Lost Galaxy in the Milky Way: Unveiling the Stellar Remnants of Loki

WEBVTT

0
00:00:00.320 --> 00:00:03.200
Stuart Gary: This is space Time Series 29, episode 118

1
00:00:03.360 --> 00:00:05.652
for broadcast on 2nd October

2
00:00:05.788 --> 00:00:08.640
2026. Coming up on Space,

3
00:00:08.960 --> 00:00:11.240
a, uh, lost galaxy hiding deep inside the

4
00:00:11.240 --> 00:00:14.040
Milky Way. NASA to launch a new far

5
00:00:14.040 --> 00:00:16.480
infrared Space Telescope and

6
00:00:16.480 --> 00:00:19.400
discovery of a huge new crater on the surface

7
00:00:19.400 --> 00:00:22.400
of the Moon. All that and more coming up

8
00:00:22.640 --> 00:00:23.840
on Space Time.

9
00:00:25.120 --> 00:00:27.920
Welcome to Space Time with Stuart

10
00:00:27.920 --> 00:00:28.240
G.

11
00:00:44.620 --> 00:00:46.660
Astronomers have discovered a group of 20

12
00:00:46.660 --> 00:00:49.020
stars deep inside the Milky Way which may

13
00:00:49.020 --> 00:00:51.260
once have been part of a different galaxy.

14
00:00:51.660 --> 00:00:54.060
The findings, reported in the Monthly Notices

15
00:00:54.060 --> 00:00:56.380
of the Royal Astronomical Society, show how

16
00:00:56.380 --> 00:00:58.740
galaxies like our Milky Way grow and evolve

17
00:00:58.740 --> 00:01:00.860
by merging with or cannibalising other

18
00:01:00.860 --> 00:01:03.790
galaxies. Astronomers are able to

19
00:01:03.790 --> 00:01:05.590
identify the stellar remnants of other

20
00:01:05.590 --> 00:01:07.630
galaxies within the Milky Way because of

21
00:01:07.630 --> 00:01:09.830
their proper motion through space, that is

22
00:01:09.830 --> 00:01:12.310
the eccentricities of their galactic orbits

23
00:01:12.470 --> 00:01:14.750
or by their chemical composition, both of

24
00:01:14.750 --> 00:01:16.590
which are often very different from home

25
00:01:16.590 --> 00:01:19.390
grown stars in the Milky Way. This newly

26
00:01:19.390 --> 00:01:21.550
identified group of stars thought to have

27
00:01:21.550 --> 00:01:23.830
originally formed together in a dwarf galaxy

28
00:01:23.830 --> 00:01:26.070
which the authors have now named Loki, which

29
00:01:26.070 --> 00:01:27.990
must have merged with the Milky Way during

30
00:01:27.990 --> 00:01:30.970
its early evolution. These 20 stars are

31
00:01:30.970 --> 00:01:33.610
all metal poor, I.e. they contain fewer heavy

32
00:01:33.610 --> 00:01:35.810
elements compared to most Milky Way stars.

33
00:01:36.050 --> 00:01:38.050
But they're also very distinct from other low

34
00:01:38.050 --> 00:01:40.130
metallicity stars found further out in the

35
00:01:40.130 --> 00:01:43.130
halo of the Milky Way. Astronomers

36
00:01:43.130 --> 00:01:45.330
refer to all elements other than hydrogen and

37
00:01:45.330 --> 00:01:47.850
helium as metals. The earliest stars in the

38
00:01:47.850 --> 00:01:49.890
universe were made up almost exclusively of

39
00:01:49.890 --> 00:01:51.850
hydrogen and helium, because that's all there

40
00:01:51.850 --> 00:01:54.330
was. Following the Big Bang 13.8 billion

41
00:01:54.330 --> 00:01:57.230
years ago. Virtually all the other elements

42
00:01:57.230 --> 00:01:59.510
that make up today's periodic table were

43
00:01:59.510 --> 00:02:02.070
first created out of these first stars,

44
00:02:02.070 --> 00:02:04.870
either during their lives or when they died.

45
00:02:05.510 --> 00:02:07.870
And as more and more generations of stars

46
00:02:07.870 --> 00:02:10.110
were born, they were able to fuse heavier and

47
00:02:10.110 --> 00:02:13.070
heavier elements together. So by determining

48
00:02:13.070 --> 00:02:15.230
the metallicity of a star, astronomers can

49
00:02:15.230 --> 00:02:17.430
determine a star's generational age.

50
00:02:17.990 --> 00:02:19.950
Stars with relatively small amounts of

51
00:02:19.950 --> 00:02:21.910
heavier elements like iron are ah, referred

52
00:02:21.910 --> 00:02:24.290
to as metal pore or low metallicity.

53
00:02:24.610 --> 00:02:26.850
And early galaxies made up of these stars

54
00:02:26.850 --> 00:02:28.450
were the building blocks of the early

55
00:02:28.450 --> 00:02:31.130
universe. Over aeons, these

56
00:02:31.130 --> 00:02:33.090
galactic building blocks merged together,

57
00:02:33.170 --> 00:02:35.530
dispersing their stellar gaseous and dark

58
00:02:35.530 --> 00:02:37.490
matter content into the next generation of

59
00:02:37.490 --> 00:02:40.330
galaxies. Stellar surveys of the

60
00:02:40.330 --> 00:02:42.210
Milky Way have shown that most low

61
00:02:42.210 --> 00:02:44.690
metallicity stars are located in the galactic

62
00:02:44.690 --> 00:02:47.610
halo around the outskirts of the galaxy. But

63
00:02:47.610 --> 00:02:49.490
this new study looked at the chemical

64
00:02:49.490 --> 00:02:52.090
composition of A group of 20 metal pore stars

65
00:02:52.090 --> 00:02:54.370
located far away from the galactic halo in

66
00:02:54.370 --> 00:02:57.070
the disc of the Milky Way. The group

67
00:02:57.070 --> 00:02:59.510
contained both prograde and retrograde

68
00:02:59.510 --> 00:03:02.350
stars, all with fairly high eccentricities.

69
00:03:02.670 --> 00:03:04.630
The star's chemical compositions were

70
00:03:04.630 --> 00:03:06.750
compared to those of halo stars, dwarf

71
00:03:06.750 --> 00:03:09.230
galaxies and computer simulated models.

72
00:03:09.710 --> 00:03:11.470
The authors found that the chemical

73
00:03:11.470 --> 00:03:13.270
signatures in this group of 20 stars

74
00:03:13.270 --> 00:03:15.150
suggested enrichment from high energy

75
00:03:15.230 --> 00:03:17.870
supernovae, from hypernovae, from fast

76
00:03:17.870 --> 00:03:20.470
rotating massive stars, and from neutron star

77
00:03:20.470 --> 00:03:23.290
mergers, but no white dwarf explosions.

78
00:03:23.690 --> 00:03:25.730
And they say this suggests that this group of

79
00:03:25.730 --> 00:03:28.650
stars likely all originated in a short lived

80
00:03:28.650 --> 00:03:31.650
energetic dwarf galaxy. The compositions were

81
00:03:31.650 --> 00:03:33.850
the same for both prograde and retrograde

82
00:03:33.850 --> 00:03:36.210
orbiting stars, again suggesting similar

83
00:03:36.210 --> 00:03:39.010
origins. Overall, the authors say the

84
00:03:39.010 --> 00:03:40.890
results suggest that these stars all came

85
00:03:40.890 --> 00:03:43.090
from a distinct and separate origin compared

86
00:03:43.090 --> 00:03:45.350
to the metal pore stars in the galactic halo.

87
00:03:45.350 --> 00:03:47.450
Uh, this is space time

88
00:03:48.330 --> 00:03:50.490
still to come NASA to launch a new Far

89
00:03:50.490 --> 00:03:53.130
Infrared Space Telescope and discovery of a

90
00:03:53.130 --> 00:03:55.970
new crater on the surface of the Moon. All

91
00:03:55.970 --> 00:03:58.570
that and more still to come on space time,

92
00:04:04.170 --> 00:04:06.530
NASA has announced a new mission to use a Far

93
00:04:06.530 --> 00:04:08.770
Infrared Space Telescope to explore the

94
00:04:08.770 --> 00:04:10.650
history and evolution of the universe.

95
00:04:11.210 --> 00:04:13.330
The Probe Far Infrared Mission for

96
00:04:13.330 --> 00:04:15.810
Astrophysics, or prima, will be the first of

97
00:04:15.810 --> 00:04:18.330
a new class of NASA astrophysics missions

98
00:04:18.330 --> 00:04:21.229
called probe explorers. NASA's Jet

99
00:04:21.229 --> 00:04:23.669
Propulsion Laboratory in Pasadena, California

100
00:04:23.669 --> 00:04:26.649
will manage the $1.2 billion Space Based

101
00:04:26.769 --> 00:04:28.709
Observatory, which is slated for launch in

102
00:04:28.709 --> 00:04:31.309
2033 on UM, an initial five year

103
00:04:31.309 --> 00:04:33.469
mission. The spacecraft will use a

104
00:04:33.469 --> 00:04:36.109
1.8-metre telescope to undertake deep

105
00:04:36.109 --> 00:04:38.709
surveys of the universe in the far infrared,

106
00:04:38.949 --> 00:04:40.989
helping to bridge the gap between existing

107
00:04:40.989 --> 00:04:43.229
infrared observatories like NASA's Webb Space

108
00:04:43.229 --> 00:04:45.509
Telescope and radio telescopes which operate

109
00:04:45.509 --> 00:04:47.389
at millimetre, submillimeter and radio

110
00:04:47.389 --> 00:04:50.130
wavelengths. By studying radiant energy

111
00:04:50.210 --> 00:04:52.930
that only emerges in the far infrared, PRIMA

112
00:04:52.930 --> 00:04:54.850
will address questions about the universe,

113
00:04:54.850 --> 00:04:57.330
including the origins of planets outside our

114
00:04:57.330 --> 00:04:59.650
solar system, how galaxies and their black

115
00:04:59.650 --> 00:05:01.850
holes have grown and evolved over cosmic

116
00:05:01.850 --> 00:05:04.010
history, and how dust and heavy elements have

117
00:05:04.010 --> 00:05:06.890
built up in the universe across aeons, all

118
00:05:06.890 --> 00:05:09.050
helping to paint a better picture of why the

119
00:05:09.050 --> 00:05:10.770
universe looks the way it does today.

