km hour, as well as the


00:22:11.520 --> 00:22:14.310
Etoacrids meteor shower every May. Hal's


00:22:14.320 --> 00:22:16.789
comet also produces the Orionids meteor


00:22:16.799 --> 00:22:19.350
shower in late October. Astronomers


00:22:19.360 --> 00:22:21.510
think comet Halley was originally a long


00:22:21.520 --> 00:22:23.510
period comet which took thousands of


00:22:23.520 --> 00:22:25.110
years to travel to the inner solar


00:22:25.120 --> 00:22:27.190
system from the ought cloud but was


00:22:27.200 --> 00:22:28.950
gravitationally perturbed into its


00:22:28.960 --> 00:22:30.950
current orbit by close encounters with


00:22:30.960 --> 00:22:33.990
the giant outer planets. The cloud is a


00:22:34.000 --> 00:22:36.310
hypothetical sphere of comets and


00:22:36.320 --> 00:22:38.710
asteroids beyond the heliosphere. a


00:22:38.720 --> 00:22:40.630
mixture of vagabonds from the solar


00:22:40.640 --> 00:22:43.029
system and objects from deep space which


00:22:43.039 --> 00:22:44.470
have been collected by the sun's


00:22:44.480 --> 00:22:47.029
gravitational pole. Occasionally, as the


00:22:47.039 --> 00:22:49.510
sun passes by another star, an orcloud


00:22:49.520 --> 00:22:51.590
object will get perturbed and be flung


00:22:51.600 --> 00:22:54.070
towards the inner solar system. The


00:22:54.080 --> 00:22:56.470
Acrid's meteor shower runs from the 19th


00:22:56.480 --> 00:22:59.110
of April through to the 28th of May,


00:22:59.120 --> 00:23:01.430
peaking around May the 5th with around


00:23:01.440 --> 00:23:04.149
55 meteors an hour, making it one of the


00:23:04.159 --> 00:23:05.990
southern hemisphere's best celestial


00:23:06.000 --> 00:23:09.750
showers. However, back in 1975, they


00:23:09.760 --> 00:23:12.789
were running 95 meteors an hour. And in


00:23:12.799 --> 00:23:16.390
1980, it was up to 110. Even better, the


00:23:16.400 --> 00:23:18.390
bright yellow meteors often appear as


00:23:18.400 --> 00:23:21.270
streaks known as trains. As their name


00:23:21.280 --> 00:23:23.590
suggests, they radiate out from the


00:23:23.600 --> 00:23:25.430
direction of the constellation Aquarius


00:23:25.440 --> 00:23:27.990
and the star Eta Aquiry. Just look


00:23:28.000 --> 00:23:29.590
towards the east after midnight and


00:23:29.600 --> 00:23:32.470
before dawn for the best view. And


00:23:32.480 --> 00:23:34.230
joining us now for the rest of our tour


00:23:34.240 --> 00:23:36.549
of the May night skies and skywatch is


00:23:36.559 --> 00:23:38.630
science writer Jonathan Alli. Good day


00:23:38.640 --> 00:23:40.710
Stuart. Yes, it's May. So the nights are


00:23:40.720 --> 00:23:42.230
definitely getting longer and colder in


00:23:42.240 --> 00:23:43.750
the part of the planet where I live as


00:23:43.760 --> 00:23:45.350
we head towards winter. But you know


00:23:45.360 --> 00:23:46.630
despite the cold, this is actually a


00:23:46.640 --> 00:23:48.230
great time for stargazing if you live


00:23:48.240 --> 00:23:49.750
where I am in the southern hemisphere as


00:23:49.760 --> 00:23:51.669
there are lots of great southern


