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00:00:00 --> 00:00:03 Stuart Gary: This is space Time Series 29, episode 118
00:00:03 --> 00:00:05 for broadcast on 2nd October
00:00:05 --> 00:00:08 2026. Coming up on Space,
00:00:08 --> 00:00:11 a, uh, lost galaxy hiding deep inside the
00:00:11 --> 00:00:14 Milky Way. NASA to launch a new far
00:00:14 --> 00:00:16 infrared Space Telescope and
00:00:16 --> 00:00:19 discovery of a huge new crater on the surface
00:00:19 --> 00:00:22 of the Moon. All that and more coming up
00:00:22 --> 00:00:23 on Space Time.
00:00:25 --> 00:00:27 Welcome to Space Time with Stuart
00:00:27 --> 00:00:28 G.
00:00:44 --> 00:00:46 Astronomers have discovered a group of 20
00:00:46 --> 00:00:49 stars deep inside the Milky Way which may
00:00:49 --> 00:00:51 once have been part of a different galaxy.
00:00:51 --> 00:00:54 The findings, reported in the Monthly Notices
00:00:54 --> 00:00:56 of the Royal Astronomical Society, show how
00:00:56 --> 00:00:58 galaxies like our Milky Way grow and evolve
00:00:58 --> 00:01:00 by merging with or cannibalising other
00:01:00 --> 00:01:03 galaxies. Astronomers are able to
00:01:03 --> 00:01:05 identify the stellar remnants of other
00:01:05 --> 00:01:07 galaxies within the Milky Way because of
00:01:07 --> 00:01:09 their proper motion through space, that is
00:01:09 --> 00:01:12 the eccentricities of their galactic orbits
00:01:12 --> 00:01:14 or by their chemical composition, both of
00:01:14 --> 00:01:16 which are often very different from home
00:01:16 --> 00:01:19 grown stars in the Milky Way. This newly
00:01:19 --> 00:01:21 identified group of stars thought to have
00:01:21 --> 00:01:23 originally formed together in a dwarf galaxy
00:01:23 --> 00:01:26 which the authors have now named Loki, which
00:01:26 --> 00:01:27 must have merged with the Milky Way during
00:01:27 --> 00:01:30 its early evolution. These 20 stars are
00:01:30 --> 00:01:33 all metal poor, I.e. they contain fewer heavy
00:01:33 --> 00:01:35 elements compared to most Milky Way stars.
00:01:36 --> 00:01:38 But they're also very distinct from other low
00:01:38 --> 00:01:40 metallicity stars found further out in the
00:01:40 --> 00:01:43 halo of the Milky Way. Astronomers
00:01:43 --> 00:01:45 refer to all elements other than hydrogen and
00:01:45 --> 00:01:47 helium as metals. The earliest stars in the
00:01:47 --> 00:01:49 universe were made up almost exclusively of
00:01:49 --> 00:01:51 hydrogen and helium, because that's all there
00:01:51 --> 00:01:54 was. Following the Big Bang 13.8 billion
00:01:54 --> 00:01:57 years ago. Virtually all the other elements
00:01:57 --> 00:01:59 that make up today's periodic table were
00:01:59 --> 00:02:02 first created out of these first stars,
00:02:02 --> 00:02:04 either during their lives or when they died.
00:02:05 --> 00:02:07 And as more and more generations of stars
00:02:07 --> 00:02:10 were born, they were able to fuse heavier and
00:02:10 --> 00:02:13 heavier elements together. So by determining
00:02:13 --> 00:02:15 the metallicity of a star, astronomers can
00:02:15 --> 00:02:17 determine a star's generational age.
00:02:17 --> 00:02:19 Stars with relatively small amounts of
00:02:19 --> 00:02:21 heavier elements like iron are ah, referred
00:02:21 --> 00:02:24 to as metal pore or low metallicity.
00:02:24 --> 00:02:26 And early galaxies made up of these stars
00:02:26 --> 00:02:28 were the building blocks of the early
00:02:28 --> 00:02:31 universe. Over aeons, these
00:02:31 --> 00:02:33 galactic building blocks merged together,
00:02:33 --> 00:02:35 dispersing their stellar gaseous and dark
00:02:35 --> 00:02:37 matter content into the next generation of
00:02:37 --> 00:02:40 galaxies. Stellar surveys of the
00:02:40 --> 00:02:42 Milky Way have shown that most low
00:02:42 --> 00:02:44 metallicity stars are located in the galactic
00:02:44 --> 00:02:47 halo around the outskirts of the galaxy. But
00:02:47 --> 00:02:49 this new study looked at the chemical
00:02:49 --> 00:02:52 composition of A group of 20 metal pore stars
00:02:52 --> 00:02:54 located far away from the galactic halo in
00:02:54 --> 00:02:57 the disc of the Milky Way. The group
00:02:57 --> 00:02:59 contained both prograde and retrograde
00:02:59 --> 00:03:02 stars, all with fairly high eccentricities.
00:03:02 --> 00:03:04 The star's chemical compositions were
00:03:04 --> 00:03:06 compared to those of halo stars, dwarf
00:03:06 --> 00:03:09 galaxies and computer simulated models.
00:03:09 --> 00:03:11 The authors found that the chemical
00:03:11 --> 00:03:13 signatures in this group of 20 stars
00:03:13 --> 00:03:15 suggested enrichment from high energy
00:03:15 --> 00:03:17 supernovae, from hypernovae, from fast
00:03:17 --> 00:03:20 rotating massive stars, and from neutron star
00:03:20 --> 00:03:23 mergers, but no white dwarf explosions.
00:03:23 --> 00:03:25 And they say this suggests that this group of
00:03:25 --> 00:03:28 stars likely all originated in a short lived
00:03:28 --> 00:03:31 energetic dwarf galaxy. The compositions were
00:03:31 --> 00:03:33 the same for both prograde and retrograde
00:03:33 --> 00:03:36 orbiting stars, again suggesting similar
00:03:36 --> 00:03:39 origins. Overall, the authors say the
00:03:39 --> 00:03:40 results suggest that these stars all came
00:03:40 --> 00:03:43 from a distinct and separate origin compared
00:03:43 --> 00:03:45 to the metal pore stars in the galactic halo.
00:03:45 --> 00:03:47 Uh, this is space time
00:03:48 --> 00:03:50 still to come NASA to launch a new Far
00:03:50 --> 00:03:53 Infrared Space Telescope and discovery of a
00:03:53 --> 00:03:55 new crater on the surface of the Moon. All
00:03:55 --> 00:03:58 that and more still to come on space time,
00:04:04 --> 00:04:06 NASA has announced a new mission to use a Far
00:04:06 --> 00:04:08 Infrared Space Telescope to explore the
00:04:08 --> 00:04:10 history and evolution of the universe.
00:04:11 --> 00:04:13 The Probe Far Infrared Mission for
00:04:13 --> 00:04:15 Astrophysics, or prima, will be the first of
00:04:15 --> 00:04:18 a new class of NASA astrophysics missions
00:04:18 --> 00:04:21 called probe explorers. NASA's Jet
00:04:21 --> 00:04:23 Propulsion Laboratory in Pasadena, California
00:04:23 --> 00:04:26 will manage the $1.2 billion Space Based
00:04:26 --> 00:04:28 Observatory, which is slated for launch in
00:04:28 --> 00:04:31 2033 on UM, an initial five year
00:04:31 --> 00:04:33 mission. The spacecraft will use a
00:04:33 --> 00:04:36 1.8-metre telescope to undertake deep
00:04:36 --> 00:04:38 surveys of the universe in the far infrared,
00:04:38 --> 00:04:40 helping to bridge the gap between existing
00:04:40 --> 00:04:43 infrared observatories like NASA's Webb Space
00:04:43 --> 00:04:45 Telescope and radio telescopes which operate
00:04:45 --> 00:04:47 at millimetre, submillimeter and radio
00:04:47 --> 00:04:50 wavelengths. By studying radiant energy
00:04:50 --> 00:04:52 that only emerges in the far infrared, PRIMA
00:04:52 --> 00:04:54 will address questions about the universe,
00:04:54 --> 00:04:57 including the origins of planets outside our
00:04:57 --> 00:04:59 solar system, how galaxies and their black
00:04:59 --> 00:05:01 holes have grown and evolved over cosmic
00:05:01 --> 00:05:04 history, and how dust and heavy elements have
00:05:04 --> 00:05:06 built up in the universe across aeons, all
00:05:06 --> 00:05:09 helping to paint a better picture of why the
00:05:09 --> 00:05:10 universe looks the way it does today.