120
00:05:11.650 --> 00:05:14.490
NASA Associate Administrator Nikki Fox says

121
00:05:14.490 --> 00:05:16.810
the PRIMA mission is humanity's next window

122
00:05:16.810 --> 00:05:19.490
into the deep universe, unveiling the obscure

123
00:05:19.490 --> 00:05:22.150
across cosmic time to better understand the

124
00:05:22.150 --> 00:05:24.590
formation of planets, stars, black holes, and

125
00:05:24.590 --> 00:05:27.350
even how water came to Earth. Following

126
00:05:27.350 --> 00:05:29.510
its selection, the PRIMA project will now

127
00:05:29.510 --> 00:05:31.830
move into Phase B, which will advance the

128
00:05:31.830 --> 00:05:33.750
preliminary design and technology for the

129
00:05:33.750 --> 00:05:36.069
development of the mission. And needless to

130
00:05:36.069 --> 00:05:38.830
say, we'll keep you informed. This

131
00:05:38.830 --> 00:05:41.630
is space time still to come.

132
00:05:41.710 --> 00:05:44.510
NASA discovers a huge new crater on the Moon

133
00:05:44.510 --> 00:05:47.270
and the Alpha Centauri star system. The Large

134
00:05:47.270 --> 00:05:49.950
and Small Magellanic Clouds and no less than

135
00:05:49.950 --> 00:05:52.020
three meteor showers are among the highest

136
00:05:52.090 --> 00:05:54.370
highlights of the October night skies on

137
00:05:54.370 --> 00:05:55.130
Skywatch.

138
00:06:10.090 --> 00:06:11.890
Scientists have discovered a huge new

139
00:06:11.890 --> 00:06:13.770
asteroid impact crater on the moon.

140
00:06:14.250 --> 00:06:17.050
Astronomers say the steep sided, 222

141
00:06:17.050 --> 00:06:20.050
metre wide crater is 43 metres deep and was

142
00:06:20.050 --> 00:06:22.130
made about two years ago, but was initially

143
00:06:22.130 --> 00:06:24.990
unnoticed. The impact also escaped real

144
00:06:24.990 --> 00:06:27.230
time detection by telescopes on Earth and in

145
00:06:27.230 --> 00:06:29.830
space. It was NASA's Lunar Reconnaissance

146
00:06:29.830 --> 00:06:32.110
Orbiter spacecraft which detected the then

147
00:06:32.110 --> 00:06:34.270
newly formed crater on the moon's near side

148
00:06:34.270 --> 00:06:37.190
in May 2024. But scientists

149
00:06:37.190 --> 00:06:39.429
remained unaware of the impact event, so they

150
00:06:39.429 --> 00:06:41.030
got around to studying the data from the

151
00:06:41.030 --> 00:06:42.990
Lunar Reconnaissance Orbiter back in August

152
00:06:42.990 --> 00:06:45.630
last year. They then instructed the orbiter

153
00:06:45.630 --> 00:06:47.590
to gather more images of the impact feature,

154
00:06:47.590 --> 00:06:50.510
resulting in a final confirmation. It appears

155
00:06:50.510 --> 00:06:52.790
the impact event ejected a debris trail on

156
00:06:52.790 --> 00:06:54.870
the lunar surface more than 100 kilometres

157
00:06:54.870 --> 00:06:57.590
long. Mark Robinson, the

158
00:06:57.590 --> 00:06:59.310
chief scientist for the Lunar Reconnaissance

159
00:06:59.310 --> 00:07:01.390
Orbiter's cameras, says dust and rocky

160
00:07:01.390 --> 00:07:03.630
regolith were hurled away at a higher angle

161
00:07:03.630 --> 00:07:06.430
than expected. A separate study identified

162
00:07:06.430 --> 00:07:08.790
a seven kilometre wide cold spot near the new

163
00:07:08.790 --> 00:07:10.670
crater, consistent with the loosening of

164
00:07:10.670 --> 00:07:13.310
lunar regolith from the impact. The crate has

165
00:07:13.310 --> 00:07:15.390
been named after the late Thomas McGretchen,

166
00:07:15.390 --> 00:07:17.150
former director of Houston's Lunar and

167
00:07:17.150 --> 00:07:19.860
Planetary Institute. A report in the journal

168
00:07:19.860 --> 00:07:22.020
Science Advances claims it's the solar

169
00:07:22.020 --> 00:07:24.100
system's biggest known impact crater in

170
00:07:24.100 --> 00:07:26.540
recent times and three times larger than

171
00:07:26.540 --> 00:07:28.140
Lunar Reconnaissance Orbiter's previous

172
00:07:28.140 --> 00:07:30.740
record holder more than a decade ago. The

173
00:07:30.740 --> 00:07:33.180
authors say craters of this size usually only

174
00:07:33.180 --> 00:07:36.180
happen once every 132 years, effectively

175
00:07:36.180 --> 00:07:38.140
a once in a lifetime observation.

176
00:07:38.620 --> 00:07:41.220
Robinson says Lunar Reconnaissance Orbiter's

177
00:07:41.220 --> 00:07:43.340
numerous crater discoveries since its launch

178
00:07:43.340 --> 00:07:46.220
in 2009 showed that the moon's top 2 to 3

179
00:07:46.220 --> 00:07:48.660
centimetres of regolith is being overturned

180
00:07:48.660 --> 00:07:51.400
by ejected material roughly every 80,000

181
00:07:51.560 --> 00:07:53.800
years, which is faster than previously

182
00:07:53.800 --> 00:07:55.960
thought by Moon standards. It's lunar

183
00:07:55.960 --> 00:07:58.800
gardening at high speed, he says NASA's

184
00:07:58.800 --> 00:08:00.480
scientists will now need to calculate the

185
00:08:00.480 --> 00:08:02.880
risk of ejected crater materials striking the

186
00:08:02.880 --> 00:08:05.560
agency's planned moon base. That information

187
00:08:05.560 --> 00:08:07.680
will help engineers hardened structures to

188
00:08:07.680 --> 00:08:10.600
better protect future crew members. This

189
00:08:10.600 --> 00:08:11.640
is space time.

190
00:08:27.700 --> 00:08:29.620
And time now to turn our eyes to the skies

191
00:08:29.620 --> 00:08:31.420
and check out the celestial sphere for

192
00:08:31.420 --> 00:08:34.340
October. On skywatch, October is

193
00:08:34.340 --> 00:08:36.340
the tenth month of the year. And that may

194
00:08:36.340 --> 00:08:39.020
seem confusing since octo Latin Latin means

195
00:08:39.020 --> 00:08:41.900
eight rather than ten. The answer lies

196
00:08:41.900 --> 00:08:44.300
in the old Roman calendar, which had just 10

197
00:08:44.300 --> 00:08:46.580
months before the addition of January and

198
00:08:46.580 --> 00:08:49.390
February. And that 10 month year is still

199
00:08:49.390 --> 00:08:52.150
reflected today, with the name September or

200
00:08:52.150 --> 00:08:55.150
septum being Latin for 7, October or

201
00:08:55.150 --> 00:08:57.830
Octo meaning 8, November or November

202
00:08:57.830 --> 00:09:00.590
9 and December or Deci meaning 10.

203
00:09:01.710 --> 00:09:04.029
Of course, the highlight of October for kids

204
00:09:04.029 --> 00:09:06.110
and those who are young at Heart has to be

205
00:09:06.110 --> 00:09:08.750
the last day of the month celebrated as All

206
00:09:08.750 --> 00:09:10.830
Hallows Evening, or Halloween.

207
00:09:11.470 --> 00:09:14.030
Halloween is based on ancient Celtic pagan

208
00:09:14.030 --> 00:09:16.430
festivals such as Samhain, uh, the Gaelic

209
00:09:16.430 --> 00:09:19.230
festival of the dead. Samhain was eventually

210
00:09:19.230 --> 00:09:21.710
Christianized by the early church to become

211
00:09:21.710 --> 00:09:24.430
All Saints or All Hallows Eve, or simply

212
00:09:24.430 --> 00:09:26.950
Halloween. It's a time when darkness

213
00:09:26.950 --> 00:09:29.590
overtakes the light of day, a reference to

214
00:09:29.590 --> 00:09:31.750
the increasing hours of darkness as the

215
00:09:31.750 --> 00:09:34.030
planet's northern hemisphere moves towards

216
00:09:34.030 --> 00:09:36.910
longer winter nights. And so it's a time

217
00:09:36.910 --> 00:09:39.470
when the harvest comes to an end. The

218
00:09:39.470 --> 00:09:42.230
increased hours of darkness mean the boundary

219
00:09:42.230 --> 00:09:44.110
between the world of the living and the world

220
00:09:44.110 --> 00:09:46.510
of the dead becomes especially thin,

221
00:09:47.060 --> 00:09:49.860
allowing the dead and supernatural to rise

222
00:09:49.860 --> 00:09:52.820
in search of the living. And so the living

223
00:09:52.820 --> 00:09:55.340
wear disguises so as not to be recognised by

224
00:09:55.340 --> 00:09:57.540
the dead. And it's this which has led to

225
00:09:57.540 --> 00:09:59.820
today's tradition of the Halloween fancy

226
00:09:59.820 --> 00:10:02.300
dress party. In some parts of the world,

227
00:10:02.300 --> 00:10:04.860
cross dressing is popular on Halloween, a

228
00:10:04.860 --> 00:10:06.780
reflection of the secret desires and

229
00:10:06.780 --> 00:10:08.900
fantasies of their pagan ancestors,

230
00:10:09.300 --> 00:10:11.780
sometimes not so many generations removed.