00:23:51.679 --> 00:23:53.750
constellations visible. So some of the


00:23:53.760 --> 00:23:54.870
ones that you know you got to be far


00:23:54.880 --> 00:23:57.029
south to see such as the southern cross


00:23:57.039 --> 00:23:58.470
which at the moment is standing pretty


00:23:58.480 --> 00:24:00.549
much upright high in the south in the


00:24:00.559 --> 00:24:02.149
middle part of the evening to its left


00:24:02.159 --> 00:24:03.909
we've got these two bright stars in the


00:24:03.919 --> 00:24:06.070
constellation centurus that's alpha and


00:24:06.080 --> 00:24:08.310
beta centuri and astronomers call them


00:24:08.320 --> 00:24:10.310
the two pointers because if you draw an


00:24:10.320 --> 00:24:11.909
imaginary line between them and then


00:24:11.919 --> 00:24:13.510
keep the line going it more or less


00:24:13.520 --> 00:24:15.350
points towards the southern cross. Those


00:24:15.360 --> 00:24:16.950
two stars are really quite bright and


00:24:16.960 --> 00:24:18.390
prominent and they're close together. So


00:24:18.400 --> 00:24:20.390
people often spot them before they spot


00:24:20.400 --> 00:24:21.830
the southern cross. Yeah, I was using


00:24:21.840 --> 00:24:23.350
them as a marker to help me find the


00:24:23.360 --> 00:24:24.710
southern cross. Yeah. Yeah. And look,


00:24:24.720 --> 00:24:26.070
they're they're very bright compared to


00:24:26.080 --> 00:24:28.070
the the star. The stars in Southern


00:24:28.080 --> 00:24:30.549
Cross are not particularly dim, but it's


00:24:30.559 --> 00:24:32.710
a small constellation and when people go


00:24:32.720 --> 00:24:34.710
out try to find the southern cross, they


00:24:34.720 --> 00:24:35.990
um they're looking for something bigger.


00:24:36.000 --> 00:24:37.430
So, they don't really notice the cross


00:24:37.440 --> 00:24:38.710
at first. So, if you find these two


00:24:38.720 --> 00:24:39.990
pointer stars and then you just draw


00:24:40.000 --> 00:24:41.669
this do this trick of drawing the line


00:24:41.679 --> 00:24:43.110
and extending it a bit, then you think,


00:24:43.120 --> 00:24:44.470
"Oh, that's the southern that crosses


00:24:44.480 --> 00:24:46.149
it." So, uh yeah, they're very they're


00:24:46.159 --> 00:24:47.830
quite handy. Now, in the vicinity of the


00:24:47.840 --> 00:24:49.110
cross, there are two interesting sites


00:24:49.120 --> 00:24:50.710
to see, although you probably do need


00:24:50.720 --> 00:24:54.149
some non city dark skies to get a good


00:24:54.159 --> 00:24:55.350
view of them. The first of them is


00:24:55.360 --> 00:24:57.669
what's called the Cold Sack Nebula,


00:24:57.679 --> 00:24:59.830
which is a dark patch in the Milky Way


00:24:59.840 --> 00:25:01.190
right next to the Southern Cross. It's


00:25:01.200 --> 00:25:02.549
quite large. It's It's Yeah, it's


00:25:02.559 --> 00:25:03.909
probably about half the size or more of


00:25:03.919 --> 00:25:05.430
the Southern Cross. Yeah, this is quite


00:25:05.440 --> 00:25:07.510
large actually. It's a huge cloud of gas


00:25:07.520 --> 00:25:10.470
and dust almost 600 light years away.


