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In this episode of SpaceTime, we delve into groundbreaking advancements in our understanding of gravity, the intriguing thermal characteristics of the Moon, and the discovery of white dwarf pulsars.
A New Theory of Gravity
Scientists have proposed a revolutionary new theory of gravity that brings us closer to the long-sought theory of everything. This quantum theory of gravity aims to unify gravity with the fundamental forces of nature, offering potential solutions to some of the most profound questions in physics, including the nature of dark matter and dark energy. We explore the implications of this theory and how it could reshape our understanding of the universe's origins and the behavior of black holes.
The Moon's Hot Side
Recent findings suggest that the Moon's near side is significantly hotter than its far side, with temperatures reaching up to 170 degrees Celsius higher. This research, based on data from NASA's GRAIL mission, reveals how geological differences between the lunar sides could be attributed to thermal variations in the Moon's mantle. We discuss the potential for these methods to enhance our understanding of other celestial bodies, including Mars and the moons of Jupiter and Saturn.
White Dwarf Pulsars: A Stellar Discovery
Astronomers have made a remarkable discovery of a white dwarf star that emits radio pulses, challenging the notion that only neutron stars can produce such signals. This discovery, reported in Nature Astronomy, opens up new avenues for understanding pulsar mechanisms and their sources across the Milky Way. We examine the significance of this finding and what it means for our knowledge of stellar evolution.
www.spacetimewithstuartgary.com
✍️ Episode References
Reports on Progress in Physics
https://iopscience.iop.org/journal/0034-4885
Nature
https://www.nature.com/nature/
Nature Astronomy
https://www.nature.com/natureastronomy/
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00:00 This is Space Time Series 28, Episode 65 for broadcast on 30 May 2025
01:00 New theory of gravity
12:15 The Moon's thermal characteristics
22:30 Discovery of white dwarf pulsars
30:00 Skywatch: June night skies and the Taurids meteor shower
00:00:00 --> 00:00:02 Stuart Gary: This is space Time Series 28, Episode
00:00:02 --> 00:00:05 65 for broadcast on 30 May
00:00:05 --> 00:00:08 2025. Coming up on SpaceTime,
00:00:08 --> 00:00:11 a new theory of gravity which brings the long sought
00:00:11 --> 00:00:13 after theory of everything closer to reality.
00:00:14 --> 00:00:17 Is there a hot side to the moon? And
00:00:17 --> 00:00:20 astronomers discover white dwarf pulsars for
00:00:20 --> 00:00:23 the first time. All that and more coming up
00:00:23 --> 00:00:24 on, Space Time.
00:00:25 --> 00:00:28 Voice Over Guy: Welcome to Space Time with Stuart
00:00:28 --> 00:00:28 Gary
00:00:45 --> 00:00:48 Stuart Gary: Scientists have developed a new theory of gravity which
00:00:48 --> 00:00:51 brings the long sought after theory of everything just
00:00:51 --> 00:00:54 a little bit closer to reality. A quantum
00:00:54 --> 00:00:57 theory of gravity would clear the path to answering some of
00:00:57 --> 00:01:00 the biggest questions in physics. The study
00:01:00 --> 00:01:03 detailed in the journal Reports on progress in Physics
00:01:03 --> 00:01:06 claims a unified theory combining gravity with the other
00:01:06 --> 00:01:09 fundamental forces of nature. That's electromagnetism and
00:01:09 --> 00:01:11 the strong and weak nuclear forces may well at long
00:01:11 --> 00:01:14 last be within reach. Bringing
00:01:14 --> 00:01:17 gravity into the fold has been the goal of generations
00:01:17 --> 00:01:20 of physicists who have struggled to reconcile the
00:01:20 --> 00:01:23 incompatibility of the two cornerstones of modern physics,
00:01:23 --> 00:01:25 namely quantum field theory and Albert
00:01:25 --> 00:01:28 Einstein's theory of general relativity. The
00:01:28 --> 00:01:31 key has been developing a new quantum theory of
00:01:31 --> 00:01:33 gravity, which describes gravity in ways
00:01:33 --> 00:01:36 compatible with the standard model of particle physics, the
00:01:36 --> 00:01:38 cornerstone of our understanding of the universe.
00:01:39 --> 00:01:41 And in the process, it's opening the door to an
00:01:41 --> 00:01:44 improved understanding of how the universe began.
00:01:45 --> 00:01:48 While the world of theoretical physics may seem remote from
00:01:48 --> 00:01:51 applicable technology, the findings are remarkable.
00:01:51 --> 00:01:54 See, modern technology is built on fundamental advances.
00:01:55 --> 00:01:58 For example, the GPS in your smartphone works
00:01:58 --> 00:02:01 thanks to Albert Einstein's theory of gravity. The
00:02:01 --> 00:02:04 study's authors, Miko Partanen and Giulka Tutti, both
00:02:04 --> 00:02:07 from Aalto University, say that within a few years their new
00:02:07 --> 00:02:09 hypothesis may well unlock, crucial
00:02:09 --> 00:02:12 understanding. If, it does turn out to lead to a
00:02:12 --> 00:02:15 complete quantum field theory of gravity, then eventually it
00:02:15 --> 00:02:17 will give answers to the very difficult problems of
00:02:17 --> 00:02:20 understanding singularities at the centre of black holes
00:02:21 --> 00:02:24 and even understanding the Big bang of creation itself.
00:02:24 --> 00:02:27 However, we're not there yet. Some fundamental
00:02:27 --> 00:02:30 questions of physics still remain under this so called theory
00:02:30 --> 00:02:33 of Everything. For example, current theories still can't
00:02:33 --> 00:02:35 explain why there's more matter than antimatter in the
00:02:35 --> 00:02:38 observable universe. And they still don't know what
00:02:38 --> 00:02:40 dark energy and what dark matter really are.
00:02:41 --> 00:02:44 The key to this new hypothesis was finding a way to
00:02:44 --> 00:02:46 describe gravity in a suitable gauge theory,
00:02:46 --> 00:02:49 A a kind of theory in which particles interact with each other through
00:02:49 --> 00:02:52 a field. The most familiar gauge field is
00:02:52 --> 00:02:55 the electromagnetic field. Talkey says that when
00:02:55 --> 00:02:58 electrically charged particles interact with each other, they interact
00:02:58 --> 00:03:01 through the electromagnetic Field, which is the pertinent
00:03:01 --> 00:03:04 gauge field. So when particles have energy, the
00:03:04 --> 00:03:07 interactions they have, just because they have energy would happen
00:03:07 --> 00:03:10 through the gravitational field. But a, challenge
00:03:10 --> 00:03:12 long facing physicists is finding a gauge theory
00:03:12 --> 00:03:15 for gravity, one that's compatible with the gauge theories
00:03:15 --> 00:03:18 of the other three fundamental forces, the electromagnetic force,
00:03:19 --> 00:03:22 weak nuclear force, and the strong nuclear force. The
00:03:22 --> 00:03:24 standard model of particle physics is itself a gauge
00:03:24 --> 00:03:27 theory which describes those three forces and has
00:03:27 --> 00:03:30 certain symmetries. The Tennant says the
00:03:30 --> 00:03:33 main idea is to have a gravity gauge theory with
00:03:33 --> 00:03:36 a symmetry that's similar to the standard model symmetries,
00:03:36 --> 00:03:39 instead of basing the theory on the very different kind
00:03:39 --> 00:03:41 of spacetime symmetry involved in Einstein's
00:03:41 --> 00:03:44 general relativity. Without such a hypothesis,
00:03:44 --> 00:03:47 physicists couldn't reconcile our two most powerful
00:03:47 --> 00:03:50 theories, quantum field theory and general relativity.
00:03:50 --> 00:03:53 Quantum field theory describes the world of the very
00:03:53 --> 00:03:56 small, tiny particles interacting in probabilistic
00:03:56 --> 00:03:59 ways. On the other hand, general relativity
00:03:59 --> 00:04:02 describes the grand physics of the cosmic world, the
00:04:02 --> 00:04:05 universe as a whole. So they're both descriptions of
00:04:05 --> 00:04:07 our, universe, but from very different perspectives.
00:04:08 --> 00:04:10 And both theories have been confirmed with extraordinary precision,
00:04:10 --> 00:04:13 yet they're still incompatible with each other. And because
00:04:13 --> 00:04:16 gravitational directions are weak, more precision is needed
00:04:16 --> 00:04:19 in order to study true quantum gravity effects beyond general
00:04:19 --> 00:04:22 relativity. Patanan says a quantum theory
00:04:22 --> 00:04:25 of gravity is needed in order to understand what kind of phenomena
00:04:25 --> 00:04:28 there are in cases where there's a gravitational field with
00:04:28 --> 00:04:31 high energies, the sort of conditions you'd find around black
00:04:31 --> 00:04:34 holes and very early in the universe's existence,
00:04:34 --> 00:04:37 just after the Big Bang. And they're the sort of
00:04:37 --> 00:04:39 places where existing theories of physics all stop
00:04:39 --> 00:04:42 working. Although the hypothesis is promising,
00:04:42 --> 00:04:45 the authors point out they've not yet completed its
00:04:45 --> 00:04:48 proof. It uses a technical procedure
00:04:48 --> 00:04:51 known as renormalization. That's a mathematical way of
00:04:51 --> 00:04:54 dealing with the infinities that show up in the calculations.
00:04:54 --> 00:04:57 So far, the authors have shown that while this works up to a
00:04:57 --> 00:05:00 certain point for so called first order terms, they're yet
00:05:00 --> 00:05:03 to make sure that these infinities can be eliminated throughout the
00:05:03 --> 00:05:06 entire calculation. You see, if renormalization
00:05:06 --> 00:05:09 doesn't work for higher order terms, you'll get infinite results.
00:05:09 --> 00:05:11 So it's vital to show that this renormalization
00:05:12 --> 00:05:14 continues to work, and therefore they still need to
00:05:14 --> 00:05:17 make a complete proof. Nevertheless, it's
00:05:17 --> 00:05:20 fascinating work. This is space time.
00:05:21 --> 00:05:24 Still to come, is there a hot side to the moon?
00:05:24 --> 00:05:27 And astronomers discover their first white dwarf
00:05:27 --> 00:05:30 pulsars? All that and more still to come on,
00:05:30 --> 00:05:31 spacetime.
