S27E57: Rewriting Cosmic History: The Surprising Growth of Early Galaxies

[00:00:00] This is SpaceTime Series 27 Episode 57 for broadcast on the 10th of May 2024.

[00:00:06] Coming up on SpaceTime, new observations show galaxies evolved much faster than previously thought,

[00:00:12] how the moon turned itself inside out and a new crew takes over aboard China's space station.

[00:00:19] All that and more coming up on SpaceTime.

[00:00:24] Welcome to SpaceTime with Stuart Gary

[00:00:28] A new study suggested star bars found in the centres of many spiral galaxies,

[00:00:48] including our own Milky Way, indicate that early galaxies evolved much faster than previously thought.

[00:00:53] The findings reported in the journal The Monthly Notices of the Royal Astronomical Society

[00:00:58] looked back more than 10 billion years in time, showing how the universe's early

[00:01:03] galaxies were less chaotic and developed more quickly. Astronomers used a web-space

[00:01:08] telescope to search for evidence of bar formation when the universe was just a few billion years old.

[00:01:14] As these elongated strips of stars develop, they regulate star formation within a galaxy,

[00:01:19] pushing gas into the galaxy's central region. And their presence tells scientists that galaxies

[00:01:25] have entered a settled, mature phase. Now previous studies carried out using

[00:01:30] NASA's Hubble Space Telescope had been able to detect star bars forming in galaxies up to

[00:01:35] around 8 or 9 billion years ago. But the increased sensitivity in wavelength range offered by web

[00:01:41] means astronomers were able to see the phenomenon happening even further back in time. The new findings

[00:01:47] mean scientists will have to rethink their theories about galaxy evolution during the

[00:01:51] early stages of the universe's formation. The studies lead author Zoe Laconte from Durham

[00:01:56] University, says galaxies in the early universe are maturing much faster than previously thought,

[00:02:01] which is a surprise because one would have expected the universe at that stage to be a very

[00:02:06] turbulent place with lots of collisions between galaxies and a lot of gas that hadn't yet

[00:02:10] transformed into stars. However, web seeing a lot of these star bars much earlier in the life of

[00:02:16] the universe, and that means galaxies were far more settled at that stage in their revolution

[00:02:21] than previously thought. The Compton colleagues used web to look for bar formation in galaxies

[00:02:26] as they would have been seen between 8 and 11 and a half billion years ago.

[00:02:31] Universe itself is 13.8 billion years old. Now of the 368 spiral galaxies observed,

[00:02:38] the authors found that almost 20% of them had star bars. That's twice as many as what was

[00:02:43] observed by Hubble. And this implies that star bar driven galaxy evolution has been

[00:02:48] happening much longer than previously thought. The findings also mean current simulations

[00:02:53] of the universe will need to be scrutinized to see if astronomers can still get the same results

[00:02:58] as the observations made by web. Still, as astronomers look further back in time and space,

[00:03:03] they were able to see fewer and fewer star bar forming galaxies. They say this might be because

[00:03:09] galaxies at an even earlier stage of the universe's evolution might not have been as well formed.

[00:03:14] There's also no way currently of seeing shorter bars of stars which are less easy to spot,

[00:03:19] even with the increased telescopic power offered by web. The authors now want to investigate even

[00:03:24] more galaxies in the early universe to see if they've also formed star bars. Eventually,

[00:03:29] they hope to look back some 12.2 billion years to see star bar growth over time and maybe even

[00:03:35] determine the mechanisms behind it. See, understanding this will also help us better

[00:03:41] understand the evolution of our own galaxy which is also a bad spiral. This is spacetime.

[00:03:48] Still to come, how the moon turned itself inside out and a new crew takes over aboard China's

[00:03:54] space station. All that and more still to come on spacetime. A new study combining computer

[00:04:15] simulations and spacecraft observations helping to explain the long-standing mystery surrounding

[00:04:20] the moon's lopsided geology. About four and a half billion years ago, small Mars-sized

[00:04:26] planet called Thea smashed into the early proto-earth, turning both bodies into a vast magma ocean,

[00:04:32] which coalesced eventually solidifying into the Earth we know today. Now, the force of that cataclysmic

[00:04:39] impact event also flung lots of molten ejector and debris out into space. Slowly this debris

[00:04:46] created and coalesced, cooling and solidifying to form the moon. This scenario of how the

[00:04:51] Earth's moon came to be, known as the giant impact theory, is largely agreed upon by most astronomers.