00:25:10.480 --> 00:25:12.390
And because it's a very thick cloud of


00:25:12.400 --> 00:25:13.990
gas and dust, it's blocking out the


00:25:14.000 --> 00:25:16.390
light of the stars behind it. So, um,


00:25:16.400 --> 00:25:17.990
you know, years and years and years ago


00:25:18.000 --> 00:25:19.669
before photography started to come


00:25:19.679 --> 00:25:21.590
along, astronomers weren't really sure


00:25:21.600 --> 00:25:23.990
was this was this a hole in the Milky


00:25:24.000 --> 00:25:25.190
Way, and we're looking straight through


00:25:25.200 --> 00:25:28.470
to out to the other side, or is this a


00:25:28.480 --> 00:25:30.149
big dark something that's blocking the


00:25:30.159 --> 00:25:32.390
light from the stars behind? And yes, it


00:25:32.400 --> 00:25:35.190
is a big dark blob that is blocking the


00:25:35.200 --> 00:25:36.549
light of the stars behind it. There are


00:25:36.559 --> 00:25:38.149
stars in front of it, too, but not too


00:25:38.159 --> 00:25:40.149
many. They're not very um obvious to the


00:25:40.159 --> 00:25:42.070
naked eye. But you probably do need dark


00:25:42.080 --> 00:25:44.390
stars to see the um the Colac Nebula. I


00:25:44.400 --> 00:25:46.310
struggle to see it from where I am in


00:25:46.320 --> 00:25:48.230
suburbia. The other object of interest


00:25:48.240 --> 00:25:50.230
is a small star cluster called the jewel


00:25:50.240 --> 00:25:52.630
box, which is located a bit below and to


00:25:52.640 --> 00:25:54.789
the left of the leftmost star in the


00:25:54.799 --> 00:25:56.630
southern cross. Now, if you live in the


00:25:56.640 --> 00:25:58.149
city, you might just be able to make it


00:25:58.159 --> 00:25:59.669
out with your own eyes, but a pair of


00:25:59.679 --> 00:26:01.510
binoculars will definitely help. And


00:26:01.520 --> 00:26:02.950
through them, you'll see a pretty


00:26:02.960 --> 00:26:05.669
collection, maybe half a dozen, seven or


00:26:05.679 --> 00:26:07.750
eight, 10 stars perhaps, of different


00:26:07.760 --> 00:26:09.269
colors. That's why it's called a jewel


00:26:09.279 --> 00:26:10.950
box. And they're all closely packed


00:26:10.960 --> 00:26:12.630
together. All up, there are actually


00:26:12.640 --> 00:26:14.470
about a hundred stars in this cluster,


00:26:14.480 --> 00:26:15.590
but you're not going to see all of those


00:26:15.600 --> 00:26:17.110
with a pair of binoculars. You need big


00:26:17.120 --> 00:26:18.870
telescope to start see dozens and dozens


00:26:18.880 --> 00:26:20.470
of them. But it is really, really pretty


00:26:20.480 --> 00:26:21.990
and it's quite an easy one to see and


00:26:22.000 --> 00:26:23.830
it's fairly bright as star clusters go.


00:26:23.840 --> 00:26:25.149
That's much further away than the


00:26:25.159 --> 00:26:27.590
Colac's about 600 lighty years away.


00:26:27.600 --> 00:26:29.750
This little jewel box cluster is 6 and a


00:26:29.760 --> 00:26:32.310
half thousand light years away. Now to


00:26:32.320 --> 00:26:33.669
the right of the southern cross, as we


00:26:33.679 --> 00:26:35.110
look down to the south, you've got three


00:26:35.120 --> 00:26:36.870
large constellations. You've got Karina,


00:26:36.880 --> 00:26:39.029
VA, and Papus. all part of the Milky Way


00:26:39.039 --> 00:26:40.950
and they're full of glorious starfields


00:26:40.960 --> 00:26:42.870
and lots of nebulan things, including


00:26:42.880 --> 00:26:44.950
one called the Great Nebula in Karina.