00:05:39 --> 00:05:40 Jonathan Nally: Foreign.
00:05:47 --> 00:05:50 Stuart Gary: Claims. The Moon's near Earth facing side is actually
00:05:50 --> 00:05:53 hotter than its far side. The findings reported
00:05:53 --> 00:05:56 in the journal Nature, based on data from NASA's GRAIL
00:05:56 --> 00:05:59 spacecraft and the twin Ebb and Flow spacecraft, which have
00:05:59 --> 00:06:02 been studying the Moon from orbit. Our Moon is
00:06:02 --> 00:06:04 gravitationally tidally locked to the Earth. That
00:06:04 --> 00:06:07 means the same side always faces our planet.
00:06:07 --> 00:06:10 Even more fascinating is the dichotomy of the Moon,
00:06:10 --> 00:06:13 which has long intrigued scientists. You see, there
00:06:13 --> 00:06:15 are notable differences in geology,
00:06:16 --> 00:06:18 volcanism and crustal thickness between the
00:06:18 --> 00:06:21 lunar near and far sides. The Moon's near
00:06:21 --> 00:06:24 side appears darker and it's dominated by smooth
00:06:24 --> 00:06:27 ancient lava flows, indicating a high concentration
00:06:27 --> 00:06:30 of volcanism. On the other hand, the far side
00:06:30 --> 00:06:33 is far more rugged. The new study using data from
00:06:33 --> 00:06:35 Grail suggests that this dichotomy is caused by a 2
00:06:35 --> 00:06:38 to 3% difference in the lunar mantle's ability to
00:06:38 --> 00:06:41 deform on each side. The authors suggest
00:06:41 --> 00:06:44 that the reason is that the Moon's near side mantle
00:06:44 --> 00:06:47 is up to 170 degrees Celsius hotter than its
00:06:47 --> 00:06:50 far side. It's thought this thermal difference could be
00:06:50 --> 00:06:53 caused by the radioactive decay of thorium and titanium within
00:06:53 --> 00:06:55 the Moon's near side, which could be a remnant of the
00:06:55 --> 00:06:58 volcanic activity that formed the near side surface between
00:06:58 --> 00:07:01 3 and 4 billion years ago. The authors say
00:07:01 --> 00:07:04 the same methods which have now been used to study the Moon's
00:07:04 --> 00:07:07 interior from orbit could also be used to measure differences in
00:07:07 --> 00:07:10 the structure of other planetary bodies, such as the Red planet
00:07:10 --> 00:07:12 Mars, the Saturn moon Enceladus and the
00:07:12 --> 00:07:15 Jovian moon Ganymede. This is space
00:07:15 --> 00:07:18 time still to come. Astronomers discover
00:07:18 --> 00:07:21 a white dwarf star acting like a pulsar and the
00:07:21 --> 00:07:24 June solstice. The constellation Sagittarius
00:07:24 --> 00:07:27 and the Taurids meteor shower are among the
00:07:27 --> 00:07:29 highlights of the June night skies on Skywatch.
00:07:44 --> 00:07:47 A white dwarf and a red dwarf have been discovered closely
00:07:47 --> 00:07:50 orbiting each other and emitting radio pulses every two hours.
00:07:51 --> 00:07:54 The findings, reported in the journal Nature Astronomy, mean
00:07:54 --> 00:07:57 that neutron stars are no longer the only stellar
00:07:57 --> 00:07:59 bodies that emit such pulses. a key
00:07:59 --> 00:08:02 factor in this discovery could be the way the binary
00:08:02 --> 00:08:05 pair is spaced unusually far apart from each other.
00:08:06 --> 00:08:09 Thanks to follow up observations using optical and X ray telescopes,
00:08:09 --> 00:08:11 the study's authors were able to determine the origin of these
00:08:11 --> 00:08:14 pulsars coming from this binary system with
00:08:14 --> 00:08:16 certainty. The findings are important because they're
00:08:16 --> 00:08:19 helping to explain the sources of these strange radio emissions which
00:08:19 --> 00:08:22 are found right across the Milky Way Galaxy.
00:08:22 --> 00:08:24 This is space, time
00:08:40 --> 00:08:43 and time. Now to check out the night skies of Dune on
00:08:43 --> 00:08:46 Skywatch June is the fourth month of
00:08:46 --> 00:08:49 the old Roman calendar. It's named after Juno, who was
00:08:49 --> 00:08:51 the wife of Jupiter, is also the equivalent to the Greek goddess
00:08:51 --> 00:08:54 Hera. Another belief is that the month's name
00:08:54 --> 00:08:57 actually comes from the Latin word juniors, which means
00:08:57 --> 00:09:00 younger ones. It's a great time to look up
00:09:00 --> 00:09:03 the night skies and marvel at the majesty of the Milky
00:09:03 --> 00:09:06 Way as it puts on its spectacular overhead
00:09:06 --> 00:09:08 display. June also marks the winter
00:09:08 --> 00:09:11 solstice in the Southern Hemisphere, which this year happens at
00:09:11 --> 00:09:14 12:42 in the afternoon of Saturday, June
00:09:14 --> 00:09:16 21, Australian Eastern Standard Time.
00:09:17 --> 00:09:20 That's 10:42 in the evening of Friday, June 20,
00:09:20 --> 00:09:23 US Eastern Daylight Time, and 2:42 in the
00:09:23 --> 00:09:26 morning of Saturday, June 21, Greenwich Mean Time.
00:09:26 --> 00:09:29 and while it means the start of winter south of the equator, it means
00:09:29 --> 00:09:32 the arrival of summer for our lucky listeners in the northern
00:09:32 --> 00:09:35 part of the planet. The June solstice occurs when
00:09:35 --> 00:09:38 the sun reaches its most northerly point in the sky as
00:09:38 --> 00:09:41 seen from Earth zenith, appearing to be directly above
00:09:41 --> 00:09:44 the Tropic of Cancer. See, Earth's
00:09:44 --> 00:09:46 seasons are governed by the tilt of the planet's axis
00:09:46 --> 00:09:49 as it journeys around the Sun. Now, the Earth's
00:09:49 --> 00:09:51 axis is always pointing the same direction in space,
00:09:52 --> 00:09:55 regardless of the position of the planet Earth as it orbits around
00:09:55 --> 00:09:58 the Sun. So on the day of the June solstice,
00:09:58 --> 00:10:00 Earth's, south pole is tilted by 23.5 degrees away
00:10:00 --> 00:10:03 from the sun, while the North Pole is tilted by the same
00:10:03 --> 00:10:06 amount towards the Sun. The sun rising in the
00:10:06 --> 00:10:09 northeast and setting in the northwest. Of course,
00:10:09 --> 00:10:12 six months later, when the South Pole is tilted towards the sun,
00:10:12 --> 00:10:15 it's the Southern hemisphere summer. And in between,
00:10:15 --> 00:10:17 we have the autumn and spring equinoxes.
00:10:18 --> 00:10:21 Temperatures on Earth aren't determined by Earth's orbital
00:10:21 --> 00:10:24 distance from the sun, but rather the angle of the Sun's
00:10:24 --> 00:10:26 rays striking the Earth. So in summer,
00:10:26 --> 00:10:29 the Sun's high in the sky and the rays hit the planet at
00:10:29 --> 00:10:32 a steep angle. In winter, the Sun's lower in the
00:10:32 --> 00:10:35 sky and the rays strike the Earth at a far shallower
00:10:35 --> 00:10:38 angle. Now, in most parts of the world, the
00:10:38 --> 00:10:40 seasons begin on the day of the solstice, or
00:10:40 --> 00:10:43 equinox. However, Australia is weird.
00:10:43 --> 00:10:46 Here, seasons begin on the first day of a specific
00:10:46 --> 00:10:48 calendar month. That means the 1st of March for autumn, the
00:10:48 --> 00:10:51 1st of June for winter, the 1st of September for spring,
00:10:51 --> 00:10:54 and you guessed it, the 1st of December for summer.
00:10:55 --> 00:10:58 Okay, let's check out the stars. Well, almost
00:10:58 --> 00:11:01 overhead this time of the year, we find the constellation
00:11:01 --> 00:11:04 Virgo Virgo is named after the
00:11:04 --> 00:11:06 goddess of justice and the harvest in ancient Greek mythology,
00:11:06 --> 00:11:09 who used her scales to weigh good and evil.
00:11:09 --> 00:11:12 However, she became so disenchanted with the evil deeds of men,
00:11:12 --> 00:11:15 she wound up throwing away her scales and retreated to the
00:11:15 --> 00:11:18 heavens. interestingly, the ancient Egyptians
00:11:18 --> 00:11:21 also associate Virgo, with agriculture. There she was
00:11:21 --> 00:11:24 the goddess Isis who sprinkled the heads of wheat across
00:11:24 --> 00:11:26 the sky, forming the Milky Way. To
00:11:26 --> 00:11:29 science, Virgo is a tightly packed region
00:11:29 --> 00:11:31 containing some 2 galaxies, all
00:11:31 --> 00:11:34 gravitationally bound into a giant galaxy cluster
00:11:34 --> 00:11:37 some 60 million light years away. In
00:11:37 --> 00:11:40 fact, our own Local Group of galaxies, dominated by the
00:11:40 --> 00:11:43 Milky Way and Andromeda, are outlying members of this
00:11:43 --> 00:11:46 group. The Virgo Cluster is at the heart
00:11:46 --> 00:11:49 of what's known as the Virgo Supercluster, a massive
00:11:49 --> 00:11:52 galactic node in the large scale cosmic web. Like
00:11:52 --> 00:11:55 str of the universe, the mass of the Virgo
00:11:55 --> 00:11:58 Supercluster is so great that its gravity generates the
00:11:58 --> 00:12:00 Virgo centric flow, causing our Milky Way galaxy
00:12:00 --> 00:12:03 as well as Andromeda and all the other members of the local galactic
00:12:03 --> 00:12:06 group to move towards the supercluster at around 400
00:12:06 --> 00:12:09 kilometers per second. That's despite the accelerating
00:12:09 --> 00:12:12 expansion of the universe over cosmic timescales.