231
00:10:12.430 --> 00:10:14.950
To ensure that crops and livestock survived

232
00:10:14.950 --> 00:10:17.150
the cold winter months ahead, offerings of

233
00:10:17.150 --> 00:10:19.350
food and drink would be left outside for the

234
00:10:19.350 --> 00:10:22.030
spirits and fairies of the other side. And it

235
00:10:22.030 --> 00:10:24.230
was this which ultimately led to today's

236
00:10:24.230 --> 00:10:26.670
practice of trick or treat. Also,

237
00:10:26.830 --> 00:10:29.030
candles would be lit and prayers offered to

238
00:10:29.030 --> 00:10:31.270
the souls of the dead, as Halloween was a

239
00:10:31.270 --> 00:10:33.110
time when the spirits of the dead would

240
00:10:33.110 --> 00:10:36.030
return to their former homes. Special

241
00:10:36.110 --> 00:10:38.590
bonfires were also lit on Halloween to light

242
00:10:38.590 --> 00:10:41.030
the darkness, thereby preventing souls of the

243
00:10:41.030 --> 00:10:43.310
dead from returning and keeping the evil

244
00:10:43.310 --> 00:10:46.150
away. The flames, smoke and ashes

245
00:10:46.150 --> 00:10:48.230
were deemed to have protective and cleansing

246
00:10:48.230 --> 00:10:51.150
powers and were used for divination. As

247
00:10:51.150 --> 00:10:53.230
for the tradition of carving pumpkins into

248
00:10:53.230 --> 00:10:55.710
jack o', lanterns, well, that was originally

249
00:10:55.710 --> 00:10:57.870
meant either to represent spirits or

250
00:10:57.870 --> 00:11:00.550
supernatural beings, or alternatively, to

251
00:11:00.550 --> 00:11:01.950
ward off evil spirits.

252
00:11:02.510 --> 00:11:04.750
In many parts of the world, the Christian

253
00:11:04.750 --> 00:11:07.230
religious observances of All Hallows Eve

254
00:11:07.230 --> 00:11:09.390
include attending church services and

255
00:11:09.390 --> 00:11:11.710
lighting candles on the graves of the dead.

256
00:11:12.370 --> 00:11:14.610
And Christians historically abstained from

257
00:11:14.610 --> 00:11:16.720
eating meat on All Hallows Eve. A, uh,

258
00:11:16.810 --> 00:11:18.570
tradition reflected in the eating of certain

259
00:11:18.570 --> 00:11:21.170
vegetable foods on the day, including apples,

260
00:11:21.250 --> 00:11:23.730
potato pancakes and soul cakes.

261
00:11:24.130 --> 00:11:26.530
Apple bobbing originated because the apple

262
00:11:26.530 --> 00:11:29.450
was a Celtic symbol of love, and so grabbing

263
00:11:29.450 --> 00:11:31.930
the apple with your teeth had certain erotic

264
00:11:31.930 --> 00:11:34.890
overtones. Halloween is a time

265
00:11:34.890 --> 00:11:37.250
of fortune telling and divination games,

266
00:11:37.490 --> 00:11:39.970
playing pranks to scare people, visiting

267
00:11:39.970 --> 00:11:42.570
haunted attractions, telling scary stories,

268
00:11:42.810 --> 00:11:44.970
and, of course, watching horror movies.

269
00:11:46.250 --> 00:11:48.490
Looking to the southwest, you'll see the two

270
00:11:48.490 --> 00:11:50.930
bright pointed stars which show the way to

271
00:11:50.930 --> 00:11:53.730
the Southern cross, the brightest and what

272
00:11:53.730 --> 00:11:55.689
also looks like the more distant of the two

273
00:11:55.689 --> 00:11:57.890
stars from the Southern Cross is Alpha

274
00:11:57.890 --> 00:12:00.210
Centauri, which is actually the nearest star

275
00:12:00.210 --> 00:12:03.130
system to our own solar system. Alpha

276
00:12:03.130 --> 00:12:05.690
Centauri is a triple star system comprising

277
00:12:05.690 --> 00:12:08.530
two stars, Alpha Centauri A and B, which

278
00:12:08.530 --> 00:12:10.890
orbit each other in a binary, and a third

279
00:12:10.890 --> 00:12:13.650
star, Proxima Centauri, which orbit the pair

280
00:12:14.290 --> 00:12:16.930
like the Sun, Alpha Centauri E is a spectral

281
00:12:16.930 --> 00:12:19.850
type G yellow dwarf star. It's about

282
00:12:19.850 --> 00:12:22.570
10% more massive than our sun and about one

283
00:12:22.570 --> 00:12:24.130
and a half times as luminous.

284
00:12:24.930 --> 00:12:27.730
Astronomers describe stars in terms of

285
00:12:27.730 --> 00:12:30.410
spectral types. It's a classification

286
00:12:30.410 --> 00:12:32.010
system based on temperature and

287
00:12:32.010 --> 00:12:34.930
characteristics. The hottest, most massive

288
00:12:34.930 --> 00:12:37.610
and most luminous stars are known as spectral

289
00:12:37.610 --> 00:12:40.500
type O blue stars. They are followed

290
00:12:40.500 --> 00:12:43.420
by spectral type B blue white stars. Then

291
00:12:43.420 --> 00:12:46.220
spectral type A white stars, spectral

292
00:12:46.220 --> 00:12:49.020
type F, whitish yellow stars, spectral

293
00:12:49.020 --> 00:12:51.380
type G yellow stars. That's where our sun

294
00:12:51.380 --> 00:12:53.900
fits in. Spectral type K orange

295
00:12:53.900 --> 00:12:54.460
stars.

296
00:12:54.700 --> 00:12:57.300
And the coolest and least massive stars of

297
00:12:57.300 --> 00:13:00.140
all are the spectral type M red stars.

298
00:13:00.540 --> 00:13:02.500
Each spectral classification is also

299
00:13:02.500 --> 00:13:05.020
subdivided using a numeric digit to represent

300
00:13:05.180 --> 00:13:07.380
temperature, with zero being the hottest and

301
00:13:07.380 --> 00:13:09.960
nine the coolest, and a Roman numeral to

302
00:13:09.960 --> 00:13:12.800
represent luminosity. Now, you pull all that

303
00:13:12.800 --> 00:13:15.800
together and our sun becomes a G2V

304
00:13:15.800 --> 00:13:18.320
or G25 yellow dwarf star.

305
00:13:19.040 --> 00:13:21.240
Also included in the stellar classification

306
00:13:21.240 --> 00:13:24.000
system are spectral types LT and Y,

307
00:13:24.080 --> 00:13:26.320
which are assigned to failed stars known as

308
00:13:26.320 --> 00:13:28.720
brown dwarfs, some of which were actually

309
00:13:28.720 --> 00:13:31.440
born as spectral type um M red stars, but

310
00:13:31.440 --> 00:13:33.680
became brown dwarves after losing some of

311
00:13:33.680 --> 00:13:36.650
their mass. Brown dwarfs fit into a unique

312
00:13:36.650 --> 00:13:39.010
category between the largest planets, which

313
00:13:39.010 --> 00:13:41.250
can be up to 13 times the Mass of Jupiter,

314
00:13:41.410 --> 00:13:44.210
and the smallest stars, those spectral

315
00:13:44.210 --> 00:13:46.690
type M red dwarf stars we mentioned earlier.

316
00:13:47.330 --> 00:13:50.010
These can be 75 to 80 times the mass of

317
00:13:50.010 --> 00:13:52.690
Jupiter, or about 0.08

318
00:13:52.690 --> 00:13:55.650
solar masses. Alpha Centauri

319
00:13:55.650 --> 00:13:58.650
A's binary partner, Alpha Centauri B, is

320
00:13:58.650 --> 00:14:01.590
a special type K orange dwarf star, a

321
00:14:01.590 --> 00:14:03.990
little smaller and cooler than its companion,

322
00:14:03.990 --> 00:14:06.990
with about 90% of the Sun's mass and about

323
00:14:06.990 --> 00:14:09.710
half its luminosity. This binary

324
00:14:09.710 --> 00:14:12.510
pair, Alpha Centauri A and B, orbit each

325
00:14:12.510 --> 00:14:14.470
other at between 11.2 and

326
00:14:14.470 --> 00:14:17.030
35.6 astronomical units.

327
00:14:17.510 --> 00:14:19.990
An astronomical unit is the average distance

328
00:14:19.990 --> 00:14:22.110
between the Earth and the sun, which equates

329
00:14:22.110 --> 00:14:24.990
to about 150 million kilometres, or around

330
00:14:24.990 --> 00:14:27.960
8.3 light minutes. So the

331
00:14:27.960 --> 00:14:30.240
pair's orbit around each other varies by

332
00:14:30.240 --> 00:14:32.400
between the average distance between the sun

333
00:14:32.400 --> 00:14:34.960
and Saturn and between the sun and Pluto.

334
00:14:35.360 --> 00:14:38.280
It takes the two stars 79.91

335
00:14:38.280 --> 00:14:41.080
Earth years to complete each orbit. On

336
00:14:41.080 --> 00:14:44.040
average, Alpha Centauri A and b are located

337
00:14:44.040 --> 00:14:46.480
4.37 light years from the Sun.

338
00:14:47.160 --> 00:14:49.240
Uh, although a light year sounds like a

339
00:14:49.240 --> 00:14:51.600
measure of time, it's actually a measure of

340
00:14:51.600 --> 00:14:54.370
distance. A light year is a distance of about

341
00:14:54.370 --> 00:14:57.330
10 trillion kilometres. That's the distance a

342
00:14:57.330 --> 00:14:59.450
photon can travel in a year at the speed of

343
00:14:59.450 --> 00:15:02.170
light, which is around 300,000 kilometres per

344
00:15:02.170 --> 00:15:04.490
second in a vacuum and the ultimate speed

345
00:15:04.490 --> 00:15:05.610
limit of the universe.

346
00:15:06.170 --> 00:15:08.410
The third star in the Alpha Centauri system

347
00:15:08.489 --> 00:15:11.210
is a spectral type M red dwarf star named

348
00:15:11.210 --> 00:15:14.210
Proxima Centauri. Right now, Proxima

349
00:15:14.210 --> 00:15:17.050
Centauri is just 4.25 light years away,

350
00:15:17.130 --> 00:15:19.490
making it the nearest star to the Earth other

351
00:15:19.490 --> 00:15:22.130
than the Sun. It is only loosely

352
00:15:22.130 --> 00:15:24.850
gravitationally bound to Alpha Centauri A and

353
00:15:24.850 --> 00:15:27.370
B, orbiting the pair at an average distance

354
00:15:27.370 --> 00:15:30.210
of 13,000 astronomical units, or

355
00:15:30.210 --> 00:15:32.290
around 0.21 light years.