00:26:44.960 --> 00:26:47.430
Now, this one rivals or in some people's


00:26:47.440 --> 00:26:50.630
opinions even exceed the splendor of the


00:26:50.640 --> 00:26:53.190
more famous nebula, the Orion Nebula,


00:26:53.200 --> 00:26:55.430
which is very easy to to make out


00:26:55.440 --> 00:26:57.029
because, you know, you can you need to


00:26:57.039 --> 00:26:58.630
see you need to be down south here to


00:26:58.640 --> 00:27:00.390
see the Karina. You got to be down south


00:27:00.400 --> 00:27:02.870
and it is a large fuzzy patch which you


00:27:02.880 --> 00:27:04.710
can see with your own eyes if you're


00:27:04.720 --> 00:27:06.710
under dark skies. But if you can get a


00:27:06.720 --> 00:27:08.630
telescope onto this region, uh, it just


00:27:08.640 --> 00:27:10.789
lets you see so much more. It really is


00:27:10.799 --> 00:27:13.269
is quite spectacular. It the extent of


00:27:13.279 --> 00:27:14.950
it, if you were able to see the whole


00:27:14.960 --> 00:27:16.470
thing with your just with your own eyes,


00:27:16.480 --> 00:27:18.310
it would be, you know, several times the


00:27:18.320 --> 00:27:20.630
width of the full moon. It's it's very


00:27:20.640 --> 00:27:22.390
large in the night sky. We don't notice


00:27:22.400 --> 00:27:25.669
it normally because it is fuzzy and


00:27:25.679 --> 00:27:28.390
faint. And most of us live in light


00:27:28.400 --> 00:27:31.909
polluted cities. So you you've got


00:27:31.919 --> 00:27:33.750
Buckley's chance as we say in Australia


00:27:33.760 --> 00:27:36.549
of seeing anything like this from light


00:27:36.559 --> 00:27:38.149
polluted light polluted skies. So you


00:27:38.159 --> 00:27:39.990
need to get somewhere dark and let your


00:27:40.000 --> 00:27:42.390
eyes get dark adapted. Now in the nearby


00:27:42.400 --> 00:27:44.149
constellation, same sort of well the


00:27:44.159 --> 00:27:45.549
other side of the cross really got


00:27:45.559 --> 00:27:47.909
centurus. You can find the globular star


00:27:47.919 --> 00:27:49.909
cluster Omega Centuri. Now this one is


00:27:49.919 --> 00:27:52.470
quite easy to see. It's visible as a


00:27:52.480 --> 00:27:54.950
just a what looks like a fuzgy star to


00:27:54.960 --> 00:27:57.029
the unaded eye. You got a pair of


00:27:57.039 --> 00:27:58.950
binoculars. It'll it'll reveal it


00:27:58.960 --> 00:27:59.750
depending on the size of your


00:27:59.760 --> 00:28:01.269
binoculars. It should reveal it to be


00:28:01.279 --> 00:28:04.870
like a small gray ball, just a tiny gray


00:28:04.880 --> 00:28:07.669
ball, but a telescope will show its true


00:28:07.679 --> 00:28:10.630
nature, which is a huge globe of


00:28:10.640 --> 00:28:13.029
seemingly countless stars, a globular


00:28:13.039 --> 00:28:14.789
star cluster, it's called it's called.