00:05:11 --> 00:05:14 NASA Associate Administrator Nikki Fox says
00:05:14 --> 00:05:16 the PRIMA mission is humanity's next window
00:05:16 --> 00:05:19 into the deep universe, unveiling the obscure
00:05:19 --> 00:05:22 across cosmic time to better understand the
00:05:22 --> 00:05:24 formation of planets, stars, black holes, and
00:05:24 --> 00:05:27 even how water came to Earth. Following
00:05:27 --> 00:05:29 its selection, the PRIMA project will now
00:05:29 --> 00:05:31 move into Phase B, which will advance the
00:05:31 --> 00:05:33 preliminary design and technology for the
00:05:33 --> 00:05:36 development of the mission. And needless to
00:05:36 --> 00:05:38 say, we'll keep you informed. This
00:05:38 --> 00:05:41 is space time still to come.
00:05:41 --> 00:05:44 NASA discovers a huge new crater on the Moon
00:05:44 --> 00:05:47 and the Alpha Centauri star system. The Large
00:05:47 --> 00:05:49 and Small Magellanic Clouds and no less than
00:05:49 --> 00:05:52 three meteor showers are among the highest
00:05:52 --> 00:05:54 highlights of the October night skies on
00:05:54 --> 00:05:55 Skywatch.
00:06:10 --> 00:06:11 Scientists have discovered a huge new
00:06:11 --> 00:06:13 asteroid impact crater on the moon.
00:06:14 --> 00:06:17 Astronomers say the steep sided, 222
00:06:17 --> 00:06:20 metre wide crater is 43 metres deep and was
00:06:20 --> 00:06:22 made about two years ago, but was initially
00:06:22 --> 00:06:24 unnoticed. The impact also escaped real
00:06:24 --> 00:06:27 time detection by telescopes on Earth and in
00:06:27 --> 00:06:29 space. It was NASA's Lunar Reconnaissance
00:06:29 --> 00:06:32 Orbiter spacecraft which detected the then
00:06:32 --> 00:06:34 newly formed crater on the moon's near side
00:06:34 --> 00:06:37 in May 2024. But scientists
00:06:37 --> 00:06:39 remained unaware of the impact event, so they
00:06:39 --> 00:06:41 got around to studying the data from the
00:06:41 --> 00:06:42 Lunar Reconnaissance Orbiter back in August
00:06:42 --> 00:06:45 last year. They then instructed the orbiter
00:06:45 --> 00:06:47 to gather more images of the impact feature,
00:06:47 --> 00:06:50 resulting in a final confirmation. It appears
00:06:50 --> 00:06:52 the impact event ejected a debris trail on
00:06:52 --> 00:06:54 the lunar surface more than 100 kilometres
00:06:54 --> 00:06:57 long. Mark Robinson, the
00:06:57 --> 00:06:59 chief scientist for the Lunar Reconnaissance
00:06:59 --> 00:07:01 Orbiter's cameras, says dust and rocky
00:07:01 --> 00:07:03 regolith were hurled away at a higher angle
00:07:03 --> 00:07:06 than expected. A separate study identified
00:07:06 --> 00:07:08 a seven kilometre wide cold spot near the new
00:07:08 --> 00:07:10 crater, consistent with the loosening of
00:07:10 --> 00:07:13 lunar regolith from the impact. The crate has
00:07:13 --> 00:07:15 been named after the late Thomas McGretchen,
00:07:15 --> 00:07:17 former director of Houston's Lunar and
00:07:17 --> 00:07:19 Planetary Institute. A report in the journal
00:07:19 --> 00:07:22 Science Advances claims it's the solar
00:07:22 --> 00:07:24 system's biggest known impact crater in
00:07:24 --> 00:07:26 recent times and three times larger than
00:07:26 --> 00:07:28 Lunar Reconnaissance Orbiter's previous
00:07:28 --> 00:07:30 record holder more than a decade ago. The
00:07:30 --> 00:07:33 authors say craters of this size usually only
00:07:33 --> 00:07:36 happen once every 132 years, effectively
00:07:36 --> 00:07:38 a once in a lifetime observation.
00:07:38 --> 00:07:41 Robinson says Lunar Reconnaissance Orbiter's
00:07:41 --> 00:07:43 numerous crater discoveries since its launch
00:07:43 --> 00:07:46 in 2009 showed that the moon's top 2 to 3
00:07:46 --> 00:07:48 centimetres of regolith is being overturned
00:07:48 --> 00:07:51 by ejected material roughly every 80
00:07:51 --> 00:07:53 years, which is faster than previously
00:07:53 --> 00:07:55 thought by Moon standards. It's lunar
00:07:55 --> 00:07:58 gardening at high speed, he says NASA's
00:07:58 --> 00:08:00 scientists will now need to calculate the
00:08:00 --> 00:08:02 risk of ejected crater materials striking the
00:08:02 --> 00:08:05 agency's planned moon base. That information
00:08:05 --> 00:08:07 will help engineers hardened structures to
00:08:07 --> 00:08:10 better protect future crew members. This
00:08:10 --> 00:08:11 is space time.
00:08:27 --> 00:08:29 And time now to turn our eyes to the skies
00:08:29 --> 00:08:31 and check out the celestial sphere for
00:08:31 --> 00:08:34 October. On skywatch, October is
00:08:34 --> 00:08:36 the tenth month of the year. And that may
00:08:36 --> 00:08:39 seem confusing since octo Latin Latin means
00:08:39 --> 00:08:41 eight rather than ten. The answer lies
00:08:41 --> 00:08:44 in the old Roman calendar, which had just 10
00:08:44 --> 00:08:46 months before the addition of January and
00:08:46 --> 00:08:49 February. And that 10 month year is still
00:08:49 --> 00:08:52 reflected today, with the name September or
00:08:52 --> 00:08:55 septum being Latin for 7, October or
00:08:55 --> 00:08:57 Octo meaning 8, November or November
00:08:57 --> 00:09:00 9 and December or Deci meaning 10.
00:09:01 --> 00:09:04 Of course, the highlight of October for kids
00:09:04 --> 00:09:06 and those who are young at Heart has to be
00:09:06 --> 00:09:08 the last day of the month celebrated as All
00:09:08 --> 00:09:10 Hallows Evening, or Halloween.
00:09:11 --> 00:09:14 Halloween is based on ancient Celtic pagan
00:09:14 --> 00:09:16 festivals such as Samhain, uh, the Gaelic
00:09:16 --> 00:09:19 festival of the dead. Samhain was eventually
00:09:19 --> 00:09:21 Christianized by the early church to become
00:09:21 --> 00:09:24 All Saints or All Hallows Eve, or simply
00:09:24 --> 00:09:26 Halloween. It's a time when darkness
00:09:26 --> 00:09:29 overtakes the light of day, a reference to
00:09:29 --> 00:09:31 the increasing hours of darkness as the
00:09:31 --> 00:09:34 planet's northern hemisphere moves towards
00:09:34 --> 00:09:36 longer winter nights. And so it's a time
00:09:36 --> 00:09:39 when the harvest comes to an end. The
00:09:39 --> 00:09:42 increased hours of darkness mean the boundary
00:09:42 --> 00:09:44 between the world of the living and the world
00:09:44 --> 00:09:46 of the dead becomes especially thin,
00:09:47 --> 00:09:49 allowing the dead and supernatural to rise
00:09:49 --> 00:09:52 in search of the living. And so the living
00:09:52 --> 00:09:55 wear disguises so as not to be recognised by
00:09:55 --> 00:09:57 the dead. And it's this which has led to
00:09:57 --> 00:09:59 today's tradition of the Halloween fancy
00:09:59 --> 00:10:02 dress party. In some parts of the world,
00:10:02 --> 00:10:04 cross dressing is popular on Halloween, a
00:10:04 --> 00:10:06 reflection of the secret desires and
00:10:06 --> 00:10:08 fantasies of their pagan ancestors,
00:10:09 --> 00:10:11 sometimes not so many generations removed.