[00:04:58] But the minute details of exactly how it happened are still a matter of intense debate.

[00:05:03] Now a new study reported in the journal Nature Geoscience offers important fresh insights into

[00:05:08] the evolution of the lunar interior and consequently the moon as a whole. Most of what's

[00:05:14] known about the origins of our moon comes from analysis of rock samples collected by the

[00:05:18] Apollo astronauts more than 50 years ago, and they then combine that with theoretical models.

[00:05:24] The samples of the exotic lava rocks brought back from the moon show surprisingly high

[00:05:28] concentrations of titanium. And later, satellite observations found that these titanium-rich

[00:05:34] volcanic rocks are primarily located on the moon's nearside. But how and why they got

[00:05:40] there has remained a mystery until now. Now because the moon formed fast and hot,

[00:05:45] it was likely also covered by a global magma ocean. And as the molten rock gradually cooled and

[00:05:51] solidified, it formed the moon's mantle and bright crust, which we see when we look up at

[00:05:55] the full moon at night. But deep below the surface, the young moon was still widely out of

[00:06:00] equilibrium. Models suggested that the last drags of the magma ocean would have crystallized

[00:06:05] into dense minerals including ilmenite, a mineral containing titanium and iron.

[00:06:10] The new studies lead author Wai Ganglian from the University of Arizona says that because

[00:06:15] these heavy materials are dented in the mantle underneath, it creates a gravitational instability

[00:06:20] and consequently you'd expect this layer to sink deeper into the moon's interior.

[00:06:24] Somehow in the millennia that followed, this dense material did sink into the interior,

[00:06:29] mixed with the mantle, melted and then returned to the surface as titanium-rich lava flows,

[00:06:34] which are detected on the lunar surface today. That means the moon somehow literally turned

[00:06:40] itself inside out. But there's been very little physical evidence to shed light on the exact

[00:06:45] sequence of events during this critical phase of lunar history. And there's a lot of disagreement

[00:06:50] in the details of what actually went down, quite literally. For example, did the materials sink as

[00:06:56] it formed a little at a time? Or did it sink all at once after the moon fully solidified?

[00:07:02] Did it sink into the interior globally and then rise up again on the lunar nearside?

[00:07:07] Or did it migrate to the nearside from the far side and then sink?

[00:07:11] Each of these models holds profound implications for the geologic evolution of the moon.

[00:07:16] Our previous research predicted that the dense layer of titanium-rich material beneath the crust

[00:07:21] first migrated to the nearside of the moon, possibly triggered by a giant impact on the

[00:07:25] far side, and then sunk into the interior in a network of sheet-like slabs, cascading

[00:07:30] into the lunar interior almost like waterfalls. But when that material sank, it left behind

[00:07:36] a small remnant in a geometric pattern of intersecting linear bodies of dense titanium-rich

[00:07:41] material beneath the crust. And Liang and colleagues have seen a similar pattern when they examine

[00:07:46] subtle variations in the moon's gravitational field, revealing a network of dense material

[00:07:51] lurking below the crust. So the authors compared simulations of a sinking limonite-rich layer

[00:07:57] to a set of linear gravitational anomalies detected by NASA's GRAIL mission,

[00:08:01] to spacecraft orbit the moon in 2011 and 2012, measuring tiny variations in its gravitational

[00:08:07] pull. These linear anomalies surround a vast dark region of the lunar nearside covered by

[00:08:13] volcanic flows known as Marais Latin for sea. The authors found that the gravity signatures

[00:08:19] measured by the GRAIL mission are consistent with ilmenite-layer simulations, and that the

[00:08:24] gravity field can be used to map out the distribution of the ilmenite remnants left

[00:08:29] after the sinking of the majority of the dense layer. Liang says the analysis shows that the models

[00:08:34] and data are telling a consistent story. Ilmenite materials migrated to the nearside and then

[00:08:40] sank into the interior in sheet-like cascades, leaving behind a vestige that causes anomalies

[00:08:46] in the moon's gravity field today as seen by GRAIL. Now importantly, the linear gravity

[00:08:51] anomalies are interrupted by the largest and oldest impact basins on the nearside of the

[00:08:55] moon and therefore must have formed earlier than those impacts. Now based on these cross-cutting

[00:09:01] relationships, the authors suggested the ilmenite-rich layer sank prior to 4.22 billion years ago,

[00:09:07] which is consistent with it contributing to later volcanism seen on the lunar surface.