00:12:12 --> 00:12:15 The Virgo Supercluster is now thought to be a lobe on
00:12:15 --> 00:12:18 an even larger galactic supercluster called
00:12:18 --> 00:12:21 Laniakea, the center of which is known as the
00:12:21 --> 00:12:24 Great Attractor. despite the Virgo Cluster's size, it's
00:12:24 --> 00:12:27 so far away from us it's hard to see without a decently sized
00:12:27 --> 00:12:29 backyard telescope. You'll need something at least 100
00:12:29 --> 00:12:32 mm in diameter or larger in order to see it.
00:12:33 --> 00:12:36 Now, if you look directly straight up at zenith, you'll see
00:12:36 --> 00:12:39 the constellation Corvus the crow. Greek
00:12:39 --> 00:12:41 mythology tells us that Corvus could talk to humans,
00:12:41 --> 00:12:44 but he was a lazy bird. And so
00:12:44 --> 00:12:47 Apollo took away his ability to speak and banished
00:12:47 --> 00:12:49 into the heavens. One of the most
00:12:49 --> 00:12:52 spectacular highlights of the constellations Virgo and
00:12:52 --> 00:12:55 Corvus is the Spectacular Sombrero
00:12:55 --> 00:12:58 Galaxy M104. Visible with a good
00:12:58 --> 00:13:01 pair of binoculars or a small backout telescope, this
00:13:01 --> 00:13:04 stunning spiral galaxy is seen almost edge on, and
00:13:04 --> 00:13:07 it will provide you with a spectacular backlit view of its
00:13:07 --> 00:13:09 galactic bold stars and the molecular gas and dust
00:13:09 --> 00:13:12 leans in its arms. M
00:13:12 --> 00:13:15 M104 is located some 31 million light
00:13:15 --> 00:13:18 years away, and it's moving away from the Milky way at about
00:13:18 --> 00:13:21 1 kilometers per second. A light year
00:13:21 --> 00:13:23 is about 10 trillion kilometers, the distance a
00:13:23 --> 00:13:26 photon can travel in a year. At the speed of light, which is about
00:13:26 --> 00:13:29 300 kilometers per second in a vacuum and the
00:13:29 --> 00:13:32 ultimate speed limit of the universe. The
00:13:32 --> 00:13:35 Sombrero Galaxy has a diameter of around 50
00:13:35 --> 00:13:38 light years, making it about 30% the size of
00:13:38 --> 00:13:40 our Milky Way galaxy. It's surrounded by up to
00:13:40 --> 00:13:43 2 globular clusters. And it has an active
00:13:43 --> 00:13:46 central supermassive black hole at least a billion times
00:13:46 --> 00:13:49 the mass of our Sun. Now, by comparison,
00:13:49 --> 00:13:52 Sagittarius A, that's the supermassive black hole at the
00:13:52 --> 00:13:55 center of our own galaxy, has just 4.3 million times
00:13:55 --> 00:13:58 the Sun's mass. Globular clusters are
00:13:58 --> 00:14:00 either the central remnants of smaller galaxies
00:14:00 --> 00:14:03 cannibalized by larger ones, or, alternatively,
00:14:03 --> 00:14:06 they're tight balls comprising millions of
00:14:06 --> 00:14:08 stars, which all originally formed at the same time in
00:14:08 --> 00:14:11 the same collapsing molecular gas and dust cloud.
00:14:12 --> 00:14:15 By the way, the brightest star in Virgo is Spica, a
00:14:15 --> 00:14:18 spectroscopic binary located some 250 light years
00:14:18 --> 00:14:20 away. Spectroscopic binaries are
00:14:20 --> 00:14:23 stars that are orbiting so close together they can only be told
00:14:23 --> 00:14:26 apart by their individual spectrographic signatures.
00:14:27 --> 00:14:30 Now, looking about 20 degrees above the western horizon early
00:14:30 --> 00:14:33 in the evening this time of the year, you'll find the fourth brightest
00:14:33 --> 00:14:36 object in the sky, the dog star, Sirius.
00:14:36 --> 00:14:39 Only the sun, the Moon, and the planet Venus look
00:14:39 --> 00:14:42 brighter. Looking to the northwest or
00:14:42 --> 00:14:44 right of Sirius, you'll find another fairly bright
00:14:44 --> 00:14:47 star, Procyon, the brightest star in Canis
00:14:47 --> 00:14:50 Minor, the Lesser Dog. In Greek
00:14:50 --> 00:14:52 mythology, Canis Major and Canis Minor were
00:14:52 --> 00:14:55 Orion's hunting dogs. Procyon is a
00:14:55 --> 00:14:58 binary star system. It comprises a
00:14:58 --> 00:15:01 spectral type F main sequence white yellow star
00:15:01 --> 00:15:04 Procyon A and a faint white dwarf companion,
00:15:04 --> 00:15:07 Procyon B. Main sequence stars are
00:15:07 --> 00:15:09 those undergoing hydrogen fusion into helium in their
00:15:09 --> 00:15:12 cores. Astronomers describe stars in
00:15:12 --> 00:15:15 terms of spectral types, a classification system based
00:15:15 --> 00:15:18 on temperature and characteristics. The hottest,
00:15:18 --> 00:15:21 most massive, and most luminous stars are known as spectral
00:15:21 --> 00:15:24 type O blue stars. They're followed by
00:15:24 --> 00:15:27 spectral type B blue white stars. Then spectral
00:15:27 --> 00:15:29 type A white stars, spectral type F
00:15:29 --> 00:15:32 whiteish yellow stars, spectral type G yellow
00:15:32 --> 00:15:35 stars. That's where our sun fits in. Then there's spectral
00:15:35 --> 00:15:38 type K orange stars. And the coolest and least massive
00:15:38 --> 00:15:41 known stars are spectral type M red stars.
00:15:42 --> 00:15:45 Each spectral classification can also be subdivided using
00:15:45 --> 00:15:47 a numeric digit to represent temperature, with zero
00:15:47 --> 00:15:50 being the hottest and nine the coolest. And then
00:15:50 --> 00:15:53 you can add a Roman numeral to represent luminosity.
00:15:54 --> 00:15:56 Put all that together and our sun is officially
00:15:56 --> 00:15:59 classified as the G2V or G25
00:15:59 --> 00:16:02 yellow dwarf star. Also included
00:16:02 --> 00:16:05 in the stellar classification system are spectral types
00:16:05 --> 00:16:08 L, T and Y which are assigned to failed
00:16:08 --> 00:16:11 stars known as brown dwarves, some of which were born as
00:16:11 --> 00:16:14 spectral type M red stars but became brown dwarfs
00:16:14 --> 00:16:17 after losing some of their mass. Brown dwarves
00:16:17 --> 00:16:19 fit into a unique category between the largest planets which
00:16:19 --> 00:16:22 can be up to 13 times the Mass of say Jupiter, and the smallest
00:16:22 --> 00:16:25 spectro type M red dwarf stars which are around
00:16:25 --> 00:16:28 75 to 80 times the mass of Jupiter or around
00:16:28 --> 00:16:30 0.08 solar masses.
00:16:30 --> 00:16:33 Now the other type of star we just mentioned were white dwarves.
00:16:34 --> 00:16:37 There the stellar corpses of sun like stars.
00:16:37 --> 00:16:40 Having used up all its nuclear fuel supply fusing hydrogen
00:16:40 --> 00:16:43 into helium, these stars expand into red
00:16:43 --> 00:16:46 giants as they fuse helium into carbon and oxygen.
00:16:46 --> 00:16:49 The sun and stars like it aren't massive enough
00:16:49 --> 00:16:51 to fuse carbon and oxygen into heavier elements
00:16:52 --> 00:16:55 and so they turn off. Eventually the outer
00:16:55 --> 00:16:58 gaseous envelopes will float off into space as spectacular
00:16:58 --> 00:17:00 objects known as planetary nebula. What's
00:17:00 --> 00:17:03 left behind is a super dense white hot stellar
00:17:03 --> 00:17:06 core A about the size of the Earth. This is
00:17:06 --> 00:17:09 the white dwarf which will slowly cool over the
00:17:09 --> 00:17:12 eons. The white dwarf Procyon
00:17:12 --> 00:17:15 b is about 0.6 times the mass of the
00:17:15 --> 00:17:17 sun and has a diameter of around 8
00:17:17 --> 00:17:20 km. Located about
00:17:20 --> 00:17:22 11.6 light years away, Procyon A is about
00:17:22 --> 00:17:25 1.5 times the mass and twice the radius of our Sun.
00:17:26 --> 00:17:28 But it also has some seven times the Sun's
00:17:28 --> 00:17:31 luminosity. That makes it unusually bright for a star
00:17:31 --> 00:17:34 of this type of and that suggests that it's now starting
00:17:34 --> 00:17:37 to evolve off the main sequence, having fused
00:17:37 --> 00:17:39 nearly all of its core hydrogen into helium.
00:17:40 --> 00:17:43 So that means it's slowly expanding out to become a
00:17:43 --> 00:17:46 subgiant as it begins fusing its core helium
00:17:46 --> 00:17:48 into oxygen and carbon and burning hydrogen
00:17:48 --> 00:17:51 further out from the core. As it continues to
00:17:51 --> 00:17:54 expand, the star will eventually swirl to somewhere
00:17:54 --> 00:17:57 between 80 and 150 times its current diameter, in
00:17:57 --> 00:18:00 the process becoming a red or orange giant.
00:18:00 --> 00:18:03 This will probably happen within the next 10 to 100 million
00:18:03 --> 00:18:06 years. The two stars Procyon A and
00:18:06 --> 00:18:09 B orbit each other every 40.82 Earth years at
00:18:09 --> 00:18:12 an average distance of 15 astronomical units, about
00:18:12 --> 00:18:15 the distance Uranus is from the Sun. An
00:18:15 --> 00:18:18 astronomical unit is the average distance between the Earth and the
00:18:18 --> 00:18:20 sun which is around 150 million kilometers or
00:18:20 --> 00:18:23 8.3 light minutes. Now looking
00:18:23 --> 00:18:26 towards the north northwest right now and you'll see the
00:18:26 --> 00:18:29 constellation Leo the Lion, looking like a bunch of stars
00:18:29 --> 00:18:31 shaped like an upside down question mark.
00:18:32 --> 00:18:35 Located just 36.7 light years away.