356
00:15:32.930 --> 00:15:35.409
That's about 430 times the size of

357
00:15:35.409 --> 00:15:37.930
Neptune's 30 astronomical unit orbit around

358
00:15:37.930 --> 00:15:40.050
the sun. In 2016,

359
00:15:40.290 --> 00:15:42.250
astronomers confirmed the existence of an

360
00:15:42.250 --> 00:15:44.490
Earth sized terrestrial planet orbiting

361
00:15:44.490 --> 00:15:46.410
within the habitable zone of Proxima

362
00:15:46.410 --> 00:15:48.930
Centauri, making it the nearest known

363
00:15:48.930 --> 00:15:51.410
extrasolar or exoplanet to Earth.

364
00:15:51.890 --> 00:15:54.130
The habitable zone, which is sometimes also

365
00:15:54.130 --> 00:15:56.370
referred to as the Goldilocks zone, um, is

366
00:15:56.370 --> 00:15:58.970
that area out from a star where it's not too

367
00:15:58.970 --> 00:16:01.730
hot, not too cold, but just right for

368
00:16:01.730 --> 00:16:04.010
liquid water, essential for life as we know

369
00:16:04.010 --> 00:16:07.010
it to exist on the planet's surface. The

370
00:16:07.010 --> 00:16:09.650
planet known as Proxima B takes just 11

371
00:16:09.650 --> 00:16:11.970
Earth days to complete one orbit around its

372
00:16:11.970 --> 00:16:14.610
host star. Uh, that's far closer than

373
00:16:14.610 --> 00:16:17.450
Mercury's 88 Earth Day orbit around the Sun.

374
00:16:18.010 --> 00:16:20.370
A few years ago, a second more distant

375
00:16:20.370 --> 00:16:23.130
planet, Proxima C was also discovered

376
00:16:23.130 --> 00:16:26.010
orbiting around the star, but well outside

377
00:16:26.170 --> 00:16:28.770
its habitable zone. The second and

378
00:16:28.770 --> 00:16:31.410
slightly fainter of the two Pointer stars is

379
00:16:31.410 --> 00:16:34.410
Beta Centauri. And while Alpha Centauri is

380
00:16:34.410 --> 00:16:35.960
the third brightest star in the night, uh,

381
00:16:35.960 --> 00:16:38.490
sky, outshone only by Sirius and

382
00:16:38.490 --> 00:16:41.280
Canopus, Beta Centauri is only about the 10th

383
00:16:41.280 --> 00:16:44.200
brightest. Looking to the southeast

384
00:16:44.200 --> 00:16:46.080
and you'll see the bright blue white star

385
00:16:46.080 --> 00:16:49.000
Alpha Eridni or Achenar, which represents the

386
00:16:49.000 --> 00:16:51.600
southern tip of Eridanus, one of the largest

387
00:16:51.600 --> 00:16:53.640
and longest constellations in the sky.

388
00:16:54.120 --> 00:16:56.960
Achenar is located about 139 light

389
00:16:56.960 --> 00:16:59.760
years away. It's actually a binary

390
00:16:59.760 --> 00:17:02.520
star system comprising two stars, Alpha

391
00:17:02.520 --> 00:17:04.600
Eridani A and Alpha Rhydmi B.

392
00:17:05.310 --> 00:17:07.590
Alpha Riddinier is a height, young, spectral

393
00:17:07.590 --> 00:17:09.950
type B blue star. It has about

394
00:17:09.950 --> 00:17:12.790
6.7 times the mass of the sun and a

395
00:17:12.790 --> 00:17:15.750
stunning 3,150 times the sun's

396
00:17:15.750 --> 00:17:16.590
luminosity.

397
00:17:17.150 --> 00:17:19.910
By comparison, the companion star Alpha Rydni

398
00:17:19.910 --> 00:17:22.670
B appears to be a spectra type A white star

399
00:17:22.670 --> 00:17:25.510
with about twice the Sun's mass. The

400
00:17:25.510 --> 00:17:28.230
two stars orbit each other every 1415

401
00:17:28.230 --> 00:17:30.510
Earth years at an average distance of about

402
00:17:30.510 --> 00:17:33.070
12.3 astronomical units.

403
00:17:33.840 --> 00:17:35.710
Because of its high rotation rate of, uh,

404
00:17:35.710 --> 00:17:38.600
over 16 kilometres per second, Alpha Eridani

405
00:17:38.600 --> 00:17:40.720
A is actually one of the least spherical

406
00:17:40.720 --> 00:17:43.160
stars in the Milky Way. Spinning so

407
00:17:43.160 --> 00:17:45.760
rapidly, it's assumed the shape of an oblique

408
00:17:45.760 --> 00:17:48.000
spheroid with an equatorial diameter

409
00:17:48.000 --> 00:17:50.800
56% greater than its polar diameter.

410
00:17:51.120 --> 00:17:53.680
This distorted shape means the star displays

411
00:17:53.680 --> 00:17:56.120
a significant latitudinal temperature, with

412
00:17:56.120 --> 00:17:58.160
its polar temperature being about 20,000

413
00:17:58.160 --> 00:18:00.360
Kelvin, while its equatorial temperature is

414
00:18:00.360 --> 00:18:02.750
only around 10,000 Kelvin. That's because

415
00:18:02.750 --> 00:18:05.470
it's much further away from its stellar core.

416
00:18:05.950 --> 00:18:07.590
The high polar temperatures, uh, are

417
00:18:07.590 --> 00:18:10.470
generating a fast polar wind that's

418
00:18:10.470 --> 00:18:13.270
ejecting matter from the star and creating a

419
00:18:13.270 --> 00:18:16.030
spectacular polar envelope of hot gas and

420
00:18:16.030 --> 00:18:19.030
plasma. Now, if you look up between the

421
00:18:19.030 --> 00:18:21.470
South Celestial Pole and Achana from a really

422
00:18:21.470 --> 00:18:24.310
dark place, you'll see two faint, fuzzy

423
00:18:24.310 --> 00:18:27.230
looking clouds. Now, these aren't actually

424
00:18:27.310 --> 00:18:30.040
clouds. There are two satellite dwarf

425
00:18:30.040 --> 00:18:32.400
galaxies which orbit the Milky Way. Known as

426
00:18:32.400 --> 00:18:35.000
the Large and Small Magellanic Clouds,

427
00:18:35.320 --> 00:18:37.760
they're named after Ferdinand Magellan, who

428
00:18:37.760 --> 00:18:39.720
became the first European to officially

429
00:18:39.720 --> 00:18:41.760
record them during his expedition to

430
00:18:41.760 --> 00:18:44.760
circumnavigate the Earth between 1519 and

431
00:18:44.760 --> 00:18:47.400
1522. The bigger and

432
00:18:47.400 --> 00:18:49.800
nearer of the pair is the Large Magellanic

433
00:18:49.800 --> 00:18:52.480
Cloud, which is located around 160 light

434
00:18:52.480 --> 00:18:55.170
years away. It's easier to spot about

435
00:18:55.170 --> 00:18:57.650
halfway between Achenar and the Horizon.

436
00:18:58.130 --> 00:19:01.010
It's about 14,000 light years across,

437
00:19:01.730 --> 00:19:03.730
twice that of the Small Magellanic Cloud,

438
00:19:03.730 --> 00:19:06.690
which is located a more distant 200,000 light

439
00:19:06.690 --> 00:19:09.330
years from the Milky Way. Now, by comparison

440
00:19:09.330 --> 00:19:11.650
to these two satellite galaxies, the Milky

441
00:19:11.650 --> 00:19:14.210
Way is huge, 100,000 light years across.

442
00:19:15.010 --> 00:19:17.370
These two dwarf galaxies are separated from

443
00:19:17.370 --> 00:19:20.210
each other by roughly 75,000 light years.

444
00:19:20.940 --> 00:19:22.820
The Magellanic Clouds were considered the

445
00:19:22.820 --> 00:19:25.300
closest galaxies to the Milky way until the

446
00:19:25.300 --> 00:19:28.104
1994 discovery of the Sagittarius Dwarf

447
00:19:28.202 --> 00:19:30.580
Elliptical Galaxy and the 2003

448
00:19:30.580 --> 00:19:32.860
confirmation that the Canis Major dwarf

449
00:19:32.860 --> 00:19:35.340
galaxy is actually our nearest galactic

450
00:19:35.340 --> 00:19:37.860
neighbour. The total mass of the Magellanic

451
00:19:37.860 --> 00:19:40.260
Clouds is uncertain. Only a fraction of their

452
00:19:40.260 --> 00:19:42.380
gas seems to have coalesced into stars. And

453
00:19:42.380 --> 00:19:44.780
they also probably both have very large dark

454
00:19:44.780 --> 00:19:47.750
matter halos. Still, one recent estimate

455
00:19:47.750 --> 00:19:50.030
places the total mass of the Large Magellanic

456
00:19:50.030 --> 00:19:52.470
Cloud at about one tenth that of the Milky

457
00:19:52.470 --> 00:19:54.950
Way. The Magellanic Clouds have both been

458
00:19:54.950 --> 00:19:57.470
greatly distorted by gravitational tidal

459
00:19:57.470 --> 00:20:00.390
interactions as they're gradually torn apart

460
00:20:00.390 --> 00:20:03.350
and absorbed by the Milky Way. These

461
00:20:03.350 --> 00:20:05.950
huge tidal forces have turned both

462
00:20:05.950 --> 00:20:08.790
Magellanic Clouds into irregular, disrupted,

463
00:20:08.790 --> 00:20:11.350
barred spiral galaxies. The Large

464
00:20:11.350 --> 00:20:13.670
Magellanic Cloud still retains a very clear

465
00:20:13.750 --> 00:20:16.470
spiral structure, at least in radio telescope

466
00:20:16.470 --> 00:20:18.930
images of neutral hydrogen. But

467
00:20:18.930 --> 00:20:21.370
gravity isn't a one way street, and the

468
00:20:21.370 --> 00:20:23.210
combined gravitational force of both

469
00:20:23.210 --> 00:20:25.610
Magellanic Clouds is also affecting the Milky

470
00:20:25.610 --> 00:20:27.890
Way, distorting the outer parts of our

471
00:20:27.890 --> 00:20:30.810
galactic disc. And there are streams of

472
00:20:30.810 --> 00:20:33.330
neutral hydrogen gas clouds and isolated

473
00:20:33.330 --> 00:20:36.250
stars connecting both dwarf galaxies to

474
00:20:36.250 --> 00:20:39.170
each other and to the Milky Way. A brilliant

475
00:20:39.170 --> 00:20:41.650
example of galactic cannibalism at work.