[00:09:12] While the detection of lunar gravity anomalies provides evidence for the sinking of a dense

[00:09:16] layer in the moon's interior and allows for a more precise estimate of how and when the event

[00:09:21] occurred, what is seen on the lunar surface adds even more intrigue to the story.

[00:09:25] That's because of the lunar dichotomy, the incredible difference between the moon's near and far sides.

[00:09:32] See, the moon is fundamentally lopsided with an nearside facing the earth and especially the

[00:09:37] dark region known as Aegeanus proscylarum being lower in elevation, with a thinner crust

[00:09:43] largely covered with lava flows and high concentrations of typically rare elements

[00:09:47] like titanium and thorium. The thicker far side of the moon differs in each of these respects.

[00:09:53] Somehow the overturn of the lunar mantle is thought to be related to the unique structure

[00:09:58] and history of the nearside proscylarum region, but the details of that overturn are also a matter

[00:10:04] of considerable debate among scientists. This new work helps connect some of those dots between

[00:10:10] the geophysical evidence for the interior structure of the moon and computer models of its

[00:10:14] evolution. For the first time, scientists have physical evidence showing them what was

[00:10:19] happening in the moon's interior during a crucial stage in its evolution.

[00:10:24] This is space time. Still to come, a new crew takes charge of China's space station

[00:10:30] and we explore the constellation Scorpius, the spectacular M6 and M7 open star clusters

[00:10:37] and the Etta Akurids meteor shower produced by Halley's Comet in the May edition of Skywatch.

[00:10:43] China's Shenzhou 17-Tai can also return safely to Earth after spending six months aboard Beijing's

[00:11:03] Tian Gong space station. The crew led the Nidong Feng and the Gobi Desert region of Inner Mongolia

[00:11:10] nine hours after handing over space station operations to the new Shenzhou 18 crew who had

[00:11:15] arrived on station several days earlier. The Shenzhou 18 crew docked with the Tian He call

[00:11:20] module of the space station a day after launching aboard a Longmarch 2F rocket from

[00:11:25] the Jai Kuan satellite launch center in northwestern China. Beijing claims the Shenzhou 17 crew

[00:11:31] conducted 84 experiments in various disciplines such as life sciences, space medicine and

[00:11:36] material sciences and they undertook two space walks. The Chinese official Xinguai news agency

[00:11:43] claims the Shenzhou 18 crew will now undertake experiments in basic physics, microgravity,

[00:11:48] material science, space medicine, life sciences and technology and they'll also try to set

[00:11:54] up an aquarium aboard the space station to raise fish in zero gravity for food. This is space time

[00:12:18] and time out at NOS to the skies and check out the celestial sphere for the month of May

[00:12:23] on Skywatch. May is the fifth month of the year in both the Julian Angigorian calendars.

[00:12:29] The month was named for the Greek goddess Maya who was identified with the Roman era goddess

[00:12:34] of fertility Bernardia whose festival was held in May. But I guess more importantly for many of our

[00:12:40] listeners, May typically marks the start of summer vacation season in the United States and Canada.

[00:12:46] Let's start out tour of the night skies by looking east where you'll see the constellation

[00:12:50] Scorpius the Scorpion. In Greek mythology the constellation was named after Scorpius who

[00:12:56] was sent to earth by the goddess Gaia in order to slay Orion the Hunter after he bursted that

[00:13:01] he could kill all the animals on earth. Scorpius stung Orion in the shoulder but Orion's life was

[00:13:08] spared by Ophiuchus the Healer and it was placed in the heavens along with Scorpius who continued

[00:13:14] to pursue him for eternity. Orion the Hunter has become the hunted forever with Scorpius rising

[00:13:20] in the east this time of year to triumphantly chase and defeat Orion who sets in the west.

[00:13:25] Meanwhile Ophiuchus the Healer rises in the east following behind Scorpius to chase and

[00:13:31] crush him into the earth as the scorpion sets in the west. And so this ancient story continues to

[00:13:37] play out in the heavens year after year. Interestingly parts of the story predate the Greeks

[00:13:43] with Orion known in ancient Egypt as Osiris the god of the underworld and of regeneration.

[00:13:49] The brightest star in Scorpius is Alpha Scorpi or Antares the Scorpion's heart.