00:18:35 --> 00:18:38 Arcturus is a bloated, aging red giant
00:18:38 --> 00:18:41 about 7.1 billion years old and nearing the
00:18:41 --> 00:18:44 end of its life. Having used up all its
00:18:44 --> 00:18:47 core hydrogen, it's now fusing helium into carbon
00:18:47 --> 00:18:50 and oxygen. This has caused the star, which
00:18:50 --> 00:18:53 is only slightly more massive than our sun, to expand out
00:18:53 --> 00:18:56 to around 25 times the sun's diameter, in the
00:18:56 --> 00:18:58 process becoming about 170 times as luminous.
00:18:59 --> 00:19:02 It will soon puff off its outer gaseous envelope as a
00:19:02 --> 00:19:05 planetary nebula, revealing its white hot stellar core.
00:19:06 --> 00:19:09 In Greek mythology, Arcturus was the guardian
00:19:09 --> 00:19:12 of the bear. This is a reference to it being next
00:19:12 --> 00:19:14 to the constellations Ursa Major and Ursa Minor, the
00:19:14 --> 00:19:17 greater and lesser bears. There's some
00:19:17 --> 00:19:20 indications that Arcturus could have a binary stellar
00:19:20 --> 00:19:22 companion, but the results remain inconclusive.
00:19:23 --> 00:19:26 There's also some speculation that it could have a large planet
00:19:26 --> 00:19:28 or substellar object around 12 Jupiter masses
00:19:28 --> 00:19:31 orbiting it. that's close to brown dwarf size. But
00:19:31 --> 00:19:34 again, the search remains inconclusive.
00:19:35 --> 00:19:37 To the east are the three brightest stars in the
00:19:37 --> 00:19:40 constellation Libra, the scales of Justice. They are
00:19:40 --> 00:19:43 visible about halfway about 40 degrees above the
00:19:43 --> 00:19:45 horizon. These represent the claws of
00:19:45 --> 00:19:48 Scorpius the Scorpion, which is chasing Orion across
00:19:48 --> 00:19:51 the sky. The brightest star in the constellation
00:19:51 --> 00:19:53 Scorpius is Alphascorpi or
00:19:53 --> 00:19:55 Antares, the Scorpion's Heart.
00:19:56 --> 00:19:59 Easily seen with the unaided eye, this red supergiant
00:19:59 --> 00:20:02 is some 550 light years away and it's one of the
00:20:02 --> 00:20:05 largest known stars in the universe. It has about
00:20:05 --> 00:20:08 18 times the mass and 883 times
00:20:08 --> 00:20:11 the diameter of our sun. And it has some 10
00:20:11 --> 00:20:13 times more luminosity than our Sun.
00:20:14 --> 00:20:17 Looking to the southeast now and you'll see the constellation
00:20:17 --> 00:20:20 Sagittarius the Archer. Sagittarius
00:20:20 --> 00:20:23 marks the direction of the center of our galaxy, the Milky way.
00:20:23 --> 00:20:26 It's located 26 light years away and is home to
00:20:26 --> 00:20:29 the galaxy's supermassive black hole, Sagittarius
00:20:29 --> 00:20:32 A. To the ancient Babylonians,
00:20:32 --> 00:20:35 Sagittarius was the God Nurgle the Centaur,
00:20:35 --> 00:20:37 a creature that was half man and half horse.
00:20:38 --> 00:20:41 By the time Greek mythology took over, Sagittarius was
00:20:41 --> 00:20:43 carrying his bow loaded with an arrow pointing towards
00:20:43 --> 00:20:46 Antares, the heart of Scorpius the Scorpion,
00:20:47 --> 00:20:50 the center of the Milky Way Galaxy and its supermassive
00:20:50 --> 00:20:52 black hole, Sagittarius a lie in the
00:20:52 --> 00:20:55 westernmost part of the constellation Sagittarius.
00:20:56 --> 00:20:58 One of the brightest stars in Sagittarius is Alpha
00:20:58 --> 00:21:01 Sagittari, or Rock Bat, meaning the Archer's Knee,
00:21:01 --> 00:21:03 a spectral type B blue star
00:21:03 --> 00:21:06 located 182 light years away. It is some
00:21:06 --> 00:21:09 2.5 times the diameter of the sun and it's about 40
00:21:09 --> 00:21:12 times as luminous. Astronomers think it's
00:21:12 --> 00:21:15 surrounded by a dense debris disk and a newborn companion
00:21:15 --> 00:21:17 star which is only just joining the main sequence.
00:21:18 --> 00:21:21 the overall brightest star in Sagittarius or Cas
00:21:21 --> 00:21:23 Australis, the southern part of the Bow,
00:21:23 --> 00:21:26 Epsilon Sagittaria is a binary star system
00:21:26 --> 00:21:29 located 143 light years away. The
00:21:29 --> 00:21:32 primary star is an evolved spectra type B blue giant.
00:21:32 --> 00:21:35 Now at the end of its life on the main sequence, it
00:21:35 --> 00:21:38 has about three and a half times the Sun's mass, almost
00:21:38 --> 00:21:40 seven times its radius, and it's radiating around
00:21:40 --> 00:21:43 363 times the Sun's
00:21:43 --> 00:21:45 luminosity. It's also a very strong X
00:21:45 --> 00:21:48 ray source, and it's spinning incredibly rapidly with an
00:21:48 --> 00:21:51 estimated radial velocity of some 236
00:21:51 --> 00:21:54 kilometers per second. The system also
00:21:54 --> 00:21:57 displays an excess of infrared radiation emissions,
00:21:57 --> 00:22:00 suggesting the presence of a circumstellar disk of dust.
00:22:00 --> 00:22:03 The second star in the system appears to be inside
00:22:03 --> 00:22:06 this debris disk. Astronomers are
00:22:06 --> 00:22:09 speculating that this may well develop into a spectral type
00:22:09 --> 00:22:12 G yellow dwarf star with about 95% of our
00:22:12 --> 00:22:14 Sun's mass. Sigma Sagittarius
00:22:15 --> 00:22:17 is the constellation's second brightest star. we know the name
00:22:17 --> 00:22:20 Nunci has Babylonian origins. However, its
00:22:20 --> 00:22:23 meaning remains a mystery. It is thought to represent
00:22:23 --> 00:22:26 the ancient Babylonian city of Urdu on the Euphrates
00:22:26 --> 00:22:29 River. If correct, that would make Nunqui the
00:22:29 --> 00:22:31 oldest known star name currently in use.
00:22:32 --> 00:22:35 It's a spectral type B blue star located
00:22:35 --> 00:22:37 about 260 light years away. It has about
00:22:37 --> 00:22:40 8 times the Sun's mass, about 4.5 times its
00:22:40 --> 00:22:43 radius, and some 3 times the
00:22:43 --> 00:22:46 luminosity of our Sun. Zeta Sagittaria, or
00:22:46 --> 00:22:49 a cell at the armpit, is a binary star system
00:22:49 --> 00:22:51 88 light years away from the Sun. It's
00:22:51 --> 00:22:54 currently speeding away from the solar system, but, may once have been
00:22:54 --> 00:22:57 as near as 1.5 light years from the sun about 1.4 million
00:22:57 --> 00:23:00 years ago. And that would make it a former close
00:23:00 --> 00:23:03 neighbor. One of the stars in the system is a
00:23:03 --> 00:23:06 spectrotype, a white giant, while the other is a spectre
00:23:06 --> 00:23:08 type a white supergiant, the pair orbiting each other
00:23:08 --> 00:23:11 every 21 Earth years. The system's
00:23:11 --> 00:23:14 combined mass is thought to be 5.26
00:23:14 --> 00:23:17 times the mass of our Sun. Delta Sagittarius
00:23:17 --> 00:23:19 appears to be a double star system located around
00:23:19 --> 00:23:22 348 light years away and listed is an
00:23:22 --> 00:23:25 orange giant. Then there's Eta
00:23:25 --> 00:23:27 Sagittaria, another double star system, this one located
00:23:27 --> 00:23:30 146 light years from Earth. the primary star
00:23:30 --> 00:23:33 in the system is an aging, bloated red giant
00:23:33 --> 00:23:36 on the asentopic giant branch. That means it's
00:23:36 --> 00:23:39 no longer fusing hydrogen or helium at its core and is
00:23:39 --> 00:23:42 instead fusing heavier elements, burning hydrogen
00:23:42 --> 00:23:45 and helium in the shell. It's already expanded out
00:23:45 --> 00:23:48 to some 57 times the radius of our sun and
00:23:48 --> 00:23:51 is now nearing the end of its life. The second
00:23:51 --> 00:23:54 star in the system is the spectral type F main sequence
00:23:54 --> 00:23:56 white yellow dwarf, which appears to be in a binary system with
00:23:56 --> 00:23:58 the primary star orbiting it every
00:23:58 --> 00:24:01 1270 Earth years. PI
00:24:01 --> 00:24:04 Sagittarius, or Ibalda, is a triple star system
00:24:04 --> 00:24:07 located 510 light years away. The
00:24:07 --> 00:24:10 primary star in the system appears to be a spectral type
00:24:10 --> 00:24:13 F white yellow giant, which has exhausted its core
00:24:13 --> 00:24:16 hydrogen and so is now off the main sequence and evolving
00:24:16 --> 00:24:18 into a red giant. We know PI
00:24:18 --> 00:24:21 Sagittarius has two nearby companions, but little
00:24:21 --> 00:24:24 is known about either of them. Beta Sagittaria, or,
00:24:24 --> 00:24:27 Arcap, the Achilles tendon is the designation shared by two
00:24:27 --> 00:24:29 separate star systems. One's about
00:24:29 --> 00:24:31 378 light years from Earth, the other
00:24:31 --> 00:24:34 139 light years away. Beta
00:24:34 --> 00:24:36 Sagittary A is a spectral type B blue dwarf star,
00:24:36 --> 00:24:39 while Beta Sagittarius B is a white yellow giant.
00:24:40 --> 00:24:42 Lying nearly at the very center of the constellation
00:24:42 --> 00:24:45 Sagittarius is Nova Sagittari, which was
00:24:45 --> 00:24:48 only discovered in 2015. And as its name
00:24:48 --> 00:24:51 suggests, Rest is a nova, a white dwarf in a binary
00:24:51 --> 00:24:54 system with another star, which is constantly drawing material
00:24:54 --> 00:24:57 off its companion. Now, once enough material
00:24:57 --> 00:24:59 reaches the surface of the white dwarf, this added mass
00:24:59 --> 00:25:02 triggers a thermonuclear explosion, causing the star
00:25:02 --> 00:25:05 to suddenly light up like a beacon and then slowly
00:25:05 --> 00:25:08 begin fading again over the following weeks and
00:25:08 --> 00:25:11 months. Now, this blast isn't strong enough to destroy
00:25:11 --> 00:25:14 the white dwarf, only the additional material that it's picked up.