00:28:14.799 --> 00:28:16.789
It's an really impressive site. And if


00:28:16.799 --> 00:28:19.110
you get on the internet and have a look


00:28:19.120 --> 00:28:21.990
for Omega Centuri, you'll see what I


00:28:22.000 --> 00:28:23.830
mean. It is the most in fact, it's it's


00:28:23.840 --> 00:28:25.510
the best of these globular star clusters


00:28:25.520 --> 00:28:26.870
in the whole sky. It's the biggest and


00:28:26.880 --> 00:28:28.950
best and brightest. It really is very,


00:28:28.960 --> 00:28:31.190
very impressive. Now, low down in the


00:28:31.200 --> 00:28:32.789
eastern sky at mid evening, you got the


00:28:32.799 --> 00:28:34.430
constellation Scorpius above the


00:28:34.440 --> 00:28:37.110
horizon. This, for me, is a true


00:28:37.120 --> 00:28:38.470
indication that the middle of the year


00:28:38.480 --> 00:28:41.350
is upon us because Scorpius is us in the


00:28:41.360 --> 00:28:42.389
southern hemisphere a winter


00:28:42.399 --> 00:28:43.750
constellation. For our friends in the


00:28:43.760 --> 00:28:46.389
north, it's a summer constellation. So,


00:28:46.399 --> 00:28:48.630
as the evening goes on, the full extent


00:28:48.640 --> 00:28:50.389
of Scorpius will come up and and be


00:28:50.399 --> 00:28:52.149
visible. Scorpius is one of the rare


00:28:52.159 --> 00:28:53.590
constellations. It actually looks like


00:28:53.600 --> 00:28:55.590
what it's supposed to be. uh you know


00:28:55.600 --> 00:28:57.029
you've got triang constellation


00:28:57.039 --> 00:28:58.710
triangulum which is a triangle right so


00:28:58.720 --> 00:29:00.549
that's not too hard the southern cross


00:29:00.559 --> 00:29:02.230
does look like a southern cross but


00:29:02.240 --> 00:29:04.070
scorpius really does look like a


00:29:04.080 --> 00:29:05.990
scorpion it traces out the shape of a


00:29:06.000 --> 00:29:08.230
scorpion really really well it's it's


00:29:08.240 --> 00:29:09.269
just one of those things that just


00:29:09.279 --> 00:29:10.389
happen to be in the right part of the


00:29:10.399 --> 00:29:12.149
galaxy to see these stars from this


00:29:12.159 --> 00:29:14.789
point of view and uh yeah it really does


00:29:14.799 --> 00:29:16.310
the constellation right next to it


00:29:16.320 --> 00:29:18.470
famous Sagittarius got no idea what that


00:29:18.480 --> 00:29:19.590
looks like you know it's one of the join


00:29:19.600 --> 00:29:21.190
the dot things but when we do look at


00:29:21.200 --> 00:29:23.510
Sagittarius which was which we you will


00:29:23.520 --> 00:29:26.070
see if you stay past midnight, you'll


00:29:26.080 --> 00:29:27.669
see Sagittarius come up or if you wait


00:29:27.679 --> 00:29:28.950
for a month or two, it'll be in the


00:29:28.960 --> 00:29:30.789
evening sky. When we look towards


00:29:30.799 --> 00:29:32.310
Sagittarius, we are looking into the


00:29:32.320 --> 00:29:34.470
direction of the center of our Milky Way


00:29:34.480 --> 00:29:36.149
galaxy. And this is actually one of the


00:29:36.159 --> 00:29:39.029
main reasons why meteor stargazing is is


00:29:39.039 --> 00:29:40.470
considered so good by amateur


00:29:40.480 --> 00:29:42.470
astronomers because we have all the


00:29:42.480 --> 00:29:44.470
starfields and the deep sky objects of


00:29:44.480 --> 00:29:47.350
the Milky Way central region to enjoy


00:29:47.360 --> 00:29:48.870
because we're looking right into the


00:29:48.880 --> 00:29:50.630
core. There's lots and lots of stuff. If


00:29:50.640 --> 00:29:51.669
you look in the opposite direction,


00:29:51.679 --> 00:29:53.350
you're looking towards the outskirts of


00:29:53.360 --> 00:29:56.470
the galaxy and there's perhaps the left


00:29:56.480 --> 00:29:57.990
sea. So there's a lot of stuff


00:29:58.000 --> 00:30:00.070
concentrated in towards the center of


00:30:00.080 --> 00:30:02.549
our galaxy during the middle of the