00:10:12 --> 00:10:14 To ensure that crops and livestock survived
00:10:14 --> 00:10:17 the cold winter months ahead, offerings of
00:10:17 --> 00:10:19 food and drink would be left outside for the
00:10:19 --> 00:10:22 spirits and fairies of the other side. And it
00:10:22 --> 00:10:24 was this which ultimately led to today's
00:10:24 --> 00:10:26 practice of trick or treat. Also,
00:10:26 --> 00:10:29 candles would be lit and prayers offered to
00:10:29 --> 00:10:31 the souls of the dead, as Halloween was a
00:10:31 --> 00:10:33 time when the spirits of the dead would
00:10:33 --> 00:10:36 return to their former homes. Special
00:10:36 --> 00:10:38 bonfires were also lit on Halloween to light
00:10:38 --> 00:10:41 the darkness, thereby preventing souls of the
00:10:41 --> 00:10:43 dead from returning and keeping the evil
00:10:43 --> 00:10:46 away. The flames, smoke and ashes
00:10:46 --> 00:10:48 were deemed to have protective and cleansing
00:10:48 --> 00:10:51 powers and were used for divination. As
00:10:51 --> 00:10:53 for the tradition of carving pumpkins into
00:10:53 --> 00:10:55 jack o', lanterns, well, that was originally
00:10:55 --> 00:10:57 meant either to represent spirits or
00:10:57 --> 00:11:00 supernatural beings, or alternatively, to
00:11:00 --> 00:11:01 ward off evil spirits.
00:11:02 --> 00:11:04 In many parts of the world, the Christian
00:11:04 --> 00:11:07 religious observances of All Hallows Eve
00:11:07 --> 00:11:09 include attending church services and
00:11:09 --> 00:11:11 lighting candles on the graves of the dead.
00:11:12 --> 00:11:14 And Christians historically abstained from
00:11:14 --> 00:11:16 eating meat on All Hallows Eve. A, uh,
00:11:16 --> 00:11:18 tradition reflected in the eating of certain
00:11:18 --> 00:11:21 vegetable foods on the day, including apples,
00:11:21 --> 00:11:23 potato pancakes and soul cakes.
00:11:24 --> 00:11:26 Apple bobbing originated because the apple
00:11:26 --> 00:11:29 was a Celtic symbol of love, and so grabbing
00:11:29 --> 00:11:31 the apple with your teeth had certain erotic
00:11:31 --> 00:11:34 overtones. Halloween is a time
00:11:34 --> 00:11:37 of fortune telling and divination games,
00:11:37 --> 00:11:39 playing pranks to scare people, visiting
00:11:39 --> 00:11:42 haunted attractions, telling scary stories,
00:11:42 --> 00:11:44 and, of course, watching horror movies.
00:11:46 --> 00:11:48 Looking to the southwest, you'll see the two
00:11:48 --> 00:11:50 bright pointed stars which show the way to
00:11:50 --> 00:11:53 the Southern cross, the brightest and what
00:11:53 --> 00:11:55 also looks like the more distant of the two
00:11:55 --> 00:11:57 stars from the Southern Cross is Alpha
00:11:57 --> 00:12:00 Centauri, which is actually the nearest star
00:12:00 --> 00:12:03 system to our own solar system. Alpha
00:12:03 --> 00:12:05 Centauri is a triple star system comprising
00:12:05 --> 00:12:08 two stars, Alpha Centauri A and B, which
00:12:08 --> 00:12:10 orbit each other in a binary, and a third
00:12:10 --> 00:12:13 star, Proxima Centauri, which orbit the pair
00:12:14 --> 00:12:16 like the Sun, Alpha Centauri E is a spectral
00:12:16 --> 00:12:19 type G yellow dwarf star. It's about
00:12:19 --> 00:12:22 10% more massive than our sun and about one
00:12:22 --> 00:12:24 and a half times as luminous.
00:12:24 --> 00:12:27 Astronomers describe stars in terms of
00:12:27 --> 00:12:30 spectral types. It's a classification
00:12:30 --> 00:12:32 system based on temperature and
00:12:32 --> 00:12:34 characteristics. The hottest, most massive
00:12:34 --> 00:12:37 and most luminous stars are known as spectral
00:12:37 --> 00:12:40 type O blue stars. They are followed
00:12:40 --> 00:12:43 by spectral type B blue white stars. Then
00:12:43 --> 00:12:46 spectral type A white stars, spectral
00:12:46 --> 00:12:49 type F, whitish yellow stars, spectral
00:12:49 --> 00:12:51 type G yellow stars. That's where our sun
00:12:51 --> 00:12:53 fits in. Spectral type K orange
00:12:53 --> 00:12:54 stars.
00:12:54 --> 00:12:57 And the coolest and least massive stars of
00:12:57 --> 00:13:00 all are the spectral type M red stars.
00:13:00 --> 00:13:02 Each spectral classification is also
00:13:02 --> 00:13:05 subdivided using a numeric digit to represent
00:13:05 --> 00:13:07 temperature, with zero being the hottest and
00:13:07 --> 00:13:09 nine the coolest, and a Roman numeral to
00:13:09 --> 00:13:12 represent luminosity. Now, you pull all that
00:13:12 --> 00:13:15 together and our sun becomes a G2V
00:13:15 --> 00:13:18 or G25 yellow dwarf star.
00:13:19 --> 00:13:21 Also included in the stellar classification
00:13:21 --> 00:13:24 system are spectral types LT and Y,
00:13:24 --> 00:13:26 which are assigned to failed stars known as
00:13:26 --> 00:13:28 brown dwarfs, some of which were actually
00:13:28 --> 00:13:31 born as spectral type um M red stars, but
00:13:31 --> 00:13:33 became brown dwarves after losing some of
00:13:33 --> 00:13:36 their mass. Brown dwarfs fit into a unique
00:13:36 --> 00:13:39 category between the largest planets, which
00:13:39 --> 00:13:41 can be up to 13 times the Mass of Jupiter,
00:13:41 --> 00:13:44 and the smallest stars, those spectral
00:13:44 --> 00:13:46 type M red dwarf stars we mentioned earlier.
00:13:47 --> 00:13:50 These can be 75 to 80 times the mass of
00:13:50 --> 00:13:52 Jupiter, or about 0.08
00:13:52 --> 00:13:55 solar masses. Alpha Centauri
00:13:55 --> 00:13:58 A's binary partner, Alpha Centauri B, is
00:13:58 --> 00:14:01 a special type K orange dwarf star, a
00:14:01 --> 00:14:03 little smaller and cooler than its companion,
00:14:03 --> 00:14:06 with about 90% of the Sun's mass and about
00:14:06 --> 00:14:09 half its luminosity. This binary
00:14:09 --> 00:14:12 pair, Alpha Centauri A and B, orbit each
00:14:12 --> 00:14:14 other at between 11.2 and
00:14:14 --> 00:14:17 35.6 astronomical units.
00:14:17 --> 00:14:19 An astronomical unit is the average distance
00:14:19 --> 00:14:22 between the Earth and the sun, which equates
00:14:22 --> 00:14:24 to about 150 million kilometres, or around
00:14:24 --> 00:14:27 8.3 light minutes. So the
00:14:27 --> 00:14:30 pair's orbit around each other varies by
00:14:30 --> 00:14:32 between the average distance between the sun
00:14:32 --> 00:14:34 and Saturn and between the sun and Pluto.
00:14:35 --> 00:14:38 It takes the two stars 79.91
00:14:38 --> 00:14:41 Earth years to complete each orbit. On
00:14:41 --> 00:14:44 average, Alpha Centauri A and b are located
00:14:44 --> 00:14:46 4.37 light years from the Sun.
00:14:47 --> 00:14:49 Uh, although a light year sounds like a
00:14:49 --> 00:14:51 measure of time, it's actually a measure of
00:14:51 --> 00:14:54 distance. A light year is a distance of about
00:14:54 --> 00:14:57 10 trillion kilometres. That's the distance a
00:14:57 --> 00:14:59 photon can travel in a year at the speed of
00:14:59 --> 00:15:02 light, which is around 300 kilometres per
00:15:02 --> 00:15:04 second in a vacuum and the ultimate speed
00:15:04 --> 00:15:05 limit of the universe.