00:25:14 --> 00:25:17 And with this additional material now burnt off, the same cycle
00:25:17 --> 00:25:20 can start over again, and the process can repeat itself
00:25:20 --> 00:25:23 on time scales ranging from every few years to tens of
00:25:23 --> 00:25:26 thousands of years apart. The
00:25:26 --> 00:25:29 Sagittarius constellation also hosts many star
00:25:29 --> 00:25:31 clusters and nebulae, including some of the best known
00:25:31 --> 00:25:34 astronomical objects in the sky. These
00:25:34 --> 00:25:37 include the lagoon Nebula, Messier 8, a
00:25:37 --> 00:25:40 spectacular Pinker Mission Nebula located 8 light
00:25:40 --> 00:25:43 years away, which measures 140 light years by
00:25:43 --> 00:25:46 60 light years across the central area of the
00:25:46 --> 00:25:49 Lagoon Nebula is also known as the Hourglass Nebula
00:25:49 --> 00:25:52 because of its distinctive shape. The shape is caused
00:25:52 --> 00:25:55 by matter propelled by a massive star forming in a region
00:25:55 --> 00:25:57 known as Herschel 36. One of the few star forming
00:25:57 --> 00:26:00 nebulae that's possible to see with the unaided eye,
00:26:00 --> 00:26:03 the Lagoon Nebula was instrumental in the discovery of what
00:26:03 --> 00:26:06 are known as Bok globules, more than 17
00:26:06 --> 00:26:08 of which have now been found in the nebula.
00:26:08 --> 00:26:11 Astronomers believe Bok Globules contain
00:26:11 --> 00:26:14 embryonic protostars destined to eventually become
00:26:14 --> 00:26:15 new stellar generations.
00:26:17 --> 00:26:19 Probably the best known nebula in Sagittarius is
00:26:19 --> 00:26:22 Messier 17, the Horsehead Nebula.
00:26:22 --> 00:26:25 It's located 4 light years
00:26:25 --> 00:26:28 away and is a dense region of ionized atomic
00:26:28 --> 00:26:31 hydrogen. Also known as the Omega, or
00:26:31 --> 00:26:33 Swan Nebula. It spans some 15 light years in
00:26:33 --> 00:26:36 diameter and has some 800 times the mass of our Sun.
00:26:37 --> 00:26:40 it's considered one of the brightest and most massive star forming
00:26:40 --> 00:26:43 regions in our galaxy with a geometry very similar to the
00:26:43 --> 00:26:46 Orion Nebula, except that it's viewed edge on rather
00:26:46 --> 00:26:48 than face on. The open star cluster
00:26:48 --> 00:26:51 NGC6618 is embedded within
00:26:51 --> 00:26:54 the nebulosity and it causes the gases of the nebula to
00:26:54 --> 00:26:57 shine due to intense radiation from these hot young
00:26:57 --> 00:27:00 stars. Open star clusters are loosely
00:27:00 --> 00:27:03 bound groups of a few thousand stars, which were originally
00:27:03 --> 00:27:06 all formed in the same molecular gas and dust cloud, but are
00:27:06 --> 00:27:09 not as tightly bonded together as the stars in globular
00:27:09 --> 00:27:11 clusters. It's thought open clusters generally
00:27:11 --> 00:27:14 survive for a few hundred million years, with the most massive
00:27:14 --> 00:27:17 ones surviving for maybe a few billion years.
00:27:17 --> 00:27:20 In contrast, the more massive globular clusters exert
00:27:20 --> 00:27:23 far stronger gravitational attraction to their members,
00:27:23 --> 00:27:26 and they therefore can survive much longer in cosmic
00:27:26 --> 00:27:28 time. The nebula is thought to contain over
00:27:28 --> 00:27:31 800 stars, including more than 100 of the
00:27:31 --> 00:27:34 largest, most massive spectral type OMB blue
00:27:34 --> 00:27:36 stars. More than a thousand
00:27:36 --> 00:27:39 additional stars are now being formed in the surrounding
00:27:39 --> 00:27:42 molecular gas and dust clouds. It's also one of the
00:27:42 --> 00:27:45 youngest known clusters in the galaxy, with an age of just a million
00:27:45 --> 00:27:48 years. The cloud of interstellar material
00:27:48 --> 00:27:51 forming the Nebula is roughly 40 light years in
00:27:51 --> 00:27:53 diameter, and it's thought to contain some 30 solar
00:27:53 --> 00:27:56 masses. Another famous
00:27:56 --> 00:27:59 nebulosity is the Trifid Nebula, Messier 20.
00:27:59 --> 00:28:02 It's another large star forming a mission Nebula
00:28:02 --> 00:28:04 containing many very young hot stars.
00:28:05 --> 00:28:08 Located somewhere between 2 and 9 light years from Earth,
00:28:08 --> 00:28:11 the Trifid Nebula has a diameter of around 50 light
00:28:11 --> 00:28:14 years. Now, the outside of the Trifid Nebula is
00:28:14 --> 00:28:16 a bluish reflection Nebula, while the inner region is
00:28:16 --> 00:28:19 glowing pink thanks to ionized hydrogen. There
00:28:19 --> 00:28:22 are two dark bands dividing the Trifid Nebula into
00:28:22 --> 00:28:25 three regions or lobes. Hydrogen in the
00:28:25 --> 00:28:28 nebula is being ionized by a central triple star system
00:28:28 --> 00:28:31 which formed in the intersection of the two bands
00:28:31 --> 00:28:33 creating the characteristic pink color.
00:28:34 --> 00:28:36 Other star forming regions such as
00:28:36 --> 00:28:39 NGC559, which is located
00:28:39 --> 00:28:41 5 light years from Earth contain both red emission
00:28:41 --> 00:28:43 and blue reflection regions.
00:28:44 --> 00:28:47 This grouping of the Lagoon Nebula, the Trifid
00:28:47 --> 00:28:49 Nebula and NGC 6559 is
00:28:49 --> 00:28:51 known as the Sagittarius triplet.
00:28:52 --> 00:28:55 Another spectacular sight in Sagittarius is the red
00:28:55 --> 00:28:57 Spider Nebula NGC
00:28:57 --> 00:29:00 6537. It's a planetary
00:29:00 --> 00:29:03 nebula some 8 light years from Earth. It
00:29:03 --> 00:29:06 is a prominent two lobe shape. this could be due to
00:29:06 --> 00:29:09 a binary companion or possibly magnetic fields and has
00:29:09 --> 00:29:12 an S shaped symmetry with the lobes opposite each other appearing
00:29:12 --> 00:29:14 similar. The central white dwarf
00:29:14 --> 00:29:17 remnant, the original star produces a powerful
00:29:17 --> 00:29:20 10 degree hot 3 kilometers per
00:29:20 --> 00:29:22 second stellar wind. And that wind is generating
00:29:22 --> 00:29:25 100 billion kilometer high waves of
00:29:25 --> 00:29:28 supersonic shocks which are formed as local gas is
00:29:28 --> 00:29:30 being compressed and heated in front of the rapidly expand
00:29:31 --> 00:29:34 lobes. Atoms caught in the shock front are
00:29:34 --> 00:29:37 radiating invisible light, giving the nebula its unique
00:29:37 --> 00:29:39 spider like shape and also contributing to its
00:29:39 --> 00:29:42 expansion. The star at the center of the Red Spider
00:29:42 --> 00:29:45 Nebula is shrouded by a dust shell, making its exact
00:29:45 --> 00:29:48 properties hard to determine. We think it has a
00:29:48 --> 00:29:50 surface temperature of around 25 degrees,
00:29:50 --> 00:29:53 although temperatures of up to half a million degrees can't be ruled
00:29:53 --> 00:29:56 out, which would make it one of the hottest white dwarf stars
00:29:56 --> 00:29:59 known as Now if you look directly south
00:29:59 --> 00:30:01 this time of year, you'll find the star Polaris
00:30:01 --> 00:30:04 Australis or more accurately Sigma Octanus,
00:30:04 --> 00:30:07 the nearest star to the southern celestial pole and
00:30:07 --> 00:30:10 consequently the counterpart to the north star Polaris.
00:30:11 --> 00:30:13 However, Sigma Octanus is much harder to see than
00:30:13 --> 00:30:16 Polaris because it's much fainter. Located
00:30:16 --> 00:30:19 some 270 light years away, it's now an orange
00:30:19 --> 00:30:21 giant nearing the end of its life.
00:30:22 --> 00:30:25 Turning to the southwest just above the horizon and we
00:30:25 --> 00:30:28 find Canopus, the second brightest star in the night sky
00:30:28 --> 00:30:30 after Sirius Aureus. It's located some
00:30:30 --> 00:30:33 310 light years away and is the brightest star in the
00:30:33 --> 00:30:36 constellation Carina, the Keel. Canopus
00:30:36 --> 00:30:39 is a supergiant some nine times the mass of the
00:30:39 --> 00:30:41 sun and some 71 times its diameter.
00:30:42 --> 00:30:45 The month of June also marks the first of two
00:30:45 --> 00:30:48 annual encounters with the Taureds meteor shower.
00:30:48 --> 00:30:51 The Taureds are generated as the Earth passes through a debris
00:30:51 --> 00:30:54 stream left by the Comet 2P anke, which
00:30:54 --> 00:30:56 itself could be pieces of a much larger comet that broke
00:30:56 --> 00:30:59 apart around 20 to 30 years ago, most
00:30:59 --> 00:31:02 likely following numerous interactions with the powerful gravitational
00:31:02 --> 00:31:05 field of the planet Jupiter. As their name
00:31:05 --> 00:31:08 suggests, the Taurids radiant or apparent point of
00:31:08 --> 00:31:11 origin is in the constellation Taurus the Bull.