00:30:02.559 --> 00:30:04.789
year. And because Sagittarius and it


00:30:04.799 --> 00:30:06.149
sort of surrounding constellations are


00:30:06.159 --> 00:30:07.990
located south of celestial equator, it


00:30:08.000 --> 00:30:09.669
means that those of us who live south of


00:30:09.679 --> 00:30:11.430
the earthly equator get the best view of


00:30:11.440 --> 00:30:13.269
it because from the latitude to where I


00:30:13.279 --> 00:30:15.269
live, it's basically right overhead at


00:30:15.279 --> 00:30:17.430
nighttime. So, you know, you when things


00:30:17.440 --> 00:30:18.549
are right overhead, you're looking


00:30:18.559 --> 00:30:19.909
through the thinnest part of the Earth's


00:30:19.919 --> 00:30:21.430
atmosphere. If things are down on the


00:30:21.440 --> 00:30:23.029
horizon, you're looking through a much


00:30:23.039 --> 00:30:24.789
greater extent of atmosphere, which


00:30:24.799 --> 00:30:26.710
makes the stars appear dimmer and and


00:30:26.720 --> 00:30:28.789
you get twinkling effects and the


00:30:28.799 --> 00:30:31.029
pollution and dust and whatever in the


00:30:31.039 --> 00:30:33.350
air. So, when you can see things up nice


00:30:33.360 --> 00:30:35.590
high, nice up nice and high, that's a


00:30:35.600 --> 00:30:37.190
whole lot better. So, our friends north


00:30:37.200 --> 00:30:38.789
of the equator can certainly see


00:30:38.799 --> 00:30:40.710
Sagittarius and Scorpius as well, but


00:30:40.720 --> 00:30:42.470
for them, it's lower down towards


00:30:42.480 --> 00:30:43.990
they're lower down towards the horizon.


00:30:44.000 --> 00:30:45.909
and it's still good, but nothing like


00:30:45.919 --> 00:30:47.830
being right underneath these particular


00:30:47.840 --> 00:30:49.269
constellations. Now, turning to the


00:30:49.279 --> 00:30:51.350
planets, Jupiter, it's big and bright.


00:30:51.360 --> 00:30:53.830
It's low down near the northwestern


00:30:53.840 --> 00:30:56.630
horizon after sunset. That's as we view


00:30:56.640 --> 00:30:58.149
it from the southern hemisphere during


00:30:58.159 --> 00:31:00.149
May. Now, make sure you take the


00:31:00.159 --> 00:31:02.549
opportunity to see it in the first two


00:31:02.559 --> 00:31:04.149
or three weeks of May because by the end


00:31:04.159 --> 00:31:05.669
of the month, it'll have disappeared


00:31:05.679 --> 00:31:07.909
into the twilight glow down on the


00:31:07.919 --> 00:31:09.669
northwestern horizon there. It's getting


00:31:09.679 --> 00:31:12.310
lower each night. Mars is quite easy to


00:31:12.320 --> 00:31:14.149
see in the northern half of the sky for


00:31:14.159 --> 00:31:15.510
us here in the south or southern half of


00:31:15.520 --> 00:31:17.510
the sky for our friends in the north.


00:31:17.520 --> 00:31:19.269
It's about halfway up from the horizon.


00:31:19.279 --> 00:31:21.990
It's in a fairly bare patch of sky, so


00:31:22.000 --> 00:31:24.549
it's intense ruddy color does make it


00:31:24.559 --> 00:31:26.389
stand out quite easily amongst all the


00:31:26.399 --> 00:31:28.070
stars that are around it. Now, the other


00:31:28.080 --> 00:31:29.669
three bright planets are all morning


00:31:29.679 --> 00:31:31.510
objects at the moment. It's visible out


00:31:31.520 --> 00:31:34.230
to the east before dawn. First up, we


00:31:34.240 --> 00:31:37.669
have Venus. It's extremely bright at the


00:31:37.679 --> 00:31:39.669
moment. You simply cannot miss it or


00:31:39.679 --> 00:31:41.509
mistake it for anything else. Just if


00:31:41.519 --> 00:31:42.950
you're up before dawn, look to the east,


00:31:42.960 --> 00:31:44.470
which is the direction that the sun


00:31:44.480 --> 00:31:46.630
comes up. And before the sun comes up,


00:31:46.640 --> 00:31:48.549
you see this big bright star looking


00:31:48.559 --> 00:31:50.470
thing in the sky. Well, that's Venus.