[00:13:55] In ancient Greek the name Antares means the equal arrival of Mars the god of war.

[00:14:01] That's because it scored an orange appearance is similar to that of the red planet and it passes

[00:14:05] very close to Mars every 780 years. Easily seen with the unaided eye and Tares is some 550 light

[00:14:14] years away but it looks so bright because it's around 57,500 times as luminous as the sun and

[00:14:20] he's one of the largest known stars in the universe. And Tares is a red supergiant about 18

[00:14:27] times the mass and 883 times the diameter of the sun. Were it placed where the sun is in our solar

[00:14:34] system it would engulf all the terrestrial planets Mercury Venus Earth and Mars and its visible surface

[00:14:40] would extend almost as far out as Jupiter. A light year is about 10 trillion kilometers

[00:14:46] the distance a photon can travel in a year at 300,000 kilometers per second the speed of

[00:14:51] light in a vacuum and the ultimate speed limit of the universe. Astronomers believe Antares began

[00:14:57] life around 12 million years ago as a spectrotype O or B blue star. Astronomers describe stars in

[00:15:04] terms of special types a classification system based on temperature and characteristics. The

[00:15:10] hottest most massive and most luminous stars are known as spectrotype O blue stars.

[00:15:15] They're followed by spectrotype B blue white stars then spectrotype A white stars,

[00:15:21] spectrotype F whitish yellow stars, spectrotype G yellow stars that's where our sun fits in.

[00:15:27] Then there's spectrotype K orange stars and the coolest and least massive stars are known as

[00:15:32] spectrotype M red stars. Each special classification system can also be subdivided using a numeric

[00:15:39] digit to represent temperature with zero being the hottest and nine the coolest.

[00:15:44] And then you add a Roman numeral to represent luminosity. So put it all together and you can

[00:15:49] describe our sun as being a G2V or G2V yellow dwarf star one of millions spread across our galaxy.

[00:15:58] Also included in the stellar classification system are special types LT and Y which are

[00:16:04] assigned to failed stars known as brown dwarves some of which were actually born as spectrotype

[00:16:09] M red stars but became brown dwarves after losing some of their mass. Brown dwarves fit into a unique

[00:16:15] category between the largest planets which are about 13 times the mass of Jupiter and the smallest

[00:16:20] spectrotype M red dwarf stars which are about 75 to 80 times the mass of Jupiter or 0.08 solar

[00:16:27] masses. Like the similar sized red giant betelgeuse in the constellation Orion and Tari's almost

[00:16:34] certainly end its life as a spectacular type 2 or core collapse supernova probably sometime within

[00:16:40] the next 100,000 years or so. When it does explode it'll appear as bright as the full moon for several

[00:16:46] months on end and will be clearly visible during daylight hours here on earth. And Tari's has

[00:16:52] a companion star Antares B located between 224 and 529 astronomical units away from the primary

[00:17:01] astronomical unit is the average distance between the earth and the sun which is about 150

[00:17:06] million kilometers or 8.3 light minutes. Spectral analysis of Antares B indicates it's

[00:17:12] pulling a lot of material off its bloated red super giant companion. Located near Antares

[00:17:19] is the M4 globular cluster. Globular clusters are tight balls densely packed with thousands

[00:17:25] to millions of stars which were either all originally formed at the same time from

[00:17:30] the collapse of the same molecular gas and dust cloud or alternatively their galactic centers.

[00:17:35] There remains a vanishing galaxies that have been merged into the Milky Way galaxy over billions

[00:17:40] of years. M4 is composed of a million or so stars originally born some 12 billion years ago.

[00:17:47] The M4 globular cluster is located some 7,200 light years away making it one of the nearest

[00:17:53] globular clusters to earth. Easily seen through a pair of small binoculars it covers an area

[00:17:59] of the sky as seen from earth as big as the full moon. Astronomers estimate there are some

[00:18:04] 150 or so globular clusters orbiting in the halo of the Milky Way. Located near the tail of the

[00:18:11] scorpion are two open star clusters known as M6 and M7. Open star clusters are loosely bound

[00:18:18] groups of a few thousand stars which all originally formed from the same molecular

[00:18:23] gas and dust cloud at the same time but are not as densely bound as globular clusters.