00:31:11 --> 00:31:14 The Taurid's meteor shower is made up of larger, more
00:31:14 --> 00:31:16 massive material. Think of pebbles instead of dust
00:31:16 --> 00:31:19 grains. Earth, passes through this stream twice
00:31:19 --> 00:31:22 every year, once in June, then again in October when
00:31:22 --> 00:31:24 they're referred to as Halloween fireballs. The
00:31:24 --> 00:31:27 Taurids release material both by normal cometary
00:31:27 --> 00:31:30 activity and occasionally through close encounters with the
00:31:30 --> 00:31:33 gravitational tidal forces exerted by the Earth and other
00:31:33 --> 00:31:36 planets. And all this makes the Taured
00:31:36 --> 00:31:38 stream of material the largest in the inner solar system.
00:31:39 --> 00:31:42 Now, since this meteor stream is rather spread out in space,
00:31:42 --> 00:31:45 planet Earth takes several weeks to pass through it, causing an
00:31:45 --> 00:31:48 extended period of meteor activity compared with the much smaller
00:31:48 --> 00:31:50 periods of activity by other meteor showers.
00:31:51 --> 00:31:54 Now included in the Turret stream is a denser flow of
00:31:54 --> 00:31:57 gravelly meteors called the Turret Swarm. And they're
00:31:57 --> 00:31:59 thought to be a ribbon of rocks roughly 75 million
00:31:59 --> 00:32:02 km by 150 km across and held
00:32:02 --> 00:32:05 in orbit by Jupiter's gravity. Now,
00:32:05 --> 00:32:07 occasionally planet Earth passes through the larger
00:32:07 --> 00:32:10 meteors in this denser Taurid swarm.
00:32:10 --> 00:32:13 And one of the larger chunks in the Taurid swarm is now thought
00:32:13 --> 00:32:16 to have caused the infamous Tunguska event in the skies
00:32:16 --> 00:32:18 above Siberia on June 30,
00:32:18 --> 00:32:21 1908. The Tunguska event is now believed
00:32:21 --> 00:32:24 to have been the airburst of a 100 meter wide meteor
00:32:24 --> 00:32:27 in the skies above the Tunguska region of Russia, resulting
00:32:27 --> 00:32:30 in mass Devastation over a 2 square
00:32:30 --> 00:32:33 kilometer region of forest, turning trees into
00:32:33 --> 00:32:36 matchsticks. In fact, the blast was so
00:32:36 --> 00:32:39 bright it lit up the night sky in London a third of the
00:32:39 --> 00:32:41 way around the planet. The Tunguska event
00:32:41 --> 00:32:44 remains the largest known Earth impact event of a
00:32:44 --> 00:32:46 meteor in recorded modern times.
00:32:47 --> 00:32:50 It's always been considered to be a one in a thousand year event,
00:32:50 --> 00:32:52 assuming a random distribution of events over time.
00:32:53 --> 00:32:56 But there's a problem with that because of these new studies suggesting the
00:32:56 --> 00:32:59 event may have been caused by a Taurid swarm meteor. And
00:32:59 --> 00:33:02 with the Earth passing through the Taurid swarm periodically, it
00:33:02 --> 00:33:05 changes the odds considerably. If, this new study
00:33:05 --> 00:33:08 is correct, the swarm heightens the possibility of a cluster
00:33:08 --> 00:33:10 of large impacts on Earth over a short period of time.
00:33:11 --> 00:33:14 further complicating matters, the dune Taurids are actually
00:33:14 --> 00:33:17 two separate showers. The southern Taurids
00:33:17 --> 00:33:20 are associated with the comet 2P ANKI, while the northern
00:33:20 --> 00:33:22 taurids originate from the asteroid 2004
00:33:23 --> 00:33:25 TG10 at concentric kilometer wide
00:33:25 --> 00:33:28 asteroid classified as a near Earth object and a potentially
00:33:28 --> 00:33:31 hazardous asteroid of the Apollo group. Something to
00:33:31 --> 00:33:34 think about. Joining us now for the rest of
00:33:34 --> 00:33:37 our tour of the night skies of June is science editor
00:33:37 --> 00:33:38 Jonathan Nally.
00:33:38 --> 00:33:38 Jonathan Nally: G' day, Stuart Gary.
00:33:38 --> 00:33:41 Yeah, well, it's June, so June evenings start off with the
00:33:41 --> 00:33:44 constellation Orion low in the west. So
00:33:44 --> 00:33:47 Orion's one of our favorite constellations, isn't it? I love Orion. Everyone
00:33:47 --> 00:33:50 loves Orion. That's very easily recognizable. But it is low
00:33:50 --> 00:33:53 in the west, after sunset. And as the Earth
00:33:53 --> 00:33:56 turns during the evening, it dips below the horizon
00:33:56 --> 00:33:59 pretty quickly. And by the middle of the month, it's actually going to be gone after
00:33:59 --> 00:34:02 sunset. You won't be able to see it anymore. But it will reappear
00:34:02 --> 00:34:04 towards the end of the year in the eastern sky. And that, when Orion
00:34:04 --> 00:34:07 appears in the eastern star at the end of the year, that's when you know that for people
00:34:07 --> 00:34:10 in the Southern hemisphere, summer is arriving. Or for people in the
00:34:10 --> 00:34:13 Northern Hemisphere, they know that winter is arriving. So it's a good
00:34:13 --> 00:34:16 sign post the old Orion. But yeah, you get your last glimpse of it now
00:34:16 --> 00:34:18 basically in the evening, the first half of June.
00:34:18 --> 00:34:21 Also in the western part of the sky, there are two bright stars.
00:34:21 --> 00:34:24 One's called Sirius, the other one's called Procyon.
00:34:24 --> 00:34:27 Sirius is the brightest star in the night sky.
00:34:27 --> 00:34:30 Procyon is the eighth brightest, still very bright.
00:34:30 --> 00:34:32 And they have a few similarities, actually. They're both binary
00:34:32 --> 00:34:35 stars. And each of them is a, what they call a main
00:34:35 --> 00:34:38 sequence, a normal sort of star with a white dwarf going around it, a
00:34:38 --> 00:34:41 white dwarf star. And they're both within constellations that
00:34:41 --> 00:34:44 have the word dog in the name. Sirius is in the
00:34:44 --> 00:34:47 constellation Canis Major, or the Greater Dog. And
00:34:47 --> 00:34:50 Procyon is in the constellation Canis Minor, or
00:34:50 --> 00:34:50 the Lesser Dog.
00:34:51 --> 00:34:54 In the southwest, there's another bright star, Canopus. Canopus
00:34:54 --> 00:34:56 is my favorite star in the whole sky. I reckon it's the second brightest
00:34:56 --> 00:34:59 star in the night sky, about half as bright as Sirius. You
00:34:59 --> 00:35:02 only get a really good look of it. And look at it if you're in the southern hemisphere
00:35:02 --> 00:35:05 from people in the Northern hemisphere, sort of lower latitude, you
00:35:05 --> 00:35:08 can see it, certain times of the year. But, from down here, it's
00:35:08 --> 00:35:09 pretty much visible all the time.
00:35:09 --> 00:35:12 Stuart Gary: And it's actually the most luminous star in our neighborhood. It's
00:35:12 --> 00:35:13 huge.
00:35:13 --> 00:35:16 Jonathan Nally: Yeah, it is. It's about 10 times brighter than our sun,
00:35:16 --> 00:35:19 about 10 times its size. And fortunately it is
00:35:19 --> 00:35:21 about 310 light years away, which is very close in
00:35:21 --> 00:35:24 space terms. But if it was much closer than 310 light
00:35:24 --> 00:35:27 years away, it would be very, very bright
00:35:27 --> 00:35:30 indeed. I mean, if it was a fraction of that
00:35:30 --> 00:35:32 distance we really wouldn't have a night sky.
00:35:32 --> 00:35:35 Stuart Gary: Is it the case that Canopus was once closer to our
00:35:35 --> 00:35:38 star system than Sirius and then moved away and
00:35:38 --> 00:35:39 it's slowly coming back again?
00:35:39 --> 00:35:42 Jonathan Nally: I think it is the case, yeah. I think it is the case that, the
00:35:42 --> 00:35:45 distances have changed a little bit and Canopus at one point was
00:35:45 --> 00:35:48 brighter than CE Sirius I think. So, you know, we would.
00:35:48 --> 00:35:51 We're moving our solar systems moving through space and Sirius is
00:35:51 --> 00:35:53 moving through space and Canopus is moving through space. So the distances
00:35:53 --> 00:35:56 between each other are moving around a bit. But yeah,
00:35:56 --> 00:35:59 Canopus at the moment is not as bright as Sirius. Sirius is
00:35:59 --> 00:36:02 the brightest star. But you know, you go out to the naked
00:36:02 --> 00:36:05 eye telling one star apart of that
00:36:05 --> 00:36:08 brightness, turning one star apart from another is,
00:36:08 --> 00:36:11 it's not the easiest thing to do if you get a good look
00:36:11 --> 00:36:14 at both and you say, yeah, yeah, well, Sirius is brighter but you know, they
00:36:14 --> 00:36:17 both are very, very bright. But yeah, I don't know, Canopus is just of my
00:36:17 --> 00:36:20 favourites really. I guess because it was one of the first stars I identified when I was a kid
00:36:20 --> 00:36:23 and because it's a nice bright star far down in the Southern Star, we
00:36:23 --> 00:36:25 sort of got it all to ourselves sort of thing. So, it's, it's
00:36:26 --> 00:36:28 just got a sort of a sentimental value for me.
00:36:28 --> 00:36:30 Stuart Gary: We're very lucky in the southern hemisphere, aren't we?
00:36:30 --> 00:36:33 Jonathan Nally: Oh, ah, we're super lucky in the southern hemisphere. We've got lots of bright things. We've
00:36:33 --> 00:36:36 got the, center of the Milky Way galaxy overhead and we've got the
00:36:36 --> 00:36:38 Magellanic Cloud galaxies. There are plenty good things. Which is not to say
00:36:38 --> 00:36:41 that there aren't plenty of great things in the northern sky as well.
00:36:41 --> 00:36:44 But we, we do have a few extras it seems, down here that makes
00:36:44 --> 00:36:47 it a bit special. Now, high in the south, about two thirds of the
00:36:47 --> 00:36:50 up from the horizon, down in the south, you've got the Southern Cross this time of
00:36:50 --> 00:36:53 year and it's standing upright for a change because a lot
00:36:53 --> 00:36:56 of the year it's either upside down or on its left side or on its right side
00:36:56 --> 00:36:59 or whatever. But roundabout now, it's pretty Much standing
00:36:59 --> 00:37:02 upright. Nearby you've got the pair of stars
00:37:02 --> 00:37:05 known as the two Pointers, Alpha and Beta Centauri.