476
00:20:42.850 --> 00:20:44.450
Now, if you look just above the Small

477
00:20:44.450 --> 00:20:46.810
Magellanic Cloud, using a backyard telescope

478
00:20:46.810 --> 00:20:49.080
or a good pair of binoculars, you'll see a

479
00:20:49.080 --> 00:20:51.960
small blurry dot that is the

480
00:20:51.960 --> 00:20:54.520
47 Tucanae globular cluster,

481
00:20:54.920 --> 00:20:57.640
a tightly packed ball of stars some 16,000

482
00:20:57.640 --> 00:20:59.800
light years away that were all originally

483
00:20:59.800 --> 00:21:01.600
formed at the same time through the

484
00:21:01.600 --> 00:21:03.760
gravitational collapse of the same molecular

485
00:21:03.760 --> 00:21:06.680
gas and dust cloud. If you look

486
00:21:06.680 --> 00:21:08.640
to the west, you'll see the bright reddish

487
00:21:08.640 --> 00:21:11.560
orange supergiant star Antares, the heart of

488
00:21:11.560 --> 00:21:13.880
the constellation Scorpius the Scorpion.

489
00:21:14.580 --> 00:21:16.340
And above it, you'll see a bunch of stars

490
00:21:16.340 --> 00:21:18.180
stretching out, shaped like a reverse

491
00:21:18.180 --> 00:21:18.980
question mark.

492
00:21:19.220 --> 00:21:20.900
That's the tail of the Scorpion.

493
00:21:22.020 --> 00:21:24.340
Now, just above and to the north is the

494
00:21:24.340 --> 00:21:26.740
constellation Sagittarius the Archer.

495
00:21:27.220 --> 00:21:29.660
Sagittarius shows the way to the supermassive

496
00:21:29.660 --> 00:21:31.580
black hole at the centre of the Milky way

497
00:21:31.580 --> 00:21:34.500
galaxy, some 27,000 light years away.

498
00:21:34.980 --> 00:21:37.540
This monster black hole, known as Sagittarius

499
00:21:37.540 --> 00:21:40.180
a, has about 4.3 million

500
00:21:40.420 --> 00:21:42.020
times the mass of our Sun.

501
00:21:43.370 --> 00:21:45.250
Now, looking to the north northwest this time

502
00:21:45.250 --> 00:21:47.090
of the year, you'll see the constellation

503
00:21:47.090 --> 00:21:49.490
Lyra the Harp and its brightest star,

504
00:21:49.490 --> 00:21:51.690
Vega, the fifth brightest star in the night

505
00:21:51.690 --> 00:21:54.330
sky and one of the closest, at, uh, just 25

506
00:21:54.330 --> 00:21:57.290
light years away. Vega is a special

507
00:21:57.370 --> 00:22:00.330
type, a white star more than twice the size

508
00:22:00.330 --> 00:22:02.810
and some 40 times the mass of our Sun.

509
00:22:03.930 --> 00:22:06.290
Now, just to the right of Lyra and almost

510
00:22:06.290 --> 00:22:08.600
directly north, just above the horizon, is

511
00:22:08.600 --> 00:22:11.360
the constellation of Cygnus the Swan and its

512
00:22:11.360 --> 00:22:13.360
brightest star, Deneb, one of the most

513
00:22:13.360 --> 00:22:16.360
luminous stars in the sky. Deneb is a

514
00:22:16.360 --> 00:22:19.200
massive spectral type, a white supergiant,

515
00:22:19.200 --> 00:22:22.120
some 19 times the mass and over 100 times

516
00:22:22.120 --> 00:22:24.720
the diameter of the Sun. The star is

517
00:22:24.720 --> 00:22:26.920
somewhere between 55,000 and

518
00:22:26.920 --> 00:22:29.680
196,000 times as luminous as the

519
00:22:29.680 --> 00:22:32.360
Sun. The huge range in luminosity

520
00:22:32.360 --> 00:22:34.440
estimate is caused by the difficulty in

521
00:22:34.440 --> 00:22:36.800
determining Deneb's exact distance from us.

522
00:22:37.540 --> 00:22:39.740
Science's best estimates place it somewhere

523
00:22:39.740 --> 00:22:42.460
around 2600 light years away, give or take

524
00:22:42.460 --> 00:22:45.340
212 light years. High

525
00:22:45.340 --> 00:22:47.340
in the northern sky right now is the

526
00:22:47.340 --> 00:22:49.940
constellation Aquila the Eagle and its

527
00:22:49.940 --> 00:22:52.780
brightest star Altair. Altair

528
00:22:52.780 --> 00:22:55.460
is another spectral type, a white star, but

529
00:22:55.460 --> 00:22:58.260
located a lot closer. Just 17 light years

530
00:22:58.260 --> 00:23:01.060
away, it's about 10 times brighter than the

531
00:23:01.060 --> 00:23:03.940
sun with about 1.89 times the sun's

532
00:23:03.940 --> 00:23:06.880
mass. Despite its size, Altair spins

533
00:23:06.880 --> 00:23:09.560
on its axis in just 10 hours compared to our

534
00:23:09.560 --> 00:23:11.560
Sun's 28 Earth Day rotation.

535
00:23:12.760 --> 00:23:15.760
Now these three stars, Altair, Deneb and

536
00:23:15.760 --> 00:23:18.320
Vega form a stellar grouping known as the

537
00:23:18.320 --> 00:23:21.200
Summer Triangle. Now also in

538
00:23:21.200 --> 00:23:23.640
October, there are three meteor showers,

539
00:23:24.040 --> 00:23:26.320
the Draconids, the Taurids and the

540
00:23:26.320 --> 00:23:29.160
Orionids. The Draconids take

541
00:23:29.160 --> 00:23:32.020
place on October 8th. They're so

542
00:23:32.020 --> 00:23:34.340
named because their meteors appear to radiate

543
00:23:34.340 --> 00:23:36.740
out from the constellation Draco the Dragon

544
00:23:36.740 --> 00:23:39.020
and so are, uh, best viewed from the Northern

545
00:23:39.020 --> 00:23:41.700
Hemisphere. They're actually produced as the

546
00:23:41.700 --> 00:23:43.700
Earth's orbit takes it through the debris

547
00:23:43.700 --> 00:23:46.460
trail left behind by the comet 21P

548
00:23:46.620 --> 00:23:49.580
Shir Kobeni Zinna, which takes about 6.6

549
00:23:49.580 --> 00:23:51.780
Earth years to make a single revolution of

550
00:23:51.780 --> 00:23:54.540
the Sun. The Taurids meteor

551
00:23:54.540 --> 00:23:57.020
shower takes place on October 10th, and as

552
00:23:57.020 --> 00:23:58.940
their name suggests, they appear to radiate

553
00:23:58.940 --> 00:24:01.340
out from the constellation Taurus the Bull.

554
00:24:01.820 --> 00:24:03.700
Their meteors are composed of larger than

555
00:24:03.700 --> 00:24:06.100
average pebbles and dust grains and are

556
00:24:06.100 --> 00:24:08.500
thought to be generated by debris left behind

557
00:24:08.500 --> 00:24:11.260
by the Comet 2P Encke. Although

558
00:24:11.260 --> 00:24:13.740
it's thought that both the Taureds and Encke

559
00:24:13.740 --> 00:24:15.740
could be the remains of an earlier comet

560
00:24:15.740 --> 00:24:18.220
which disintegrated over the past 20,000 to

561
00:24:18.220 --> 00:24:21.020
30,000 years, breaking into several pieces

562
00:24:21.100 --> 00:24:23.180
and releasing material both by normal

563
00:24:23.180 --> 00:24:25.740
cometary activity and possibly also by

564
00:24:25.740 --> 00:24:27.860
gravitational tidal interactions with the

565
00:24:27.860 --> 00:24:30.470
Earth and other planets. The Taurids

566
00:24:30.470 --> 00:24:32.710
debris stream is the largest in the inner

567
00:24:32.710 --> 00:24:35.110
solar system, taking the Earth several weeks

568
00:24:35.110 --> 00:24:37.830
to pass through and resulting in an extended

569
00:24:37.830 --> 00:24:39.990
period of meteor activity compared to other

570
00:24:39.990 --> 00:24:42.270
meteor showers, which are usually over in

571
00:24:42.270 --> 00:24:44.750
just a matter of days. Now, due to the

572
00:24:44.750 --> 00:24:46.670
gravitational perturbations of the planets,

573
00:24:46.670 --> 00:24:48.870
especially Jupiter, the Taurids have been

574
00:24:48.870 --> 00:24:51.470
spread out over time, allowing separate

575
00:24:51.470 --> 00:24:53.630
segments labelled the Northern Taurids and

576
00:24:53.630 --> 00:24:55.710
Southern Taurids to be observable at

577
00:24:55.710 --> 00:24:58.480
different times in different hemispheres. The

578
00:24:58.480 --> 00:25:00.200
Southern Taurids are active from around

579
00:25:00.200 --> 00:25:02.680
September 10 to November 20, while the

580
00:25:02.680 --> 00:25:05.200
northern Taurids are active from October 20

581
00:25:05.200 --> 00:25:07.840
to December 10. The third

582
00:25:07.840 --> 00:25:09.920
meteor shower this month is the Orionids,

583
00:25:09.920 --> 00:25:12.920
which peak on October 20th. They're

584
00:25:12.920 --> 00:25:15.160
caused by debris from the comet Hallie, which

585
00:25:15.160 --> 00:25:17.640
also causes the Eta Achorens meteor shower in

586
00:25:17.640 --> 00:25:20.480
May. Comet Hallie takes 76 years

587
00:25:20.480 --> 00:25:23.480
to complete each orbit around the Sun. It'll

588
00:25:23.480 --> 00:25:26.080
next become visible near Earth in 2061.