00:15:06 --> 00:15:08 The third star in the Alpha Centauri system
00:15:08 --> 00:15:11 is a spectral type M red dwarf star named
00:15:11 --> 00:15:14 Proxima Centauri. Right now, Proxima
00:15:14 --> 00:15:17 Centauri is just 4.25 light years away,
00:15:17 --> 00:15:19 making it the nearest star to the Earth other
00:15:19 --> 00:15:22 than the Sun. It is only loosely
00:15:22 --> 00:15:24 gravitationally bound to Alpha Centauri A and
00:15:24 --> 00:15:27 B, orbiting the pair at an average distance
00:15:27 --> 00:15:30 of 13 astronomical units, or
00:15:30 --> 00:15:32 around 0.21 light years.
00:15:32 --> 00:15:35 That's about 430 times the size of
00:15:35 --> 00:15:37 Neptune's 30 astronomical unit orbit around
00:15:37 --> 00:15:40 the sun. In 2016,
00:15:40 --> 00:15:42 astronomers confirmed the existence of an
00:15:42 --> 00:15:44 Earth sized terrestrial planet orbiting
00:15:44 --> 00:15:46 within the habitable zone of Proxima
00:15:46 --> 00:15:48 Centauri, making it the nearest known
00:15:48 --> 00:15:51 extrasolar or exoplanet to Earth.
00:15:51 --> 00:15:54 The habitable zone, which is sometimes also
00:15:54 --> 00:15:56 referred to as the Goldilocks zone, um, is
00:15:56 --> 00:15:58 that area out from a star where it's not too
00:15:58 --> 00:16:01 hot, not too cold, but just right for
00:16:01 --> 00:16:04 liquid water, essential for life as we know
00:16:04 --> 00:16:07 it to exist on the planet's surface. The
00:16:07 --> 00:16:09 planet known as Proxima B takes just 11
00:16:09 --> 00:16:11 Earth days to complete one orbit around its
00:16:11 --> 00:16:14 host star. Uh, that's far closer than
00:16:14 --> 00:16:17 Mercury's 88 Earth Day orbit around the Sun.
00:16:18 --> 00:16:20 A few years ago, a second more distant
00:16:20 --> 00:16:23 planet, Proxima C was also discovered
00:16:23 --> 00:16:26 orbiting around the star, but well outside
00:16:26 --> 00:16:28 its habitable zone. The second and
00:16:28 --> 00:16:31 slightly fainter of the two Pointer stars is
00:16:31 --> 00:16:34 Beta Centauri. And while Alpha Centauri is
00:16:34 --> 00:16:35 the third brightest star in the night, uh,
00:16:35 --> 00:16:38 sky, outshone only by Sirius and
00:16:38 --> 00:16:41 Canopus, Beta Centauri is only about the 10th
00:16:41 --> 00:16:44 brightest. Looking to the southeast
00:16:44 --> 00:16:46 and you'll see the bright blue white star
00:16:46 --> 00:16:49 Alpha Eridni or Achenar, which represents the
00:16:49 --> 00:16:51 southern tip of Eridanus, one of the largest
00:16:51 --> 00:16:53 and longest constellations in the sky.
00:16:54 --> 00:16:56 Achenar is located about 139 light
00:16:56 --> 00:16:59 years away. It's actually a binary
00:16:59 --> 00:17:02 star system comprising two stars, Alpha
00:17:02 --> 00:17:04 Eridani A and Alpha Rhydmi B.
00:17:05 --> 00:17:07 Alpha Riddinier is a height, young, spectral
00:17:07 --> 00:17:09 type B blue star. It has about
00:17:09 --> 00:17:12 6.7 times the mass of the sun and a
00:17:12 --> 00:17:15 stunning 3 times the sun's
00:17:15 --> 00:17:16 luminosity.
00:17:17 --> 00:17:19 By comparison, the companion star Alpha Rydni
00:17:19 --> 00:17:22 B appears to be a spectra type A white star
00:17:22 --> 00:17:25 with about twice the Sun's mass. The
00:17:25 --> 00:17:28 two stars orbit each other every 1415
00:17:28 --> 00:17:30 Earth years at an average distance of about
00:17:30 --> 00:17:33 12.3 astronomical units.
00:17:33 --> 00:17:35 Because of its high rotation rate of, uh,
00:17:35 --> 00:17:38 over 16 kilometres per second, Alpha Eridani
00:17:38 --> 00:17:40 A is actually one of the least spherical
00:17:40 --> 00:17:43 stars in the Milky Way. Spinning so
00:17:43 --> 00:17:45 rapidly, it's assumed the shape of an oblique
00:17:45 --> 00:17:48 spheroid with an equatorial diameter
00:17:48 --> 00:17:50 56% greater than its polar diameter.
00:17:51 --> 00:17:53 This distorted shape means the star displays
00:17:53 --> 00:17:56 a significant latitudinal temperature, with
00:17:56 --> 00:17:58 its polar temperature being about 20
00:17:58 --> 00:18:00 Kelvin, while its equatorial temperature is
00:18:00 --> 00:18:02 only around 10 Kelvin. That's because
00:18:02 --> 00:18:05 it's much further away from its stellar core.
00:18:05 --> 00:18:07 The high polar temperatures, uh, are
00:18:07 --> 00:18:10 generating a fast polar wind that's
00:18:10 --> 00:18:13 ejecting matter from the star and creating a
00:18:13 --> 00:18:16 spectacular polar envelope of hot gas and
00:18:16 --> 00:18:19 plasma. Now, if you look up between the
00:18:19 --> 00:18:21 South Celestial Pole and Achana from a really
00:18:21 --> 00:18:24 dark place, you'll see two faint, fuzzy
00:18:24 --> 00:18:27 looking clouds. Now, these aren't actually
00:18:27 --> 00:18:30 clouds. There are two satellite dwarf
00:18:30 --> 00:18:32 galaxies which orbit the Milky Way. Known as
00:18:32 --> 00:18:35 the Large and Small Magellanic Clouds,
00:18:35 --> 00:18:37 they're named after Ferdinand Magellan, who
00:18:37 --> 00:18:39 became the first European to officially
00:18:39 --> 00:18:41 record them during his expedition to
00:18:41 --> 00:18:44 circumnavigate the Earth between 1519 and
00:18:44 --> 00:18:47 1522. The bigger and
00:18:47 --> 00:18:49 nearer of the pair is the Large Magellanic
00:18:49 --> 00:18:52 Cloud, which is located around 160 light
00:18:52 --> 00:18:55 years away. It's easier to spot about
00:18:55 --> 00:18:57 halfway between Achenar and the Horizon.
00:18:58 --> 00:19:01 It's about 14 light years across,
00:19:01 --> 00:19:03 twice that of the Small Magellanic Cloud,
00:19:03 --> 00:19:06 which is located a more distant 200 light
00:19:06 --> 00:19:09 years from the Milky Way. Now, by comparison
00:19:09 --> 00:19:11 to these two satellite galaxies, the Milky
00:19:11 --> 00:19:14 Way is huge, 100 light years across.
00:19:15 --> 00:19:17 These two dwarf galaxies are separated from
00:19:17 --> 00:19:20 each other by roughly 75 light years.