00:37:05 --> 00:37:08 We talk about those a lot on the show. The Milky Way runs
00:37:08 --> 00:37:11 right through this region of the Cross. It's sort of heading from east to west across
00:37:11 --> 00:37:14 the sky. And there are plenty of star clusters and nebulae for
00:37:14 --> 00:37:16 amateur astronomers to enjoy looking along its length even
00:37:16 --> 00:37:19 with a pair of binoculars. With a telescope it's great, particularly if you've got
00:37:19 --> 00:37:22 one that gives you a wide field of view. But just binoculars looks
00:37:22 --> 00:37:25 really superb along there. You do need dark skies though.
00:37:25 --> 00:37:28 City skies do make it very, very hard with all the
00:37:28 --> 00:37:31 light pollution. Now if you do have really dark skies and you've got a
00:37:31 --> 00:37:34 clear southern horizon, you might be able to see two smudges
00:37:34 --> 00:37:37 of light above the southern horizon. And those are these Magellanic Clouds I
00:37:37 --> 00:37:40 was talking about earlier. These are small, odd shaped
00:37:40 --> 00:37:42 galaxies that are very close to the Milky Way. They're the
00:37:42 --> 00:37:45 nearest sizeable galaxies to our own. And you can see them
00:37:45 --> 00:37:48 just with the naked. If you've got dark skies and you let your eyes
00:37:48 --> 00:37:51 get adapted into the dark, they just look like clouds. They look
00:37:51 --> 00:37:54 like tiny clouds. Hence their name, Magellanic Clouds.
00:37:54 --> 00:37:57 There's actually a bit of a push on to rename
00:37:57 --> 00:38:00 them. Do away with the name Magellan because, you
00:38:00 --> 00:38:02 know, in keeping with the way things are these days, you know, Mr.
00:38:02 --> 00:38:05 Magellan, or at least the voyage that he was on, was not too
00:38:05 --> 00:38:08 kind to some of the people and places that they
00:38:08 --> 00:38:11 visited on their around the world trip. So, in the spirit
00:38:11 --> 00:38:14 of that, some people are trying to have those clouds
00:38:14 --> 00:38:16 renamed Spawn, large milky clouds or something along that line sort of
00:38:16 --> 00:38:19 similar to the Milky Way. So we'll see how far that gets
00:38:19 --> 00:38:22 in the northern half of the sky as seen from the southern hemisphere at
00:38:22 --> 00:38:25 least. It does seem a bit bare this time of year. But there is the bright star
00:38:25 --> 00:38:28 Arcturus, which you can see about halfway up from the
00:38:28 --> 00:38:31 northern horizon. And got another bright star that's reasonably
00:38:31 --> 00:38:34 overhead from the latitude of St Sydney. That star is called
00:38:34 --> 00:38:36 Spica. And as the night goes on you'll see that things have
00:38:36 --> 00:38:39 changed because the Earth is rotating by midnight.
00:38:39 --> 00:38:42 Sirius has already set in the west, the brightest star has
00:38:42 --> 00:38:45 already set in the west. And a couple of other bright stars have appeared in the
00:38:45 --> 00:38:48 north. You've got Vega and Altair, which are very famous
00:38:48 --> 00:38:51 stars. They appear in lots of science fiction and TV
00:38:51 --> 00:38:54 series and those sort of things. And there's another star in the southeast
00:38:54 --> 00:38:57 actually another 1m very far in the southeast down the southern
00:38:57 --> 00:39:00 sky. It's one of these ones that you see really only from the southern hemisphere.
00:39:00 --> 00:39:02 It's called Achenar. And that's actually another one of my
00:39:02 --> 00:39:05 favorite stars. Again, probably just because it's sort of special because
00:39:05 --> 00:39:08 it's only visible from the south. And the Milky Way,
00:39:08 --> 00:39:11 which was stretching, as I said, was stretching east west sort of horizontally
00:39:11 --> 00:39:14 across the sky. It's now stretching from the northeast to the
00:39:14 --> 00:39:17 southwest sort of diagonally across the sky. That's just because the
00:39:17 --> 00:39:20 Earth is turning and we get a different perspective now, turning to
00:39:20 --> 00:39:23 the planets. What have we got? Well, we've got Jupiter at the
00:39:23 --> 00:39:26 moment is out of view. It's too close to the sun to be seen.
00:39:26 --> 00:39:29 That'll be that way for a little while. The same goes for Mercury, actually.
00:39:29 --> 00:39:32 Although if you are lucky, and by lucky I mean if you've got a good
00:39:32 --> 00:39:35 clear horizon and there's no buildings and trees and things in the
00:39:35 --> 00:39:38 way, you might just be able to spot Mercury very low above
00:39:38 --> 00:39:40 the western horizon after the sun have set in the last
00:39:40 --> 00:39:43 week or so of June. Other than that, it's,
00:39:43 --> 00:39:46 very, very close to the sun and very hard to see around mid
00:39:46 --> 00:39:49 evening time after it gets dark. Mars can be
00:39:49 --> 00:39:52 seen about halfway up from the horizon very easily. It's a sort
00:39:52 --> 00:39:55 of, it looks like a red star or an orangey
00:39:55 --> 00:39:57 reddish kind of star, as I said, about halfway up
00:39:57 --> 00:40:00 from the horizon to the north if you're viewing from the Southern
00:40:00 --> 00:40:03 Hemisphere or to the south if you're viewing from the Northern Hemisphere.
00:40:04 --> 00:40:06 So see if you can spot that one. You want to spot Saturn,
00:40:07 --> 00:40:10 you have to stay up a bit later. It rises above the Eastern Horizon
00:40:10 --> 00:40:12 about 1:30am at the beginning of the month and by about
00:40:12 --> 00:40:15 midnight at the end of June, which is a bit past
00:40:15 --> 00:40:18 my usual bedtime these days. But if you're out and about late, you should be
00:40:18 --> 00:40:21 able to spot it quite easily. It's fairly bright, has a slightly
00:40:21 --> 00:40:24 yellowish tinge. So it's coming up over the horizon
00:40:24 --> 00:40:26 about 1:30am at the beginning of the month.
00:40:26 --> 00:40:28 And finally we've got Venus, which will also be rising over the
00:40:28 --> 00:40:30 horizon. It follows Saturn, but at around about
00:40:30 --> 00:40:33 3:45am so you have to stay up very, very
00:40:33 --> 00:40:36 late for that one. night owls, will be able to get a view of that.
00:40:37 --> 00:40:39 You can't miss Venus, of course, as I always say is it's so big and
00:40:39 --> 00:40:42 bright, you just can't. It's the third brightest thing in the sky. After the
00:40:42 --> 00:40:45 sun and the moon. So nighttime of course, pretty easy to spot
00:40:45 --> 00:40:46 Venus.
00:40:46 --> 00:40:49 Stuart Gary: You were just coming home from the club at that time, weren't you?
00:40:49 --> 00:40:51 Jonathan Nally: Coming home from the club in my dreams I think. No, I think night
00:40:51 --> 00:40:54 owls, those night shifts and those people getting
00:40:54 --> 00:40:57 up early for morning shifts will be able to spot it. It's one of these things
00:40:57 --> 00:41:00 actually where there are a lot of UFO reports. When people say
00:41:00 --> 00:41:03 get up early in the morning. They're not accustomed to being up early in the morning and
00:41:03 --> 00:41:06 they look out and see this bright white light, doesn't seem to be moving and they
00:41:06 --> 00:41:09 think, oh, it's a ufo. It wasn't there yesterday.
00:41:09 --> 00:41:12 The reality is that it was there yesterday, just didn't notice it. And that's
00:41:12 --> 00:41:15 Venus. Sometimes Venus is visible in the morning sky and
00:41:15 --> 00:41:18 sometimes Venus is visible in the evening sky. And the same
00:41:18 --> 00:41:20 goes for Mercury. So it does tend to move around a little bit.
00:41:20 --> 00:41:23 But there's nothing like a view of Venus. And if you get out,
00:41:23 --> 00:41:26 as we say, if you go bush, you know, get away from the
00:41:26 --> 00:41:29 cities, get away from the city lights and everything. So you get really dark,
00:41:29 --> 00:41:32 dark skies. You know, when Venus is big and bright and
00:41:32 --> 00:41:35 up like that, you know, it throws shadows. It's bright enough to throw
00:41:35 --> 00:41:38 shadows. You can see where you're going just by the light of Venus alone.
00:41:38 --> 00:41:40 It's it's really quite remarkable if you think about Venus. Found
00:41:40 --> 00:41:43 this from a old Isaac Asimov book. Now I don't know whether he
00:41:43 --> 00:41:46 was the first one to come up with this idea or not, but I read it in
00:41:46 --> 00:41:49 ah, an old. Because he used to write science essays and
00:41:49 --> 00:41:52 science columns and science books and things as well as his science
00:41:52 --> 00:41:55 fiction. And he, he said that, you know, because we've got the moon
00:41:55 --> 00:41:58 going around the Earth, right. Which is a fairly big moon
00:41:58 --> 00:42:00 compared to the size of the Earth. Earth moons,
00:42:01 --> 00:42:02 it's a quarter of the.
00:42:02 --> 00:42:03 Stuart Gary: Size of the Earth. It's huge.
00:42:03 --> 00:42:06 Jonathan Nally: Yeah. Some people might call it a double planet system in a way. It's a very
00:42:06 --> 00:42:06 large moon.
00:42:06 --> 00:42:09 Stuart Gary: Just a little bit closer. The barycenter would
00:42:09 --> 00:42:12 be outside the Earth. And under
00:42:12 --> 00:42:15 those circumstances then we would be a binary system like
00:42:15 --> 00:42:15 Pluto and Charon.
00:42:15 --> 00:42:18 Jonathan Nally: That's exactly right. Now that, now what he proposed in this article
00:42:18 --> 00:42:21 was, and this could have changed the course of history actually if this
00:42:21 --> 00:42:24 had happened was that if the moon hadn't formed around
00:42:24 --> 00:42:27 Earth, if instead it had formed in orbit around
00:42:27 --> 00:42:30 Venus. And Venus is about the same size as the Earth.