[00:18:28] Open clusters generally survive for a few hundred million years with the most massive

[00:18:32] one surviving for maybe a few billion years. Now in contrast the far more massive globular

[00:18:37] clusters exert far stronger gravitational attraction on their members which is why

[00:18:42] they can survive so much longer. M6 which is also known as the butterfly cluster is some

[00:18:47] 12 light years across and located about 1600 light years away. It contains around 80 stars

[00:18:54] which are all less than 100 million years old which is quite young in cosmic terms.

[00:18:59] The M7 or Ptolemy cluster is named after the famous Greek astronomer and mathematician

[00:19:04] Claudius Ptolemy. It's about 980 light years away and is far more dispersed than M6 covering

[00:19:10] an area around 25 light years across and at around 200 million years it's about twice as old.

[00:19:18] By the way the M in terms like M4, M6 and M7 are abbreviations for Messier in honour of

[00:19:25] the 18th century French astronomer Charles Messier who developed an astronomical catalogue

[00:19:30] of fuzzy nebulous objects in the skies. See Messier was a comet hunter and he compiled

[00:19:36] a list of 103 fuzzy objects which weren't comets and served from his perspective could be

[00:19:42] ignored. Later other astronomers added additional celestial objects to the list bringing the present

[00:19:47] catalogue up to 110. Our solar system in fact most of the stars we see when we look up in the night

[00:19:54] sky are located in the Milky Way Galaxy's Orion arm. The Orion arm also known as the Orion spur

[00:20:01] or the Orion Cygnus arm depending on which name you prefer is some 3500 light years wide

[00:20:07] and around 10,000 light years long. The Orion arm is named after the Orion constellation

[00:20:14] which is one of the most prominent constellations in the southern hemisphere summer and northern

[00:20:18] hemisphere winter. Some of the brightest and most famous celestial objects in the constellation

[00:20:24] include Betelgeuse, Rigel, the stars of the Orion belt and the Orion Nebula all located

[00:20:30] within the Orion arm. The Orion arm is located between the Crenus agiterius arm which is

[00:20:35] more towards the galactic center from our position and the Perseus arm which is more towards the

[00:20:40] outer edge of the galaxy from our point of view. The Perseus arm is one of the two major arms of

[00:20:45] the Milky Way the other being the Skutum Centaurus arm. Long thought of as a minor structure spur

[00:20:52] if you will between the two longer adjacent arms Perseus and Crenus agiterius evidence was

[00:20:58] presented in mid 2013 that the Orion arm might actually be a branch of the Perseus arm or

[00:21:03] possibly a completely independent arm segment itself. Within the Orion arm our solar system the sun,

[00:21:10] the earth and all the other planets we know are located close to the inner rim in what's known

[00:21:15] as the local bubble about halfway along the Orion arm's length approximately 26,000 light years

[00:21:21] from the galactic center. The local bubble is a cavity in the interstellar medium in the

[00:21:26] Orion arm containing among other things the local interstellar cloud which contains our solar

[00:21:31] system and the G-cloud. It's at least 300 light years across and it has a neutral hydrogen density

[00:21:38] of just 0.05 atoms per cubic centimeter that's just one tenth of the average for the interstellar

[00:21:44] medium across the Milky Way and about a sixth out of the local interstellar cloud. The hot

[00:21:49] diffuse gas in the local bubble emits X-rays and is the result of a supernova that exploded

[00:21:55] sometime during the past 10 to 20 million years. It was once thought that the most likely

[00:22:00] candidate for the remains of this supernova was Jminga, a pulsar in the constellation Gemini.

[00:22:06] However later it was suggested that multiple supernovae in a subgroup B1 of the Pleiades

[00:22:11] moving group was more likely responsible becoming a remnant super shell. Our solar system has

[00:22:17] been travelling through this region of space occupied by the local bubble for the last 5 to

[00:22:22] 10 million years. Its current location is in what's known as the local interstellar cloud

[00:22:28] a minor region of slightly denser material within the bubble. The cloud formed when the local bubble

[00:22:34] and another bubble called the Loop 1 bubble met. Gas within the local interstellar cloud has a

[00:22:40] density of about 0.3 atoms per cubic centimeter. From what we can tell the local bubble isn't

[00:22:45] spherical but seems to be narrower in the galactic plane becoming somewhat egg shaped or elliptical

[00:22:51] and may even become wider above and below the galactic plane becoming shaped more like an

[00:22:56] hourglass. And it's not alone, it's abouting other bubbles of lesser dense interstellar medium

[00:23:02] including the Loop 1 bubble. The Loop 1 bubble was created by supernovae and stellar winds in the