589
00:25:26.730 --> 00:25:29.170
The Orionids are equally spectacular in both

590
00:25:29.170 --> 00:25:31.450
northern and Southern hemisphere skies, with

591
00:25:31.450 --> 00:25:34.010
up to 20 meteors an hour, uh, radiating out

592
00:25:34.010 --> 00:25:36.850
from the constellation Orion. The best

593
00:25:36.850 --> 00:25:39.090
time to see the Orionids is just after

594
00:25:39.090 --> 00:25:41.290
midnight and right before dusk.

595
00:25:42.010 --> 00:25:43.970
And joining us now for the rest of our tour

596
00:25:43.970 --> 00:25:46.410
of the October night skies is senior science

597
00:25:46.410 --> 00:25:48.290
writer and sky and Telescope magazine

598
00:25:48.290 --> 00:25:49.610
contributor, Jonathan Nally.

599
00:25:49.690 --> 00:25:51.810
Jonathan Nally: Hi, Stuart. Yeah, well, we're still in spring

600
00:25:51.810 --> 00:25:53.450
here in Australia. We're heading towards

601
00:25:53.450 --> 00:25:54.810
summer. I can definitely feel summer coming

602
00:25:54.810 --> 00:25:56.250
along. The days are feeling different. Days

603
00:25:56.250 --> 00:25:57.850
are nice and bright and warm, and the nights

604
00:25:57.850 --> 00:25:59.430
are generally clear for us at this time of

605
00:25:59.430 --> 00:26:01.390
year and not too cold, which is really good

606
00:26:01.390 --> 00:26:02.950
for stargazing. The further we get into

607
00:26:02.950 --> 00:26:05.070
summer, even better weather wise, you know,

608
00:26:05.070 --> 00:26:06.270
because it's warmer and everything. But

609
00:26:06.270 --> 00:26:08.550
because it's summer, the days are longer and

610
00:26:08.550 --> 00:26:10.910
the hours of nighttime are less. So you have

611
00:26:10.910 --> 00:26:12.430
better conditions for stargazing, but you

612
00:26:12.430 --> 00:26:14.549
have fewer hours. So this sort of late

613
00:26:14.549 --> 00:26:16.550
springtime, pretty good for stargazing. So

614
00:26:16.550 --> 00:26:17.790
let's take a look at what we can see in the

615
00:26:17.790 --> 00:26:19.390
south at this time of the year. So really

616
00:26:19.390 --> 00:26:20.790
deep in the south, we've got the famous

617
00:26:20.790 --> 00:26:22.710
Southern Cross, of course, now it's upside

618
00:26:22.710 --> 00:26:24.510
down at the moment and it's low down in the

619
00:26:24.510 --> 00:26:26.390
southwest, so it'll be either right on the

620
00:26:26.390 --> 00:26:28.470
southern horizon for a lot of people or even

621
00:26:28.470 --> 00:26:29.030
below it.

622
00:26:29.030 --> 00:26:31.210
So you can't see it for most populated

623
00:26:31.210 --> 00:26:33.890
southern latitudes, say Sydney or Brisbane in

624
00:26:33.890 --> 00:26:35.530
Australia and other cities around the

625
00:26:35.530 --> 00:26:37.330
Southern hemisphere, similar latitudes. But

626
00:26:37.330 --> 00:26:39.210
if you're as far south as in Australia, at

627
00:26:39.210 --> 00:26:40.890
least Melbourne or Hobart, you should still

628
00:26:40.890 --> 00:26:42.610
be able to see it fairly easily this time of

629
00:26:42.610 --> 00:26:44.570
the year. Now, panning across to the left or

630
00:26:44.570 --> 00:26:47.130
the east, we can find the two Magellanic

631
00:26:47.130 --> 00:26:48.970
Cloud galaxies. Now, these are the two

632
00:26:48.970 --> 00:26:51.650
nearest sizable galaxies outside our Milky

633
00:26:51.650 --> 00:26:53.370
Way, and they're named after the explorer

634
00:26:53.370 --> 00:26:55.730
Magellan, the Magellanic Galaxies. Now, these

635
00:26:55.730 --> 00:26:58.170
just look like two little faint fuzzy clouds.

636
00:26:58.170 --> 00:27:00.490
So you really need dark sky conditions to see

637
00:27:00.490 --> 00:27:02.360
them. If you're in a big city, you can just

638
00:27:02.360 --> 00:27:04.120
forget it. I can't see them where I am with

639
00:27:04.120 --> 00:27:05.640
the unaided eye. You've really got to get

640
00:27:05.640 --> 00:27:08.080
somewhere dark or away from lights and then

641
00:27:08.080 --> 00:27:10.240
let your eyes get adapted to the dark. And so

642
00:27:10.240 --> 00:27:11.920
if you then look down the southeast, you

643
00:27:11.920 --> 00:27:13.360
might be able to see these things. So you've

644
00:27:13.360 --> 00:27:15.480
got the large Cloud, which is lower down and

645
00:27:15.480 --> 00:27:17.080
a fair distance away from it. And higher up,

646
00:27:17.080 --> 00:27:19.160
you've got the Small Magellanic Cloud. And as

647
00:27:19.160 --> 00:27:21.160
I said, these are the. These are two fairly

648
00:27:21.160 --> 00:27:22.720
sizable galaxies. And they're very close to

649
00:27:22.720 --> 00:27:24.400
the Milky Way, which is why we can see them.

650
00:27:24.400 --> 00:27:26.520
Most other galaxies, uh, I'm just thinking,

651
00:27:26.520 --> 00:27:28.640
well, there's water, two or three

652
00:27:29.330 --> 00:27:31.050
maybe you can count on one hand. The other

653
00:27:31.050 --> 00:27:33.370
galaxy you can see with the unaided eye. Um,

654
00:27:33.410 --> 00:27:35.810
the Andromeda Galaxy and a couple of others.

655
00:27:35.810 --> 00:27:37.930
But they just look like little smudges. These

656
00:27:37.930 --> 00:27:40.690
Magellanic Galaxies, they are quite big,

657
00:27:40.850 --> 00:27:42.810
which is. They look like a cloud. They look

658
00:27:42.810 --> 00:27:44.650
like a fairly sizable cloud. So you'll find

659
00:27:44.650 --> 00:27:46.970
them low down in the southeast at this time

660
00:27:46.970 --> 00:27:48.770
of year. In the early evening now, we've got

661
00:27:48.770 --> 00:27:50.650
the Milky Way stretching from north to south

662
00:27:50.650 --> 00:27:52.850
across the western half of the sky after

663
00:27:52.850 --> 00:27:55.250
sunset with the constellation Sagittarius

664
00:27:55.890 --> 00:27:57.770
and the very impressive Scorpius, which

665
00:27:57.770 --> 00:27:59.610
really does look like a scorpion. They're

666
00:27:59.610 --> 00:28:02.330
easily visible high overhead. But as the

667
00:28:02.330 --> 00:28:05.010
night goes on, by midnight, that half of the

668
00:28:05.010 --> 00:28:07.290
Milky Way will have set below the horizon,

669
00:28:07.290 --> 00:28:09.290
the western horizon, as the Earth continues

670
00:28:09.290 --> 00:28:11.650
to turn now overhead. The sky

671
00:28:12.210 --> 00:28:14.210
seems pretty reasonably empty this time of

672
00:28:14.210 --> 00:28:15.930
year. There are some deep constellations up

673
00:28:15.930 --> 00:28:18.650
there, but they don't seem pretty exciting.

674
00:28:18.650 --> 00:28:20.570
They're a bit dull. Um, they don't have a lot

675
00:28:20.570 --> 00:28:22.290
of bright stars and things. If you get a

676
00:28:22.290 --> 00:28:24.160
telescope onto them, backyard telescope, you

677
00:28:24.160 --> 00:28:25.920
can see lots of things within them, but just

678
00:28:25.920 --> 00:28:28.320
to the naked eye. Capricornus, Sculptor,

679
00:28:28.320 --> 00:28:30.600
Aquarius, Cetus and others, um, they look

680
00:28:30.600 --> 00:28:32.920
fairly bland, the northern part of the sky.

681
00:28:33.000 --> 00:28:34.840
Apologies to our northern listeners, Northern

682
00:28:34.840 --> 00:28:36.320
Hemisphere listeners. But down here in the

683
00:28:36.320 --> 00:28:37.920
south, the bits that we can see at this time

684
00:28:37.920 --> 00:28:39.680
of year, it's pretty dull there as well. If

685
00:28:39.680 --> 00:28:41.440
we were much further north of the equator,

686
00:28:41.440 --> 00:28:43.160
there would be plenty of things to see. But

687
00:28:43.160 --> 00:28:45.240
if you like staying up late or getting up

688
00:28:45.240 --> 00:28:47.720
really early, the skies after midnight in

689
00:28:47.720 --> 00:28:49.720
October are really great. Because the other

690
00:28:49.720 --> 00:28:51.600
half of the Milky Way is rising in the east,

691
00:28:51.600 --> 00:28:53.800
bringing with it the fabulous constellations

692
00:28:53.800 --> 00:28:56.500
of Orion and Taurus and Gemini and Canis

693
00:28:56.500 --> 00:28:58.820
Major and Papus and other ones. To me, these

694
00:28:58.820 --> 00:29:01.260
are the constellations of, um, summer. For

695
00:29:01.260 --> 00:29:02.420
people in the Northern Hemisphere, they're

696
00:29:02.420 --> 00:29:04.100
the constellations of winter. So at the

697
00:29:04.100 --> 00:29:06.180
moment, you've got to be up before dawn to

698
00:29:06.180 --> 00:29:06.580
see them.