00:19:20 --> 00:19:22 The Magellanic Clouds were considered the
00:19:22 --> 00:19:25 closest galaxies to the Milky way until the
00:19:25 --> 00:19:28 1994 discovery of the Sagittarius Dwarf
00:19:28 --> 00:19:30 Elliptical Galaxy and the 2003
00:19:30 --> 00:19:32 confirmation that the Canis Major dwarf
00:19:32 --> 00:19:35 galaxy is actually our nearest galactic
00:19:35 --> 00:19:37 neighbour. The total mass of the Magellanic
00:19:37 --> 00:19:40 Clouds is uncertain. Only a fraction of their
00:19:40 --> 00:19:42 gas seems to have coalesced into stars. And
00:19:42 --> 00:19:44 they also probably both have very large dark
00:19:44 --> 00:19:47 matter halos. Still, one recent estimate
00:19:47 --> 00:19:50 places the total mass of the Large Magellanic
00:19:50 --> 00:19:52 Cloud at about one tenth that of the Milky
00:19:52 --> 00:19:54 Way. The Magellanic Clouds have both been
00:19:54 --> 00:19:57 greatly distorted by gravitational tidal
00:19:57 --> 00:20:00 interactions as they're gradually torn apart
00:20:00 --> 00:20:03 and absorbed by the Milky Way. These
00:20:03 --> 00:20:05 huge tidal forces have turned both
00:20:05 --> 00:20:08 Magellanic Clouds into irregular, disrupted,
00:20:08 --> 00:20:11 barred spiral galaxies. The Large
00:20:11 --> 00:20:13 Magellanic Cloud still retains a very clear
00:20:13 --> 00:20:16 spiral structure, at least in radio telescope
00:20:16 --> 00:20:18 images of neutral hydrogen. But
00:20:18 --> 00:20:21 gravity isn't a one way street, and the
00:20:21 --> 00:20:23 combined gravitational force of both
00:20:23 --> 00:20:25 Magellanic Clouds is also affecting the Milky
00:20:25 --> 00:20:27 Way, distorting the outer parts of our
00:20:27 --> 00:20:30 galactic disc. And there are streams of
00:20:30 --> 00:20:33 neutral hydrogen gas clouds and isolated
00:20:33 --> 00:20:36 stars connecting both dwarf galaxies to
00:20:36 --> 00:20:39 each other and to the Milky Way. A brilliant
00:20:39 --> 00:20:41 example of galactic cannibalism at work.
00:20:42 --> 00:20:44 Now, if you look just above the Small
00:20:44 --> 00:20:46 Magellanic Cloud, using a backyard telescope
00:20:46 --> 00:20:49 or a good pair of binoculars, you'll see a
00:20:49 --> 00:20:51 small blurry dot that is the
00:20:51 --> 00:20:54 47 Tucanae globular cluster,
00:20:54 --> 00:20:57 a tightly packed ball of stars some 16
00:20:57 --> 00:20:59 light years away that were all originally
00:20:59 --> 00:21:01 formed at the same time through the
00:21:01 --> 00:21:03 gravitational collapse of the same molecular
00:21:03 --> 00:21:06 gas and dust cloud. If you look
00:21:06 --> 00:21:08 to the west, you'll see the bright reddish
00:21:08 --> 00:21:11 orange supergiant star Antares, the heart of
00:21:11 --> 00:21:13 the constellation Scorpius the Scorpion.
00:21:14 --> 00:21:16 And above it, you'll see a bunch of stars
00:21:16 --> 00:21:18 stretching out, shaped like a reverse
00:21:18 --> 00:21:18 question mark.
00:21:19 --> 00:21:20 That's the tail of the Scorpion.
00:21:22 --> 00:21:24 Now, just above and to the north is the
00:21:24 --> 00:21:26 constellation Sagittarius the Archer.
00:21:27 --> 00:21:29 Sagittarius shows the way to the supermassive
00:21:29 --> 00:21:31 black hole at the centre of the Milky way
00:21:31 --> 00:21:34 galaxy, some 27 light years away.
00:21:34 --> 00:21:37 This monster black hole, known as Sagittarius
00:21:37 --> 00:21:40 a, has about 4.3 million
00:21:40 --> 00:21:42 times the mass of our Sun.
00:21:43 --> 00:21:45 Now, looking to the north northwest this time
00:21:45 --> 00:21:47 of the year, you'll see the constellation
00:21:47 --> 00:21:49 Lyra the Harp and its brightest star,
00:21:49 --> 00:21:51 Vega, the fifth brightest star in the night
00:21:51 --> 00:21:54 sky and one of the closest, at, uh, just 25
00:21:54 --> 00:21:57 light years away. Vega is a special
00:21:57 --> 00:22:00 type, a white star more than twice the size
00:22:00 --> 00:22:02 and some 40 times the mass of our Sun.
00:22:03 --> 00:22:06 Now, just to the right of Lyra and almost
00:22:06 --> 00:22:08 directly north, just above the horizon, is
00:22:08 --> 00:22:11 the constellation of Cygnus the Swan and its
00:22:11 --> 00:22:13 brightest star, Deneb, one of the most
00:22:13 --> 00:22:16 luminous stars in the sky. Deneb is a
00:22:16 --> 00:22:19 massive spectral type, a white supergiant,
00:22:19 --> 00:22:22 some 19 times the mass and over 100 times
00:22:22 --> 00:22:24 the diameter of the Sun. The star is
00:22:24 --> 00:22:26 somewhere between 55 and
00:22:26 --> 00:22:29 196 times as luminous as the
00:22:29 --> 00:22:32 Sun. The huge range in luminosity
00:22:32 --> 00:22:34 estimate is caused by the difficulty in
00:22:34 --> 00:22:36 determining Deneb's exact distance from us.
00:22:37 --> 00:22:39 Science's best estimates place it somewhere
00:22:39 --> 00:22:42 around 2600 light years away, give or take
00:22:42 --> 00:22:45 212 light years. High
00:22:45 --> 00:22:47 in the northern sky right now is the
00:22:47 --> 00:22:49 constellation Aquila the Eagle and its
00:22:49 --> 00:22:52 brightest star Altair. Altair
00:22:52 --> 00:22:55 is another spectral type, a white star, but
00:22:55 --> 00:22:58 located a lot closer. Just 17 light years
00:22:58 --> 00:23:01 away, it's about 10 times brighter than the
00:23:01 --> 00:23:03 sun with about 1.89 times the sun's
00:23:03 --> 00:23:06 mass. Despite its size, Altair spins
00:23:06 --> 00:23:09 on its axis in just 10 hours compared to our
00:23:09 --> 00:23:11 Sun's 28 Earth Day rotation.
00:23:12 --> 00:23:15 Now these three stars, Altair, Deneb and
00:23:15 --> 00:23:18 Vega form a stellar grouping known as the
00:23:18 --> 00:23:21 Summer Triangle. Now also in
00:23:21 --> 00:23:23 October, there are three meteor showers,
00:23:24 --> 00:23:26 the Draconids, the Taurids and the
00:23:26 --> 00:23:29 Orionids. The Draconids take
00:23:29 --> 00:23:32 place on October 8th. They're so
00:23:32 --> 00:23:34 named because their meteors appear to radiate
00:23:34 --> 00:23:36 out from the constellation Draco the Dragon
00:23:36 --> 00:23:39 and so are, uh, best viewed from the Northern
00:23:39 --> 00:23:41 Hemisphere. They're actually produced as the
00:23:41 --> 00:23:43 Earth's orbit takes it through the debris
00:23:43 --> 00:23:46 trail left behind by the comet 21P
00:23:46 --> 00:23:49 Shir Kobeni Zinna, which takes about 6.6
00:23:49 --> 00:23:51 Earth years to make a single revolution of
00:23:51 --> 00:23:54 the Sun. The Taurids meteor
00:23:54 --> 00:23:57 shower takes place on October 10th, and as
00:23:57 --> 00:23:58 their name suggests, they appear to radiate
00:23:58 --> 00:24:01 out from the constellation Taurus the Bull.