[00:23:08] Scorpius Centaurus Association some 500 light years from the sun. The Loop 1 bubble also contains

[00:23:14] the starantaries that we spoke about earlier. Astronomers have identified several well I guess

[00:23:20] you'd call them tunnels which connect the cavities of the local bubble with that of the Loop

[00:23:24] 1 bubble. Collectively they've been referred to as the loopers tunnel. Other bubbles which are adjacent

[00:23:30] to our local bubble and then is the Loop 2 bubble and the Loop 3 bubble. Looks like astronomers

[00:23:35] still have a problem when it comes to thinking up cool names. Also visible this month is the

[00:23:41] Etta Aquarids Meteor Shower which is generated as the earth passes through the dust and debris

[00:23:46] trail left behind by Halley's Comet. Comet P1 Halley's a well known short period comet

[00:23:52] which visits the inner solar system every 75 to 76 years. The 15 kilometer wide mountain of rock and

[00:23:59] ice will make its next close-up appearance in 2061. It's named in honor of the British astronomer

[00:24:05] Edmund Halley who in 1705 after examining ancient Chinese Babylonian and medieval European records

[00:24:12] successfully predicted its return in 1758. However he died in 1742 before his prediction

[00:24:19] could be confirmed. The comet's highly elliptical and elongated orbit takes it from between the orbits

[00:24:25] of Mercury and Venus out almost as far as the orbit of Pluto. Halley's orbit is in retrograde

[00:24:31] meaning it orbits the Sun in the opposite direction to the planets that is clockwise

[00:24:36] from above the Sun's northern pole. This retrograde orbit results in it having one of the highest

[00:24:41] velocities relative to the Earth of any object in the solar system traveling at some 70.56

[00:24:47] kilometers per second or if you prefer 254,016 kilometers per hour. As well as the etoagrid's

[00:24:55] meteor shower every May Halley's comet also produces the Orionids meteor shower in late October.

[00:25:01] Astronomers think Comet Halley was originally a long period comet which took thousands of years

[00:25:06] to travel to the inner solar system from the Oort cloud but was gravitationally perturbed

[00:25:11] into its current orbit by close encounters with the giant outer planets. The Oort cloud is

[00:25:16] a hypothetical sphere of comets and asteroids beyond the heliosphere, a mixture of vagabonds from

[00:25:23] the solar system and objects from deep space which have been collected by the Sun's gravitational

[00:25:28] pull. Occasionally as the Sun passes by another star an Oort cloud object will get

[00:25:33] perturbed and be flung towards the inner solar system. The etoagrid's meteor shower runs

[00:25:38] from the 19th of April through to the 28th of May, peaking around May the 5th with around

[00:25:44] 55 meteors an hour making it one of the southern hemisphere's best celestial showers.

[00:25:50] However back in 1975 they were running 95 meteors an hour and in 1980 it was up to 110.

[00:25:58] Even better the bright yellow meteors often appear as streaks known as trains.

[00:26:03] As their name suggests they radiate out from the direction of the constellation Aquarius

[00:26:08] and the star Etto Aquari. Just look towards the east after midnight and before dawn for

[00:26:13] the best view. And now with the rest of May sky watch we're joined by Jonathan Nally from Sky and

[00:26:19] Telescope Magazine.

[00:26:20] G'day Stuart, well where I live at least daylight savings is over now we're heading towards

[00:26:24] winter so the night's getting longer which is good for stargazing. There's actually a really

[00:26:28] good time for stargazing this time of the year if you live in the southern hemisphere.

[00:26:31] I can't speak for our friends in the north but for us down here it's really good because

[00:26:35] there are lots of great southern only constellations visible the ones that we can only see

[00:26:40] down here. So we've got the Southern Cross for a start it's just standing upright and really high

[00:26:44] up in the south in the middle part of the evening you just can't miss it. At other times in the

[00:26:49] year it's down lower on the horizon and it might get blocked out by trees or houses or something

[00:26:53] but at the moment it's really high up in the sky. To its left are two bright stars the two

[00:26:58] brightest stars of the constellation Centaurus. Astronomers call them the two pointers because

[00:27:02] if you draw a line through them you keep the line going it more or less points towards the

[00:27:06] Southern Cross if you're having trouble finding the Southern Cross. Now if you have good dark skies

[00:27:10] and you can see the Milky Way which unfortunately most people in cities can't see if you can spot