699
00:29:06.660 --> 00:29:08.820
But as the weeks go on, they'll be rising

700
00:29:08.820 --> 00:29:10.700
earlier and earlier and earlier. So by the

701
00:29:10.700 --> 00:29:12.140
time summer comes around, they'll be up

702
00:29:12.140 --> 00:29:14.900
invisible in the night sky just after sunset

703
00:29:14.900 --> 00:29:16.980
when the sky gets dark. So this, for me, is a

704
00:29:16.980 --> 00:29:19.500
sign that better weather is coming and better

705
00:29:19.500 --> 00:29:21.540
skies are coming. Lots of great stuff to see.

706
00:29:21.620 --> 00:29:23.860
And all of those constellations here have

707
00:29:23.860 --> 00:29:25.620
plenty of deep sky objects, what astronomers

708
00:29:25.620 --> 00:29:28.040
call deep sky objects you need telescopes

709
00:29:28.040 --> 00:29:30.160
for. But even a small backyard telescope, you

710
00:29:30.160 --> 00:29:32.040
can see star clusters and nebulae and all

711
00:29:32.040 --> 00:29:33.560
sorts of wonderful stuff. So, for instance,

712
00:29:33.560 --> 00:29:35.240
you've got the constellation Canis Major. It

713
00:29:35.240 --> 00:29:36.800
has the brightest star in the night sky,

714
00:29:36.800 --> 00:29:39.160
Sirius, Orion. Uh, it has the two bright

715
00:29:39.160 --> 00:29:41.320
stars, Rigel and Betelgeuse, but it also has

716
00:29:41.320 --> 00:29:43.280
the famous Orion Nebula. Now, the Orion

717
00:29:43.280 --> 00:29:45.760
Nebula is very famous in astronomy circles.

718
00:29:45.760 --> 00:29:47.160
Everyone's probably seen a picture of the

719
00:29:47.160 --> 00:29:47.960
Orion Nebula.

720
00:29:47.960 --> 00:29:49.800
Stuart Gary: Yeah, it's the one I always look for when I

721
00:29:49.800 --> 00:29:52.000
want to work out where the stars are in the

722
00:29:52.000 --> 00:29:53.640
sky. Either that or the Southern Cross.

723
00:29:53.640 --> 00:29:54.880
They're the first ones I go to.

724
00:29:54.880 --> 00:29:57.080
Jonathan Nally: Yeah, because Orion, it's, uh, got the very

725
00:29:57.080 --> 00:29:59.180
distinctive three stars in a row. And it's

726
00:29:59.180 --> 00:30:00.500
got those two other bright stars I mentioned

727
00:30:00.500 --> 00:30:02.660
right here on Betelgeuse. So it is very, very

728
00:30:02.660 --> 00:30:04.260
easy to spot. And it's right on the celestial

729
00:30:04.260 --> 00:30:06.340
equator too. So once you see it, you know,

730
00:30:06.340 --> 00:30:08.580
you know what your orientation is. With the

731
00:30:08.580 --> 00:30:10.700
Orion Nebula, the pictures you see in

732
00:30:10.780 --> 00:30:12.820
magazines and books and on the Internet and

733
00:30:12.820 --> 00:30:14.420
everything, they're taken by electronic

734
00:30:14.420 --> 00:30:16.060
cameras these days that can bring out

735
00:30:16.060 --> 00:30:17.840
fantastic colour and fantastic detail. Uh,

736
00:30:17.840 --> 00:30:19.740
you don't get that with the naked eye. You

737
00:30:19.740 --> 00:30:21.220
don't get that looking through a telescope

738
00:30:21.220 --> 00:30:22.780
either, unless you've got a Whopper

739
00:30:22.780 --> 00:30:24.500
telescope, which most people don't. These

740
00:30:24.500 --> 00:30:25.900
things just generally look like a bit of a

741
00:30:25.900 --> 00:30:28.150
smudge of light. So. But you can see this

742
00:30:28.150 --> 00:30:30.110
Orion Nebula as a smudge of light just with

743
00:30:30.110 --> 00:30:31.950
the unaided eye, if you've got dark enough

744
00:30:31.950 --> 00:30:33.510
sky conditions. And when you look up, you

745
00:30:33.510 --> 00:30:35.270
think, well, that's actually Orion Nebula and

746
00:30:35.270 --> 00:30:36.790
that's that thing. I've seen a big picture in

747
00:30:36.790 --> 00:30:39.150
a book that is amazing. But it's about 1500

748
00:30:39.150 --> 00:30:40.750
light years or so away, a little bit less.

749
00:30:41.470 --> 00:30:43.510
It's quite amazing. And it's a massive star

750
00:30:43.510 --> 00:30:46.350
cloud where new solar systems are being born.

751
00:30:46.510 --> 00:30:48.190
So it's wonderful when you look up and see

752
00:30:48.190 --> 00:30:50.390
something and you realise what you're seeing.

753
00:30:50.390 --> 00:30:52.230
Even if it might not look impressive, it's

754
00:30:52.230 --> 00:30:54.300
impressive because you can see it makes any

755
00:30:54.300 --> 00:30:55.940
sense. And of course, getting a pair of

756
00:30:55.940 --> 00:30:57.660
binoculars or a telescope under the Orion

757
00:30:57.660 --> 00:30:59.580
Nebula makes it look a whole lot better. Now,

758
00:30:59.580 --> 00:31:01.900
above the northeastern, uh, horizon that time

759
00:31:01.900 --> 00:31:03.380
in the morning again, we've got Taurus

760
00:31:03.460 --> 00:31:05.300
constellation. Taurus. And it's got these

761
00:31:05.300 --> 00:31:07.140
star clusters known as the Hyades and the

762
00:31:07.140 --> 00:31:08.980
Pleiades. We talk about the Pleiades all the

763
00:31:08.980 --> 00:31:10.500
time. It's the Seven Sisters. They look

764
00:31:10.500 --> 00:31:12.340
fantastic through binoculars. Just a pair of

765
00:31:12.340 --> 00:31:13.900
binoculars. You don't need a telescope. Just

766
00:31:13.900 --> 00:31:15.380
get some binoculars onto them and they'll

767
00:31:15.380 --> 00:31:16.980
become a lot easier to see. Uh, over the next

768
00:31:16.980 --> 00:31:18.540
couple of months, as I described, they start

769
00:31:18.540 --> 00:31:20.220
to rise higher and then get into the evening

770
00:31:20.220 --> 00:31:22.380
sty rather than the Morning star. Now let's

771
00:31:22.380 --> 00:31:23.940
turn to the planets. There are three of them

772
00:31:23.940 --> 00:31:25.820
on show just after sunset. So if you take a

773
00:31:25.820 --> 00:31:27.460
look to the west, you'll see Mercury and

774
00:31:27.460 --> 00:31:30.100
Venus. Mercury is the smaller, dimmer of the

775
00:31:30.100 --> 00:31:32.500
two lower down in the sky. Venus is the big

776
00:31:32.500 --> 00:31:34.660
bright one higher up. Now, as the days go by,

777
00:31:34.660 --> 00:31:36.620
in the first week and a half, couple of weeks

778
00:31:36.620 --> 00:31:38.620
of October, you'll see Venus will be dropping

779
00:31:38.620 --> 00:31:40.340
down lower each night down towards the

780
00:31:40.340 --> 00:31:42.140
horizon, while Mercury is actually rising

781
00:31:42.140 --> 00:31:44.100
higher up. And they'll pass each other on the

782
00:31:44.100 --> 00:31:45.980
8th, on the evening of the 8th, so they'll be

783
00:31:45.980 --> 00:31:48.140
roughly the same distance above the horizon,

784
00:31:48.140 --> 00:31:49.980
sort of next to each other. Then a few days

785
00:31:49.980 --> 00:31:52.020
later, on the 12th, the moon will make an

786
00:31:52.020 --> 00:31:53.420
appearance. It'll be joining in because the

787
00:31:53.420 --> 00:31:55.340
Moon travels through the sky night after

788
00:31:55.340 --> 00:31:57.260
night, sort of moves along night after night.

789
00:31:57.260 --> 00:31:59.940
So it eventually, um, sidles up to these two

790
00:31:59.940 --> 00:32:02.540
planets on the 12th, making a close triangle

791
00:32:02.540 --> 00:32:04.020
with them. That should be really nice to see.

792
00:32:04.020 --> 00:32:05.140
I'm going to get out and have a look at that

793
00:32:05.140 --> 00:32:06.620
one on the other side of the sky in the

794
00:32:06.620 --> 00:32:08.900
evening we've got Saturn, which is low above

795
00:32:08.900 --> 00:32:09.780
the eastern horizon.

796
00:32:09.780 --> 00:32:11.860
After sunset, give it an hour or two to rise

797
00:32:11.860 --> 00:32:14.020
up out of any murk or obstacles that might be

798
00:32:14.020 --> 00:32:15.740
on your horizon and then have a look. It's

799
00:32:15.740 --> 00:32:17.180
always best to have a look at planets when

800
00:32:17.180 --> 00:32:19.340
they're as high as they can get in the night

801
00:32:19.340 --> 00:32:21.920
sky. Saturn just looks like a, uh, fairly

802
00:32:21.920 --> 00:32:24.240
bright yellowish star to the unaided eye. But

803
00:32:24.240 --> 00:32:26.200
you get a small telescope onto it and you'll

804
00:32:26.200 --> 00:32:28.400
see that it's this giant ringed planet with

805
00:32:28.400 --> 00:32:30.440
these amazing rings going around it. Although

806
00:32:30.440 --> 00:32:32.280
at the moment they are a bit edge on towards

807
00:32:32.280 --> 00:32:34.320
us, so they don't look as great as they do at

808
00:32:34.320 --> 00:32:35.760
other times when the rings are sort of more

809
00:32:35.760 --> 00:32:37.360
angled towards us. But Saturn always

810
00:32:37.360 --> 00:32:38.840
impresses everyone when they see it through a

811
00:32:38.840 --> 00:32:40.920
telescope. It's impressive the first time and

812
00:32:40.920 --> 00:32:42.720
it's impressive every time after that. It's

813
00:32:42.720 --> 00:32:44.600
really, it's one of those things, if you show

814
00:32:44.600 --> 00:32:46.320
someone Saturn through a telescope for the

815
00:32:46.320 --> 00:32:48.440
first time, they'll gasp. They go like that.