00:42:30 --> 00:42:33 Then at the distance of Venus. When the moon
00:42:33 --> 00:42:36 was at its furthest from Venus, you would be able to see
00:42:36 --> 00:42:39 just with the unaided eye, you would be able to see Venus
00:42:39 --> 00:42:42 and its moon, theoretical moon, a hypothetical moon
00:42:42 --> 00:42:44 separated from the night sky. And you would see that moon's position
00:42:45 --> 00:42:48 changing from night to night. And you would be drawn to the inescapable
00:42:48 --> 00:42:50 conclusion that that small dot was circling
00:42:51 --> 00:42:54 the larger dot. Right. So something was going around
00:42:54 --> 00:42:56 something else. And of course, remember from our history about things,
00:42:56 --> 00:42:59 you know, working, things going around the Earth, or was the Earth going around the
00:42:59 --> 00:43:02 sun? So the sun going around the Earth. Earth going around the Sun. And for a
00:43:02 --> 00:43:04 long time, of course it was.
00:43:04 --> 00:43:06 Stuart Gary: People had the wrong idea, Galileo and Copernicus before
00:43:06 --> 00:43:07 him.
00:43:07 --> 00:43:10 Jonathan Nally: Yeah, well, see the. You know, it took until Galileo looking
00:43:10 --> 00:43:13 through his telescope to see that the moons were going around Jupiter.
00:43:13 --> 00:43:16 So something else, you know, and yet it moves and something's going
00:43:16 --> 00:43:18 around. Jup. Well, if the moon had formed in
00:43:18 --> 00:43:21 orbit around Venus, then we would have known since
00:43:21 --> 00:43:24 antiquity, you know, since prehistoric
00:43:24 --> 00:43:27 times, that something was going around something else out there in
00:43:27 --> 00:43:30 space. And therefore we would have known that not everything
00:43:30 --> 00:43:33 goes around the Earth, in other words. So this whole idea
00:43:33 --> 00:43:35 that the Earth being the center of everything, which sort of held us back
00:43:35 --> 00:43:38 for a very long time, might not have taken hold,
00:43:38 --> 00:43:41 or at least, not as widely taken hold or for as long
00:43:41 --> 00:43:44 as. So just one of those accidents of nature that the.
00:43:44 --> 00:43:47 The moon formed in orbit around the Earth rather than Venus.
00:43:47 --> 00:43:48 Interesting, isn't it?
00:43:48 --> 00:43:51 Stuart Gary: For a long time, people used to think that because
00:43:51 --> 00:43:54 Venus is covered in clouds and it's a bit closer to the sun
00:43:54 --> 00:43:57 than the Earth, then those clouds must mean lots of rain.
00:43:57 --> 00:44:00 Lots of rain means lots of water on the ground. Lots of water
00:44:00 --> 00:44:03 on the ground means lots of trees could have grown. Lots of
00:44:03 --> 00:44:05 forests. Probably tropical rainforest would have grown there.
00:44:05 --> 00:44:08 Jonathan Nally: Yeah, because Venus is closer to sun, therefore have been warmer. So,
00:44:08 --> 00:44:10 yeah, tropical rainforest and probably dinosaurs.
00:44:11 --> 00:44:13 Stuart Gary: Dinosaurs was the next thing that came up. You're right, yes.
00:44:13 --> 00:44:16 Some scientists even postulated that, well, if you've got tropical
00:44:16 --> 00:44:19 rainforests, you've probably got dinosaurs. How they reached that
00:44:19 --> 00:44:22 conclusion, I don't know, but that was. Yeah, that was very common back in the
00:44:22 --> 00:44:25 50s and 60s. A lot of scientists supported that idea.
00:44:25 --> 00:44:28 Jonathan Nally: It was. It was speculation and I mean, it was sort of a very
00:44:28 --> 00:44:30 uneducated guess, but, you know, we can sort of understand it.
00:44:30 --> 00:44:32 Stuart Gary: Canals on Mars, isn't it?
00:44:32 --> 00:44:34 Jonathan Nally: Yeah, the canals on our sea, the Hensman. It's
00:44:34 --> 00:44:37 hard for people these days, I suppose, to Think
00:44:37 --> 00:44:40 about this. But you go back to the turn of the 19th, 20th
00:44:40 --> 00:44:43 century, go back to the 1900 or whatever, it was
00:44:43 --> 00:44:46 widely assumed that there would be life on the other planets.
00:44:46 --> 00:44:49 Because if there's life on Earth, why wouldn't there be life on other planets?
00:44:49 --> 00:44:52 Because we didn't know what those other planets were like back then. We
00:44:52 --> 00:44:55 didn't have the technology to really establish what
00:44:55 --> 00:44:58 the atmospheres were made of, and you
00:44:58 --> 00:45:00 know, what the temperatures might be, all that sort of, at least without any great
00:45:00 --> 00:45:03 precision. And so even when the first NASA
00:45:03 --> 00:45:06 spacecraft were getting to Mars, it was
00:45:06 --> 00:45:09 still, people were thinking, well, that's going to show things on
00:45:09 --> 00:45:12 Mars, much of vegetation or whatever. But then the first picture
00:45:12 --> 00:45:15 started coming back which just showed a desert world with
00:45:15 --> 00:45:18 craters and things. So, for a long time
00:45:18 --> 00:45:20 people just assumed that there was going to be life
00:45:20 --> 00:45:23 on the other world. Then we started to learn that Mars
00:45:23 --> 00:45:26 actually really cold, it's got a thin atmosphere, and Venus,
00:45:26 --> 00:45:29 it's got a runaway greenhouse effect. So it's very, very hot and the air
00:45:29 --> 00:45:32 pressure would be very, very intense, you know, about 90 atmospheres or something
00:45:32 --> 00:45:35 and temperatures of over 400 degrees Celsius,
00:45:35 --> 00:45:38 450 something degrees Celsius, and possible sulfuric acid
00:45:38 --> 00:45:39 rain from the clouds.
00:45:40 --> 00:45:42 Stuart Gary: We've got snow on the cloud tops by the way.
00:45:42 --> 00:45:45 Jonathan Nally: We've got a far more sophisticated idea of what
00:45:45 --> 00:45:48 things are like out there now. But yeah, back in the, back in the early days when we didn't
00:45:48 --> 00:45:51 really know, people just assumed so. But you know, goodness
00:45:51 --> 00:45:54 knows how many things we take for granted as being true right
00:45:54 --> 00:45:57 now, this year, in 2025, which 100 years from
00:45:57 --> 00:46:00 now or 50 years, will be considered complete
00:46:00 --> 00:46:00 nonsense.
00:46:00 --> 00:46:03 So, I'm not critical of, people who thought various things in
00:46:03 --> 00:46:06 past times when they were, had some reason to think
00:46:06 --> 00:46:09 that might have been. It's when you get people who just totally
00:46:09 --> 00:46:12 ignore the evidence or you know, try and work their way around the
00:46:12 --> 00:46:15 evidence. So for instance, Lowell look at finding
00:46:15 --> 00:46:18 canals on Mars, but no one else could see them. But he just sort of stuck with
00:46:18 --> 00:46:20 it because he was, he was sure that there were canals on Mars and no one else could
00:46:20 --> 00:46:23 see them. So that's when you, have problems with.
00:46:23 --> 00:46:26 Stuart Gary: Well, the problem was he didn't translate Schiaparelli's original
00:46:26 --> 00:46:29 comments correctly. Schiaparelli was talking about canali, but
00:46:29 --> 00:46:31 he didn't mean canals, he meant channels, something.
00:46:31 --> 00:46:34 Jonathan Nally: Like water channels or riverbeds, that kind of thing. Yeah, they got translated
00:46:34 --> 00:46:36 into canals, which in English means an
00:46:36 --> 00:46:38 artificial water channel.
00:46:38 --> 00:46:41 Stuart Gary: Well, they were building a huge canal network in England at the time,
00:46:41 --> 00:46:41 weren't they?
00:46:41 --> 00:46:44 Jonathan Nally: Yeah. Yeah. And, And he was, he was essentially seeing what
00:46:44 --> 00:46:47 he wanted to see. He got it into his mind and that was the end of it.
00:46:47 --> 00:46:50 And, Yeah, well, that mean that's just a human failure,
00:46:50 --> 00:46:53 isn't it, really? And on that philosophical note, Stuart Gary, we just solved all
00:46:53 --> 00:46:56 the world's problems once again, aren't we Good. And I'll see you next
00:46:56 --> 00:46:56 month.
00:46:56 --> 00:46:59 Stuart Gary: That's science editor Jonathan Nelly. And this is Space
00:46:59 --> 00:46:59 Time.
00:47:15 --> 00:47:17 And that's the show for now. Space Time
00:47:17 --> 00:47:20 is available every Monday, Wednesday and Friday through
00:47:20 --> 00:47:23 Apple Podcasts, itunes, Stitcher, Google
00:47:23 --> 00:47:26 Podcast, Pocketcasts, Spotify,
00:47:26 --> 00:47:28 acast, Amazon Music,
00:47:28 --> 00:47:31 bitesz.com, soundcloud, YouTube Music,
00:47:31 --> 00:47:34 your favorite podcast download provider, and from
00:47:34 --> 00:47:36 spacetimewithstuartgary.com
00:47:36 --> 00:47:39 spacetime's also broadcast through the National Science
00:47:39 --> 00:47:42 foundation on Science Zone Radio and on both
00:47:42 --> 00:47:45 iHeartradio and TuneIn radio. And
00:47:45 --> 00:47:48 you can help to support our show by visiting the SpaceTime
00:47:48 --> 00:47:51 Store for a range of promotional merchandising goodies,
00:47:51 --> 00:47:54 or by becoming a SpaceTime patron, which gives you
00:47:54 --> 00:47:57 access to triple episode commercial free versions of the show,
00:47:57 --> 00:48:00 as well as lots of bonus audio content which doesn't go to
00:48:00 --> 00:48:03 air, access to our exclusive Facebook group, and
00:48:03 --> 00:48:05 other rewards. Just go to spacetime with
00:48:05 --> 00:48:08 stuartgary.com for full details.
00:48:09 --> 00:48:12 Voice Over Guy: You've been listening to Space Time with Stuart Gary This
00:48:12 --> 00:48:14 has been another quality podcast production from
00:48:14 --> 00:48:15 bitesz.com