[00:27:15] the large dark area near the Southern Cross this is a huge cloud of interstellar gas and dust

[00:27:21] called the coal sacked. I wouldn't anchor it at the coal sacked because it looks that it's just

[00:27:26] this big dark looking patch in the Milky Way and that's because it's big interstellar

[00:27:30] cloud as I said and it's just blocking out the light of the stars at the behind it so it's

[00:27:34] in front of the background star so that makes any sense to the right of the Southern Cross as we look

[00:27:40] down to the south you've got these fantastic constellations called Corina, Vela and Puppas

[00:27:45] which most people have never heard of but they're really good and they're full of fantastic things

[00:27:49] you see even just for the pair of binoculars. You get a pair of binoculars and just sweep

[00:27:53] through this area with them and you can see all these star clusters and you can make out

[00:27:56] a few nebuline just if you use what's called averted vision don't look directly at it look

[00:28:00] out of the side of your eye and that means that the light is falling on the arid or retina

[00:28:04] that's better for night viewing than the middle part of your retina which is better for day view

[00:28:09] and if you've got a small telescope even if you can hold one or friends got one or next door

[00:28:13] neighbor it's even better you get a fantastic view of the Milky Way through there. Now if you

[00:28:18] get hold of a star chart or maybe an astronomy app on your phone see if you can find two things

[00:28:23] particularly one's called Omega Centauri which is an enormous what they call globular star

[00:28:29] and there's another one it's a galaxy called NGC 5128 very imaginative some people call it Centaurus

[00:28:36] A and Centaurus A and NGC 5128 are basically the same object but I was taken to task once by an

[00:28:42] astronomer because NGC 5128 is the catalog number of the galaxy. Centaurus A is the name

[00:28:50] given to the source of radio waves coming out of this galaxy because it's emitting lots of radio

[00:28:55] waves when they're first being first maps of the night sky radio wavelengths this is one of the

[00:28:59] things that re-sput out the Cineclaw Centaurus A and then they matched it with this galaxy so if you

[00:29:04] have dark sky untouched by light pollution you should be able to spot these two things even with

[00:29:08] the naked eye just little fuzzy blobs they're not point like like the star they're like little

[00:29:13] fuzzy blobs but then if you get a double strap on them you can see what they really are okay

[00:29:17] because the eye is not good enough to make out any of the detail in it. What else we've got

[00:29:21] over in the west just after the sun has shed you can see the constellation Orion the hunter

[00:29:25] also shedding nearby we've got Sirius the brightest star in the night sky and the brightest star in

[00:29:30] a constellation Tainist Major or the greater dog a little bit to the north of Sirius we've got another

[00:29:36] star called Prasion which is the brightest star in Tainist Minor but lesser dog there are two

[00:29:42] dog constellations up there sort of right next to each other down in the southwest we've got

[00:29:46] another bright star called Canopus the second brightest star in the night sky you can really

[00:29:50] only see that one this time of year at least from Southern Hemisphere now a lot of people

[00:29:55] don't realize with many of the stars we just can talk about brighter stars right so

[00:29:59] many people don't realize that many of the stars in the night sky are not single stars

[00:30:03] they are actually multiple star systems with like two three four

[00:30:07] like you know some of them some of them got six stars all very closely bound to one another

[00:30:12] yeah sounds a bit of an outlier like that in being a solo star most systems in the Milky Way

[00:30:17] and elsewhere I guess in the universe are multiple systems multiple systems exactly right so our

[00:30:22] song's on its own but so many stars out there are multiples and but when you look up in the

[00:30:27] night sky just with your own eyes you can't see that you can't detect that some of these stars

[00:30:32] are multiple stars so for instance I mentioned Alpha Centauri just one of the stars of the

[00:30:37] two pointers when you look through a telescope at Alpha Centauri even a small backyard

[00:30:41] telescope you can see that it's two stars just look with your own eyes it's one star

[00:30:45] but look through a telescope and it's two stars so that's very very common there's even a third

[00:30:50] star in that system called Proxima Centauri but it's much harder to spot as it's very very faint

[00:30:55] in that fair distance way from the other two most people sort of really wouldn't have a chance

[00:30:59] of seeing that you've really got to know where you're looking and what you're looking for

[00:31:03] but Alpha Centauri is a classic example of of the brighter star in constellation but it's

[00:31:08] actually two stars and that's very very common up there looking at the eastern sky the other