816
00:32:48.440 --> 00:32:50.840
It's involuntary. People say that is really

817
00:32:50.840 --> 00:32:52.340
Saturn. It looks like what it looks like in

818
00:32:52.340 --> 00:32:54.180
the pictures. Not often you can get that sort

819
00:32:54.180 --> 00:32:55.380
of thing, um, when you look through a

820
00:32:55.380 --> 00:32:57.140
telescope for the other two bright planets,

821
00:32:57.140 --> 00:32:58.980
Jupiter and Mars, again, you're going to have

822
00:32:58.980 --> 00:33:00.780
to be up very late, a night owl, or you're

823
00:33:00.780 --> 00:33:02.180
going to have to wake up early before dawn

824
00:33:02.180 --> 00:33:04.060
because they both rise over the northeastern

825
00:33:04.060 --> 00:33:05.780
horizon a bit after 4 o' clock in the

826
00:33:05.780 --> 00:33:07.819
morning, just as with Saturn. Give these two

827
00:33:07.819 --> 00:33:09.540
planets an hour or so to rise up out of the

828
00:33:09.540 --> 00:33:11.460
murk down into the horizon and you get a

829
00:33:11.460 --> 00:33:13.140
better view. But don't leave it too long, of

830
00:33:13.140 --> 00:33:14.580
course, because dawn will be just around the

831
00:33:14.580 --> 00:33:17.300
corner. Mars doesn't look like much through a

832
00:33:17.300 --> 00:33:19.260
telescope. It's a fairly small planet a long

833
00:33:19.260 --> 00:33:21.580
way away. Um, you can see that it's a planet.

834
00:33:21.580 --> 00:33:23.020
Doesn't look like a star. You can actually

835
00:33:23.020 --> 00:33:24.960
see that it's a disc of a planet, but it's

836
00:33:24.960 --> 00:33:27.600
pretty small. Jupiter on the other hand, is

837
00:33:27.600 --> 00:33:29.240
very, very impressive, really impressive.

838
00:33:29.240 --> 00:33:30.640
Through a telescope you should be able to

839
00:33:30.640 --> 00:33:33.400
make out some sort of band structure in its

840
00:33:33.400 --> 00:33:35.400
clouds, its cloud system. We can't see any

841
00:33:35.400 --> 00:33:37.360
surface, we just see the clouds. Uh, and it's

842
00:33:37.360 --> 00:33:39.799
got these sort of equatorial bands and sort

843
00:33:39.799 --> 00:33:42.160
of middle bands towards the poles. So it's

844
00:33:42.160 --> 00:33:44.240
got a structured sort of cloud system. You

845
00:33:44.240 --> 00:33:45.800
also should be able to make out several of

846
00:33:45.800 --> 00:33:48.040
its largest moons. They just look like tiny

847
00:33:48.040 --> 00:33:49.840
bright pinpricks of light. There are four of

848
00:33:49.840 --> 00:33:51.360
them that are, ah, fairly easy to see. You

849
00:33:51.360 --> 00:33:53.060
can even see them with binoculars. They don't

850
00:33:53.060 --> 00:33:54.540
look like pictures you would see of the moon,

851
00:33:54.540 --> 00:33:56.340
they just look like tiny pinpricks of light.

852
00:33:56.340 --> 00:33:58.180
But if you go out night after night and have

853
00:33:58.180 --> 00:33:59.780
a look, you'll see that they've moved as they

854
00:33:59.780 --> 00:34:01.460
go around the planet very quickly. And

855
00:34:01.460 --> 00:34:03.180
sometimes you might see two on one side and

856
00:34:03.180 --> 00:34:05.380
two on the other side. Some might see three

857
00:34:05.380 --> 00:34:06.980
on one side and one on the other side.

858
00:34:06.980 --> 00:34:08.580
Sometimes you might only see two or three.

859
00:34:08.580 --> 00:34:09.940
You think, where are the other ones gone?

860
00:34:09.940 --> 00:34:11.940
Well, they're probably around behind Jupiter

861
00:34:11.940 --> 00:34:13.660
or they could be in Jupiter's shadow if

862
00:34:13.660 --> 00:34:15.540
they're not directly behind. So that's really

863
00:34:15.540 --> 00:34:17.780
fascinating to see if you want to see what

864
00:34:17.780 --> 00:34:20.180
Galileo saw, which is what helped start off

865
00:34:20.180 --> 00:34:21.140
scientific revolution.

866
00:34:21.140 --> 00:34:23.380
Stuart Gary: Yeah, but looking at Jupiter got Galileo in a

867
00:34:23.380 --> 00:34:24.159
lot of trouble.

868
00:34:25.119 --> 00:34:26.599
Jonathan Nally: Well, you won't get into trouble these days.

869
00:34:26.599 --> 00:34:27.919
You won't be put under house arrest or

870
00:34:27.919 --> 00:34:29.119
anything. If you go out and have a look at

871
00:34:29.119 --> 00:34:31.319
Jupiter, See, back in his days before the

872
00:34:31.319 --> 00:34:32.999
telescope was around, when people looked up,

873
00:34:32.999 --> 00:34:34.759
they could just see that there were the stars

874
00:34:34.759 --> 00:34:36.959
which never changed position. And there are

875
00:34:36.959 --> 00:34:39.039
these planets, planets from the Greek word

876
00:34:39.039 --> 00:34:41.199
meaning wanderers, that, um, move along the

877
00:34:41.199 --> 00:34:43.719
night sky in predictable paths. And people

878
00:34:43.719 --> 00:34:45.359
have known about them for thousands of years.

879
00:34:45.359 --> 00:34:47.239
And that was it. That's all we knew about the

880
00:34:47.239 --> 00:34:47.879
night sky.

881
00:34:47.879 --> 00:34:49.119
And of course there were all these

882
00:34:49.199 --> 00:34:51.630
mythological things about, you know, that the

883
00:34:51.710 --> 00:34:54.190
heavens being perfect, you know, unchanging

884
00:34:54.190 --> 00:34:56.830
perfect, and, uh, it was all God's plan sort

885
00:34:56.830 --> 00:34:58.590
of thing. And, and the Earth was in the

886
00:34:58.590 --> 00:35:00.270
centre of the universe and Earth was special

887
00:35:00.270 --> 00:35:01.870
and everything was supposed to go around the

888
00:35:01.870 --> 00:35:03.270
Earth, which we now of course know is not

889
00:35:03.270 --> 00:35:05.430
right. But when Galileo look at Jupiter and

890
00:35:05.430 --> 00:35:07.230
he saw these little moons and night after

891
00:35:07.230 --> 00:35:08.950
night he saw that their position changed, he

892
00:35:08.950 --> 00:35:10.910
thought, aha, uh-huh, they must be moon,

893
00:35:10.990 --> 00:35:12.670
that's a planet and it must have its own

894
00:35:12.670 --> 00:35:14.950
moons going around it. So things aren't as

895
00:35:14.950 --> 00:35:17.310
perfect as we thought they were. There are

896
00:35:17.310 --> 00:35:19.750
other places out there that seem to be like

897
00:35:19.750 --> 00:35:21.950
Earth and that sort of kicked off, kicked off

898
00:35:21.950 --> 00:35:23.530
the whole scientific revolution and aren't,

899
00:35:23.530 --> 00:35:25.590
uh, we glad that it did. But anyway, if you

900
00:35:25.590 --> 00:35:27.070
get a chance to have a look at Jupiter

901
00:35:27.150 --> 00:35:28.870
through a small telescope, if you know

902
00:35:28.870 --> 00:35:30.110
someone who's got a scope, if you don't have

903
00:35:30.110 --> 00:35:32.150
one yourself, really do take the opportunity

904
00:35:32.150 --> 00:35:34.550
because it's quite an amazing site. And that,

905
00:35:34.550 --> 00:35:35.910
Stuart, is for sky for October.

906
00:35:35.910 --> 00:35:37.990
Stuart Gary: That's senior science writer and sky and

907
00:35:37.990 --> 00:35:39.750
Telescope magazine contributor Jonathan

908
00:35:39.750 --> 00:35:41.790
Nally. And this is Space Time.

909
00:35:57.400 --> 00:36:00.400
And that's the show for now. Space Time is

910
00:36:00.400 --> 00:36:02.520
available every Monday, Wednesday and Friday

911
00:36:02.520 --> 00:36:05.080
through bytes.com, soundcloud,

912
00:36:05.160 --> 00:36:07.400
YouTube, your favourite podcast download

913
00:36:07.400 --> 00:36:08.690
provider provider, and from

914
00:36:08.690 --> 00:36:10.850
spacetimewithstuartgarry.com

915
00:36:11.410 --> 00:36:13.370
spacetime's also broadcast through the

916
00:36:13.370 --> 00:36:15.610
National Science foundation on Science Zone

917
00:36:15.610 --> 00:36:18.090
Radio and on both iHeartradio and

918
00:36:18.090 --> 00:36:21.010
TuneIn radio. And you can help to support our

919
00:36:21.010 --> 00:36:23.450
show by visiting the Space Time Store for a

920
00:36:23.450 --> 00:36:25.650
range of promotional merchandising goodies,

921
00:36:25.890 --> 00:36:28.730
or by becoming a Space patron, which gives

922
00:36:28.730 --> 00:36:30.890
you access to triple episode commercial free

923
00:36:30.890 --> 00:36:32.890
versions of the show as well as lots of

924
00:36:32.890 --> 00:36:34.980
bonuses, audio content which doesn't go to

925
00:36:34.980 --> 00:36:37.500
air, access to our exclusive Facebook group

926
00:36:37.500 --> 00:36:39.940
and other rewards. Just go to

927
00:36:39.940 --> 00:36:42.420
spacetimewithstuartgarry.com for full

928
00:36:42.420 --> 00:36:45.420
details. You've been listening to Space Time

929
00:36:45.420 --> 00:36:47.900
with Stuart Gary. This has been another

930
00:36:47.900 --> 00:36:50.860
quality podcast production from bytes.com.