00:24:01 --> 00:24:03 Their meteors are composed of larger than
00:24:03 --> 00:24:06 average pebbles and dust grains and are
00:24:06 --> 00:24:08 thought to be generated by debris left behind
00:24:08 --> 00:24:11 by the Comet 2P Encke. Although
00:24:11 --> 00:24:13 it's thought that both the Taureds and Encke
00:24:13 --> 00:24:15 could be the remains of an earlier comet
00:24:15 --> 00:24:18 which disintegrated over the past 20 to
00:24:18 --> 00:24:21 30 years, breaking into several pieces
00:24:21 --> 00:24:23 and releasing material both by normal
00:24:23 --> 00:24:25 cometary activity and possibly also by
00:24:25 --> 00:24:27 gravitational tidal interactions with the
00:24:27 --> 00:24:30 Earth and other planets. The Taurids
00:24:30 --> 00:24:32 debris stream is the largest in the inner
00:24:32 --> 00:24:35 solar system, taking the Earth several weeks
00:24:35 --> 00:24:37 to pass through and resulting in an extended
00:24:37 --> 00:24:39 period of meteor activity compared to other
00:24:39 --> 00:24:42 meteor showers, which are usually over in
00:24:42 --> 00:24:44 just a matter of days. Now, due to the
00:24:44 --> 00:24:46 gravitational perturbations of the planets,
00:24:46 --> 00:24:48 especially Jupiter, the Taurids have been
00:24:48 --> 00:24:51 spread out over time, allowing separate
00:24:51 --> 00:24:53 segments labelled the Northern Taurids and
00:24:53 --> 00:24:55 Southern Taurids to be observable at
00:24:55 --> 00:24:58 different times in different hemispheres. The
00:24:58 --> 00:25:00 Southern Taurids are active from around
00:25:00 --> 00:25:02 September 10 to November 20, while the
00:25:02 --> 00:25:05 northern Taurids are active from October 20
00:25:05 --> 00:25:07 to December 10. The third
00:25:07 --> 00:25:09 meteor shower this month is the Orionids,
00:25:09 --> 00:25:12 which peak on October 20th. They're
00:25:12 --> 00:25:15 caused by debris from the comet Hallie, which
00:25:15 --> 00:25:17 also causes the Eta Achorens meteor shower in
00:25:17 --> 00:25:20 May. Comet Hallie takes 76 years
00:25:20 --> 00:25:23 to complete each orbit around the Sun. It'll
00:25:23 --> 00:25:26 next become visible near Earth in 2061.
00:25:26 --> 00:25:29 The Orionids are equally spectacular in both
00:25:29 --> 00:25:31 northern and Southern hemisphere skies, with
00:25:31 --> 00:25:34 up to 20 meteors an hour, uh, radiating out
00:25:34 --> 00:25:36 from the constellation Orion. The best
00:25:36 --> 00:25:39 time to see the Orionids is just after
00:25:39 --> 00:25:41 midnight and right before dusk.
00:25:42 --> 00:25:43 And joining us now for the rest of our tour
00:25:43 --> 00:25:46 of the October night skies is senior science
00:25:46 --> 00:25:48 writer and sky and Telescope magazine
00:25:48 --> 00:25:49 contributor, Jonathan Nally.
00:25:49 --> 00:25:51 Jonathan Nally: Hi, Stuart. Yeah, well, we're still in spring
00:25:51 --> 00:25:53 here in Australia. We're heading towards
00:25:53 --> 00:25:54 summer. I can definitely feel summer coming
00:25:54 --> 00:25:56 along. The days are feeling different. Days
00:25:56 --> 00:25:57 are nice and bright and warm, and the nights
00:25:57 --> 00:25:59 are generally clear for us at this time of
00:25:59 --> 00:26:01 year and not too cold, which is really good
00:26:01 --> 00:26:02 for stargazing. The further we get into
00:26:02 --> 00:26:05 summer, even better weather wise, you know,
00:26:05 --> 00:26:06 because it's warmer and everything. But
00:26:06 --> 00:26:08 because it's summer, the days are longer and
00:26:08 --> 00:26:10 the hours of nighttime are less. So you have
00:26:10 --> 00:26:12 better conditions for stargazing, but you
00:26:12 --> 00:26:14 have fewer hours. So this sort of late
00:26:14 --> 00:26:16 springtime, pretty good for stargazing. So
00:26:16 --> 00:26:17 let's take a look at what we can see in the
00:26:17 --> 00:26:19 south at this time of the year. So really
00:26:19 --> 00:26:20 deep in the south, we've got the famous
00:26:20 --> 00:26:22 Southern Cross, of course, now it's upside
00:26:22 --> 00:26:24 down at the moment and it's low down in the
00:26:24 --> 00:26:26 southwest, so it'll be either right on the
00:26:26 --> 00:26:28 southern horizon for a lot of people or even
00:26:28 --> 00:26:29 below it.
00:26:29 --> 00:26:31 So you can't see it for most populated
00:26:31 --> 00:26:33 southern latitudes, say Sydney or Brisbane in
00:26:33 --> 00:26:35 Australia and other cities around the
00:26:35 --> 00:26:37 Southern hemisphere, similar latitudes. But
00:26:37 --> 00:26:39 if you're as far south as in Australia, at
00:26:39 --> 00:26:40 least Melbourne or Hobart, you should still
00:26:40 --> 00:26:42 be able to see it fairly easily this time of
00:26:42 --> 00:26:44 the year. Now, panning across to the left or
00:26:44 --> 00:26:47 the east, we can find the two Magellanic
00:26:47 --> 00:26:48 Cloud galaxies. Now, these are the two
00:26:48 --> 00:26:51 nearest sizable galaxies outside our Milky
00:26:51 --> 00:26:53 Way, and they're named after the explorer
00:26:53 --> 00:26:55 Magellan, the Magellanic Galaxies. Now, these
00:26:55 --> 00:26:58 just look like two little faint fuzzy clouds.
00:26:58 --> 00:27:00 So you really need dark sky conditions to see
00:27:00 --> 00:27:02 them. If you're in a big city, you can just
00:27:02 --> 00:27:04 forget it. I can't see them where I am with
00:27:04 --> 00:27:05 the unaided eye. You've really got to get
00:27:05 --> 00:27:08 somewhere dark or away from lights and then
00:27:08 --> 00:27:10 let your eyes get adapted to the dark. And so
00:27:10 --> 00:27:11 if you then look down the southeast, you
00:27:11 --> 00:27:13 might be able to see these things. So you've
00:27:13 --> 00:27:15 got the large Cloud, which is lower down and
00:27:15 --> 00:27:17 a fair distance away from it. And higher up,
00:27:17 --> 00:27:19 you've got the Small Magellanic Cloud. And as
00:27:19 --> 00:27:21 I said, these are the. These are two fairly
00:27:21 --> 00:27:22 sizable galaxies. And they're very close to
00:27:22 --> 00:27:24 the Milky Way, which is why we can see them.
00:27:24 --> 00:27:26 Most other galaxies, uh, I'm just thinking,
00:27:26 --> 00:27:28 well, there's water, two or three
00:27:29 --> 00:27:31 maybe you can count on one hand. The other
00:27:31 --> 00:27:33 galaxy you can see with the unaided eye. Um,
00:27:33 --> 00:27:35 the Andromeda Galaxy and a couple of others.
00:27:35 --> 00:27:37 But they just look like little smudges. These
00:27:37 --> 00:27:40 Magellanic Galaxies, they are quite big,
00:27:40 --> 00:27:42 which is. They look like a cloud. They look
00:27:42 --> 00:27:44 like a fairly sizable cloud. So you'll find
00:27:44 --> 00:27:46 them low down in the southeast at this time
00:27:46 --> 00:27:48 of year. In the early evening now, we've got
00:27:48 --> 00:27:50 the Milky Way stretching from north to south
00:27:50 --> 00:27:52 across the western half of the sky after
00:27:52 --> 00:27:55 sunset with the constellation Sagittarius
00:27:55 --> 00:27:57 and the very impressive Scorpius, which
00:27:57 --> 00:27:59 really does look like a scorpion. They're
00:27:59 --> 00:28:02 easily visible high overhead. But as the
00:28:02 --> 00:28:05 night goes on, by midnight, that half of the
00:28:05 --> 00:28:07 Milky Way will have set below the horizon,
00:28:07 --> 00:28:09 the western horizon, as the Earth continues
00:28:09 --> 00:28:11 to turn now overhead. The sky
00:28:12 --> 00:28:14 seems pretty reasonably empty this time of
00:28:14 --> 00:28:15 year. There are some deep constellations up
00:28:15 --> 00:28:18 there, but they don't seem pretty exciting.
00:28:18 --> 00:28:20 They're a bit dull. Um, they don't have a lot
00:28:20 --> 00:28:22 of bright stars and things. If you get a
00:28:22 --> 00:28:24 telescope onto them, backyard telescope, you
00:28:24 --> 00:28:25 can see lots of things within them, but just
00:28:25 --> 00:28:28 to the naked eye. Capricornus, Sculptor,
00:28:28 --> 00:28:30 Aquarius, Cetus and others, um, they look
00:28:30 --> 00:28:32 fairly bland, the northern part of the sky.