00:31:50.480 --> 00:31:52.789
That's uh there's nothing else like it.


00:31:52.799 --> 00:31:55.110
Not far from Venus, but quite a bit


00:31:55.120 --> 00:31:57.110
dimmer is another bright thing that


00:31:57.120 --> 00:31:58.590
looks like a star, but it's actually


00:31:58.600 --> 00:32:01.509
Saturn. And Saturn's fairly easy to spot


00:32:01.519 --> 00:32:03.350
because it's, you know, compared to


00:32:03.360 --> 00:32:05.110
other stars or compared to stars, it's


00:32:05.120 --> 00:32:06.710
reasonably bright. It's not bright


00:32:06.720 --> 00:32:08.389
compared to Venus, but it's bright


00:32:08.399 --> 00:32:10.149
enough. And it does have a yellowish


00:32:10.159 --> 00:32:12.870
sort of color to it. Uh about halfway in


00:32:12.880 --> 00:32:14.950
brightness between Saturn and Venus is


00:32:14.960 --> 00:32:16.710
Mercury. The planet Mercury, which is


00:32:16.720 --> 00:32:18.310
the innermost planet. Now, if you want


00:32:18.320 --> 00:32:20.310
to see Mercury, uh yes, you got you got


00:32:20.320 --> 00:32:22.149
to be up before dawn, but you also got


00:32:22.159 --> 00:32:24.630
to get out there and do it now because


00:32:24.640 --> 00:32:26.789
as the month goes on, you'll see Venus


00:32:26.799 --> 00:32:29.430
and Saturn still up fairly high, moving


00:32:29.440 --> 00:32:30.870
further apart from each other, but


00:32:30.880 --> 00:32:32.310
Mercury is going to start dropping down


00:32:32.320 --> 00:32:34.070
toward the horizon for night after


00:32:34.080 --> 00:32:35.909
night. By the end of the third week of


00:32:35.919 --> 00:32:39.190
May, it'll be lost in the glare of the


00:32:39.200 --> 00:32:42.470
uh dawn glory just before sunrise. So


00:32:42.480 --> 00:32:43.909
yeah, if you want to spot Mercury, if


00:32:43.919 --> 00:32:45.430
you've never seen it before, got to be


00:32:45.440 --> 00:32:47.350
up before dawn and got to do it in the


00:32:47.360 --> 00:32:49.029
next few weeks. And let's do Stewart is


00:32:49.039 --> 00:32:50.950
the sky formation. That's science writer


00:32:50.960 --> 00:32:54.980
Jonathan Nelly and this is Spaceime.


00:32:54.990 --> 00:33:08.870
[Music]


00:33:08.880 --> 00:33:11.669
And that's the show for now. Spacetime


00:33:11.679 --> 00:33:13.430
is available every Monday, Wednesday,


00:33:13.440 --> 00:33:15.789
and Friday through bites.com,


00:33:15.799 --> 00:33:18.070
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00:33:18.080 --> 00:33:20.230
podcast download provider, and from


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spacetime withstartgary.com.


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Spacetime's also broadcast through the


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National Science Foundation on Science


00:33:26.880 --> 00:33:29.669
Own Radio and on both iHeart Radio and


00:33:29.679 --> 00:33:31.990
TuneIn Radio. And you can help to


00:33:32.000 --> 00:33:33.669
support our show by visiting the


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Spacetime store for a range of


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promotional merchandising goodies, or by


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becoming a Spacetime patron, which gives


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you access to triple episode commercial


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free versions of the show, as well as


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lots of bonus audio content, which


00:33:45.919 --> 00:33:47.750
doesn't go to air, access to our


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exclusive Facebook group, and other


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rewards. Just go to


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spaceimewithstugarry.com for full


00:33:54.000 --> 00:33:56.389
details. You've been listening to


00:33:56.399 --> 00:33:58.870
Spacetime with Stuart Garry. This has


00:33:58.880 --> 00:34:01.029
been another quality podcast production


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from byes.com.