[00:31:12] half of the sky during mid-even we've got the constellation Scorpius just beginning to poke its

[00:31:17] nose up over the horizon well it's couldn't say it's nose it's stinger and it's and it's claws

[00:31:23] it's poking nose up over the horizon and as the night progresses in the earth turns a bit more

[00:31:28] we'll see the full constellation coming out and becoming visible for us in the south here that's

[00:31:33] a good sign that winter's just around the corner for our friends in the north it's a good sign

[00:31:37] that summer is just around the corner and as the earth turns even a bit more as the night

[00:31:42] progresses after Scorpius has come up it's going to be followed by this constellation Sagittarius

[00:31:48] now like most constellations the star pattern of Sagittarius really looks nothing like what it's

[00:31:54] supposed to represent which is an archer right most constellations up there just don't look

[00:31:59] anything like what their mythology or their name suggests i mean there's a constellation called

[00:32:05] triangle which is a triangle which is just three stars joined together that's really

[00:32:10] that's really quite easy but Scorpius Scorpius actually does have the shape of a scorpion it really

[00:32:16] is quite amazing when you do the join the dots thing between the stars it really does look like a

[00:32:21] scorpion and stands out so well it really is quite spectacular other spectacular constellations

[00:32:27] like say Orion don't really see a person there but if you join the dots and add a bit more you

[00:32:31] can get a person the southern cross is quite obviously a cross there are a few other ones

[00:32:35] that are that are similar to their nameshakes but i think Scorpius is probably the best of them all

[00:32:40] now let's look at the planets Jupiter which has been nice and bright above the western horizon up at

[00:32:45] sunset unfortunately now is too close to the sun you've seen it'll be back in our skies in our

[00:32:51] morning skies in late June and like Jupiter Venus too is too close to the sun that he's

[00:32:57] seen at the moment so again i'm going to have to use that one on this for this month

[00:33:01] the other three planets are all to be seen rising above the eastern horizon in the early hours of

[00:33:06] the morning so you've got to be getting up early or staying up very late will be some sort of

[00:33:11] night hour in order to see these because Saturn is rising just after 2 a.m at the start of May

[00:33:17] Mars follows up over the horizon about a little over an hour later and then Mercury a little

[00:33:23] over an hour after Mars so one after the other about an hour apart now the good thing this

[00:33:29] month is that you have trouble identifying which are the planets for these three planets in particular

[00:33:35] it's going to be easy this month because you're going to be able to use the moon

[00:33:39] to help you identify them that's because as the moon goes along in its orbit it sort of passes

[00:33:44] from our perspective from our point of view our our line of sight yeah the moon sort of

[00:33:49] passes by each of the planets in a row um it goes around the night sky and yeah it's four

[00:33:55] week cycle and let's do it is the next time of May that's Jonathan Nally from Sky and Telescope

[00:34:01] magazine and this space time and that's the show for now space time is available every Monday

[00:34:23] Wednesday and Friday through Apple podcasts iTunes Stitcher Google podcast pocket casts

[00:34:29] Spotify a cast amazon music bites dot com soundcloud youtube your favorite podcast download

[00:34:36] provider and from spacetime with stewart gary dot com spacetimes also broadcast through the

[00:34:42] national science foundation on science zone radio and on both i heart radio and tune in radio

[00:34:49] and you can help to support our show by visiting the spacetime store for a range of

[00:34:53] promotional merchandising goodies or by becoming a spacetime patron which gives you access to

[00:34:58] triple episode commercial free versions of the show as well as lots of bonus audio content

[00:35:03] which doesn't go to air access to our exclusive facebook group and other rewards just go to

[00:35:09] spacetime with stewart gary dot com for full details and if you want more spacetime please check out

[00:35:15] our blog where you'll find all the stuff we couldn't fit in the show as well as heaps of

[00:35:19] images news stories loads of videos and things on the whereby find interesting or amusing

[00:35:24] just go to spacetime with stewart gary dot tumblr.com that's all one word and that's

[00:35:30] tumblr without the e you can also follow us through at stewart gary on twitter at spacetime

[00:35:36] with stewart gary on instagram through our spacetime youtube channel and on facebook

[00:35:41] just go to facebook dot com forward slash spacetime with stewart gary you've been

[00:35:46] listening to spacetime with stewart gary this has been another quality podcast production from

[00:35:52] bites dot com