00:28:33 --> 00:28:34 Apologies to our northern listeners, Northern
00:28:34 --> 00:28:36 Hemisphere listeners. But down here in the
00:28:36 --> 00:28:37 south, the bits that we can see at this time
00:28:37 --> 00:28:39 of year, it's pretty dull there as well. If
00:28:39 --> 00:28:41 we were much further north of the equator,
00:28:41 --> 00:28:43 there would be plenty of things to see. But
00:28:43 --> 00:28:45 if you like staying up late or getting up
00:28:45 --> 00:28:47 really early, the skies after midnight in
00:28:47 --> 00:28:49 October are really great. Because the other
00:28:49 --> 00:28:51 half of the Milky Way is rising in the east,
00:28:51 --> 00:28:53 bringing with it the fabulous constellations
00:28:53 --> 00:28:56 of Orion and Taurus and Gemini and Canis
00:28:56 --> 00:28:58 Major and Papus and other ones. To me, these
00:28:58 --> 00:29:01 are the constellations of, um, summer. For
00:29:01 --> 00:29:02 people in the Northern Hemisphere, they're
00:29:02 --> 00:29:04 the constellations of winter. So at the
00:29:04 --> 00:29:06 moment, you've got to be up before dawn to
00:29:06 --> 00:29:06 see them.
00:29:06 --> 00:29:08 But as the weeks go on, they'll be rising
00:29:08 --> 00:29:10 earlier and earlier and earlier. So by the
00:29:10 --> 00:29:12 time summer comes around, they'll be up
00:29:12 --> 00:29:14 invisible in the night sky just after sunset
00:29:14 --> 00:29:16 when the sky gets dark. So this, for me, is a
00:29:16 --> 00:29:19 sign that better weather is coming and better
00:29:19 --> 00:29:21 skies are coming. Lots of great stuff to see.
00:29:21 --> 00:29:23 And all of those constellations here have
00:29:23 --> 00:29:25 plenty of deep sky objects, what astronomers
00:29:25 --> 00:29:28 call deep sky objects you need telescopes
00:29:28 --> 00:29:30 for. But even a small backyard telescope, you
00:29:30 --> 00:29:32 can see star clusters and nebulae and all
00:29:32 --> 00:29:33 sorts of wonderful stuff. So, for instance,
00:29:33 --> 00:29:35 you've got the constellation Canis Major. It
00:29:35 --> 00:29:36 has the brightest star in the night sky,
00:29:36 --> 00:29:39 Sirius, Orion. Uh, it has the two bright
00:29:39 --> 00:29:41 stars, Rigel and Betelgeuse, but it also has
00:29:41 --> 00:29:43 the famous Orion Nebula. Now, the Orion
00:29:43 --> 00:29:45 Nebula is very famous in astronomy circles.
00:29:45 --> 00:29:47 Everyone's probably seen a picture of the
00:29:47 --> 00:29:47 Orion Nebula.
00:29:47 --> 00:29:49 Stuart Gary: Yeah, it's the one I always look for when I
00:29:49 --> 00:29:52 want to work out where the stars are in the
00:29:52 --> 00:29:53 sky. Either that or the Southern Cross.
00:29:53 --> 00:29:54 They're the first ones I go to.
00:29:54 --> 00:29:57 Jonathan Nally: Yeah, because Orion, it's, uh, got the very
00:29:57 --> 00:29:59 distinctive three stars in a row. And it's
00:29:59 --> 00:30:00 got those two other bright stars I mentioned
00:30:00 --> 00:30:02 right here on Betelgeuse. So it is very, very
00:30:02 --> 00:30:04 easy to spot. And it's right on the celestial
00:30:04 --> 00:30:06 equator too. So once you see it, you know,
00:30:06 --> 00:30:08 you know what your orientation is. With the
00:30:08 --> 00:30:10 Orion Nebula, the pictures you see in
00:30:10 --> 00:30:12 magazines and books and on the Internet and
00:30:12 --> 00:30:14 everything, they're taken by electronic
00:30:14 --> 00:30:16 cameras these days that can bring out
00:30:16 --> 00:30:17 fantastic colour and fantastic detail. Uh,
00:30:17 --> 00:30:19 you don't get that with the naked eye. You
00:30:19 --> 00:30:21 don't get that looking through a telescope
00:30:21 --> 00:30:22 either, unless you've got a Whopper
00:30:22 --> 00:30:24 telescope, which most people don't. These
00:30:24 --> 00:30:25 things just generally look like a bit of a
00:30:25 --> 00:30:28 smudge of light. So. But you can see this
00:30:28 --> 00:30:30 Orion Nebula as a smudge of light just with
00:30:30 --> 00:30:31 the unaided eye, if you've got dark enough
00:30:31 --> 00:30:33 sky conditions. And when you look up, you
00:30:33 --> 00:30:35 think, well, that's actually Orion Nebula and
00:30:35 --> 00:30:36 that's that thing. I've seen a big picture in
00:30:36 --> 00:30:39 a book that is amazing. But it's about 1500
00:30:39 --> 00:30:40 light years or so away, a little bit less.
00:30:41 --> 00:30:43 It's quite amazing. And it's a massive star
00:30:43 --> 00:30:46 cloud where new solar systems are being born.
00:30:46 --> 00:30:48 So it's wonderful when you look up and see
00:30:48 --> 00:30:50 something and you realise what you're seeing.
00:30:50 --> 00:30:52 Even if it might not look impressive, it's
00:30:52 --> 00:30:54 impressive because you can see it makes any
00:30:54 --> 00:30:55 sense. And of course, getting a pair of
00:30:55 --> 00:30:57 binoculars or a telescope under the Orion
00:30:57 --> 00:30:59 Nebula makes it look a whole lot better. Now,
00:30:59 --> 00:31:01 above the northeastern, uh, horizon that time
00:31:01 --> 00:31:03 in the morning again, we've got Taurus
00:31:03 --> 00:31:05 constellation. Taurus. And it's got these
00:31:05 --> 00:31:07 star clusters known as the Hyades and the
00:31:07 --> 00:31:08 Pleiades. We talk about the Pleiades all the
00:31:08 --> 00:31:10 time. It's the Seven Sisters. They look
00:31:10 --> 00:31:12 fantastic through binoculars. Just a pair of
00:31:12 --> 00:31:13 binoculars. You don't need a telescope. Just
00:31:13 --> 00:31:15 get some binoculars onto them and they'll
00:31:15 --> 00:31:16 become a lot easier to see. Uh, over the next
00:31:16 --> 00:31:18 couple of months, as I described, they start
00:31:18 --> 00:31:20 to rise higher and then get into the evening
00:31:20 --> 00:31:22 sty rather than the Morning star. Now let's
00:31:22 --> 00:31:23 turn to the planets. There are three of them
00:31:23 --> 00:31:25 on show just after sunset. So if you take a
00:31:25 --> 00:31:27 look to the west, you'll see Mercury and
00:31:27 --> 00:31:30 Venus. Mercury is the smaller, dimmer of the
00:31:30 --> 00:31:32 two lower down in the sky. Venus is the big
00:31:32 --> 00:31:34 bright one higher up. Now, as the days go by,
00:31:34 --> 00:31:36 in the first week and a half, couple of weeks
00:31:36 --> 00:31:38 of October, you'll see Venus will be dropping
00:31:38 --> 00:31:40 down lower each night down towards the
00:31:40 --> 00:31:42 horizon, while Mercury is actually rising
00:31:42 --> 00:31:44 higher up. And they'll pass each other on the
00:31:44 --> 00:31:45 8th, on the evening of the 8th, so they'll be
00:31:45 --> 00:31:48 roughly the same distance above the horizon,
00:31:48 --> 00:31:49 sort of next to each other. Then a few days
00:31:49 --> 00:31:52 later, on the 12th, the moon will make an
00:31:52 --> 00:31:53 appearance. It'll be joining in because the
00:31:53 --> 00:31:55 Moon travels through the sky night after
00:31:55 --> 00:31:57 night, sort of moves along night after night.
00:31:57 --> 00:31:59 So it eventually, um, sidles up to these two
00:31:59 --> 00:32:02 planets on the 12th, making a close triangle
00:32:02 --> 00:32:04 with them. That should be really nice to see.
00:32:04 --> 00:32:05 I'm going to get out and have a look at that
00:32:05 --> 00:32:06 one on the other side of the sky in the
00:32:06 --> 00:32:08 evening we've got Saturn, which is low above
00:32:08 --> 00:32:09 the eastern horizon.
00:32:09 --> 00:32:11 After sunset, give it an hour or two to rise
00:32:11 --> 00:32:14 up out of any murk or obstacles that might be
00:32:14 --> 00:32:15 on your horizon and then have a look. It's
00:32:15 --> 00:32:17 always best to have a look at planets when
00:32:17 --> 00:32:19 they're as high as they can get in the night
00:32:19 --> 00:32:21 sky. Saturn just looks like a, uh, fairly
00:32:21 --> 00:32:24 bright yellowish star to the unaided eye. But
00:32:24 --> 00:32:26 you get a small telescope onto it and you'll
00:32:26 --> 00:32:28 see that it's this giant ringed planet with
00:32:28 --> 00:32:30 these amazing rings going around it. Although
00:32:30 --> 00:32:32 at the moment they are a bit edge on towards
00:32:32 --> 00:32:34 us, so they don't look as great as they do at
00:32:34 --> 00:32:35 other times when the rings are sort of more
00:32:35 --> 00:32:37 angled towards us. But Saturn always
00:32:37 --> 00:32:38 impresses everyone when they see it through a
00:32:38 --> 00:32:40 telescope. It's impressive the first time and
00:32:40 --> 00:32:42 it's impressive every time after that. It's
00:32:42 --> 00:32:44 really, it's one of those things, if you show
00:32:44 --> 00:32:46 someone Saturn through a telescope for the
00:32:46 --> 00:32:48 first time, they'll gasp. They go like that.
00:32:48 --> 00:32:50 It's involuntary. People say that is really
00:32:50 --> 00:32:52 Saturn. It looks like what it looks like in
00:32:52 --> 00:32:54 the pictures. Not often you can get that sort
00:32:54 --> 00:32:55 of thing, um, when you look through a
00:32:55 --> 00:32:57 telescope for the other two bright planets,
00:32:57 --> 00:32:58 Jupiter and Mars, again, you're going to have
00:32:58 --> 00:33:00 to be up very late, a night owl, or you're
00:33:00 --> 00:33:02 going to have to wake up early before dawn
00:33:02 --> 00:33:04 because they both rise over the northeastern
00:33:04 --> 00:33:05 horizon a bit after 4 o' clock in the
00:33:05 --> 00:33:07 morning, just as with Saturn. Give these two
00:33:07 --> 00:33:09 planets an hour or so to rise up out of the
00:33:09 --> 00:33:11 murk down into the horizon and you get a
00:33:11 --> 00:33:13 better view. But don't leave it too long, of
00:33:13 --> 00:33:14 course, because dawn will be just around the
00:33:14 --> 00:33:17 corner. Mars doesn't look like much through a
00:33:17 --> 00:33:19 telescope. It's a fairly small planet a long
00:33:19 --> 00:33:21 way away. Um, you can see that it's a planet.
00:33:21 --> 00:33:23 Doesn't look like a star. You can actually
00:33:23 --> 00:33:24 see that it's a disc of a planet, but it's
00:33:24 --> 00:33:27 pretty small. Jupiter on the other hand, is
00:33:27 --> 00:33:29 very, very impressive, really impressive.
00:33:29 --> 00:33:30 Through a telescope you should be able to
00:33:30 --> 00:33:33 make out some sort of band structure in its
00:33:33 --> 00:33:35 clouds, its cloud system. We can't see any
00:33:35 --> 00:33:37 surface, we just see the clouds. Uh, and it's
00:33:37 --> 00:33:39 got these sort of equatorial bands and sort
00:33:39 --> 00:33:42 of middle bands towards the poles. So it's
00:33:42 --> 00:33:44 got a structured sort of cloud system. You
00:33:44 --> 00:33:45 also should be able to make out several of
00:33:45 --> 00:33:48 its largest moons. They just look like tiny
00:33:48 --> 00:33:49 bright pinpricks of light. There are four of
00:33:49 --> 00:33:51 them that are, ah, fairly easy to see. You
00:33:51 --> 00:33:53 can even see them with binoculars. They don't
00:33:53 --> 00:33:54 look like pictures you would see of the moon,
00:33:54 --> 00:33:56 they just look like tiny pinpricks of light.
00:33:56 --> 00:33:58 But if you go out night after night and have
00:33:58 --> 00:33:59 a look, you'll see that they've moved as they
00:33:59 --> 00:34:01 go around the planet very quickly. And
00:34:01 --> 00:34:03 sometimes you might see two on one side and
00:34:03 --> 00:34:05 two on the other side. Some might see three
00:34:05 --> 00:34:06 on one side and one on the other side.
00:34:06 --> 00:34:08 Sometimes you might only see two or three.
00:34:08 --> 00:34:09 You think, where are the other ones gone?
00:34:09 --> 00:34:11 Well, they're probably around behind Jupiter
00:34:11 --> 00:34:13 or they could be in Jupiter's shadow if
00:34:13 --> 00:34:15 they're not directly behind. So that's really
00:34:15 --> 00:34:17 fascinating to see if you want to see what
00:34:17 --> 00:34:20 Galileo saw, which is what helped start off
00:34:20 --> 00:34:21 scientific revolution.
00:34:21 --> 00:34:23 Stuart Gary: Yeah, but looking at Jupiter got Galileo in a
00:34:23 --> 00:34:24 lot of trouble.
00:34:25 --> 00:34:26 Jonathan Nally: Well, you won't get into trouble these days.
00:34:26 --> 00:34:27 You won't be put under house arrest or
00:34:27 --> 00:34:29 anything. If you go out and have a look at
00:34:29 --> 00:34:31 Jupiter, See, back in his days before the
00:34:31 --> 00:34:32 telescope was around, when people looked up,
00:34:32 --> 00:34:34 they could just see that there were the stars
00:34:34 --> 00:34:36 which never changed position. And there are
00:34:36 --> 00:34:39 these planets, planets from the Greek word
00:34:39 --> 00:34:41 meaning wanderers, that, um, move along the
00:34:41 --> 00:34:43 night sky in predictable paths. And people
00:34:43 --> 00:34:45 have known about them for thousands of years.
00:34:45 --> 00:34:47 And that was it. That's all we knew about the
00:34:47 --> 00:34:47 night sky.
00:34:47 --> 00:34:49 And of course there were all these
00:34:49 --> 00:34:51 mythological things about, you know, that the
00:34:51 --> 00:34:54 heavens being perfect, you know, unchanging
00:34:54 --> 00:34:56 perfect, and, uh, it was all God's plan sort
00:34:56 --> 00:34:58 of thing. And, and the Earth was in the
00:34:58 --> 00:35:00 centre of the universe and Earth was special
00:35:00 --> 00:35:01 and everything was supposed to go around the
00:35:01 --> 00:35:03 Earth, which we now of course know is not
00:35:03 --> 00:35:05 right. But when Galileo look at Jupiter and
00:35:05 --> 00:35:07 he saw these little moons and night after
00:35:07 --> 00:35:08 night he saw that their position changed, he
00:35:08 --> 00:35:10 thought, aha, uh-huh, they must be moon,
00:35:10 --> 00:35:12 that's a planet and it must have its own
00:35:12 --> 00:35:14 moons going around it. So things aren't as
00:35:14 --> 00:35:17 perfect as we thought they were. There are
00:35:17 --> 00:35:19 other places out there that seem to be like
00:35:19 --> 00:35:21 Earth and that sort of kicked off, kicked off
00:35:21 --> 00:35:23 the whole scientific revolution and aren't,
00:35:23 --> 00:35:25 uh, we glad that it did. But anyway, if you
00:35:25 --> 00:35:27 get a chance to have a look at Jupiter
00:35:27 --> 00:35:28 through a small telescope, if you know
00:35:28 --> 00:35:30 someone who's got a scope, if you don't have
00:35:30 --> 00:35:32 one yourself, really do take the opportunity
00:35:32 --> 00:35:34 because it's quite an amazing site. And that,
00:35:34 --> 00:35:35 Stuart, is for sky for October.
00:35:35 --> 00:35:37 Stuart Gary: That's senior science writer and sky and
00:35:37 --> 00:35:39 Telescope magazine contributor Jonathan
00:35:39 --> 00:35:41 Nally. And this is Space Time.
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