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March 2018: Black Holes and Revelations

March 2018

Sparkly, but in a good way! In the show this time, we talk to Prof. Michael Shara about novae and the American Museum of Natural History, Shruti Badole rounds up the latest news, and we find out what we can see in the March night sky from Ian Morison, Jasmine Chan-Hyams and Gaby Perez.

The News

This month in the news: the most distant supernova ever discovered, the discovery of some of the most massive black holes in the universe and water content in the TRAPPIST-1 planets.

Astronomers have discovered the most distant supernova ever detected. A supernova is an explosion of a massive star that takes place at the end of its life cycle. The explosion in news took place around 10.5 billion years ago, when the universe was only about a quarter of its present age. The supernova, named DES16C2nm, was discovered by an international team of astronomers as part of the Dark Energy Survey that maps millions of galaxies to study dark energy, a mysterious quantity that is believed to cause an accelerated expansion of the universe.

DES16C2nm belongs to a rare class of supernovae known as superluminous supernovae (also known as SLSN). Compared to normal supernovae, SLSNs are brighter at their peaks by factors of tens to hundreds and were discovered only 10 years ago. The study of the most distant supernova was published in February 2018 in the Astrophysical Journal. The supernova was first detected in August 2016, and its distance and brightness confirmed using the Very Large Telescope (VLT) and Magellan Telescope in Chile, and the Keck Observatory in Hawaii. In a statement, the lead author of the paper, Dr Mathew Smith from the University of Southampton, said: "It's thrilling to be part of the survey that has discovered the oldest known supernova. DES16C2nm is extremely distant, extremely bright, and extremely rare - not the sort of thing you stumble across every day as an astronomer. As well as being a very exciting discovery in its own right, the extreme distance of DES16C2nm gives us a unique insight into the nature of SLSN. The ultraviolet light from SLSN informs us of the amount of metal produced in the explosion and the temperature of the explosion itself, both of which are key to understanding what causes and drives these cosmic explosions."

Currently, astronomers use a class of supernovae known as Type Ia supernovae as standard candles. Standard candles are astrophysical objects with known and fixed luminosity and are used to determine astronomical distances. The exact intrinsic brightness of Type Ia supernovae is known; the apparent brightness is a function of the distance, thus making them useful as standard candles. Since SLSNs can be a hundred times brighter than Type Ia supernovae, they could potentially be used as standard candles. But not many SLSNs are known and the key to use them as standard candles lies in finding as many of them as possible so as to 'standardise' them by finding patterns between the light they emit and the brightness of each SLSN. The team of astronomers is hoping to find more such supernovae events at even greater distances using the Dark Energy Survey.

In other news: Astronomers from the University of Montreal and the Institute of Space Sciences (ISS) in Spain have discovered what could be the most massive black holes ever found in the universe. The black holes were detected 3.5 billion light years away using NASA's Chandra X-ray telescope. The scientists studied 72 galaxies in the middle of some of the most massive and brightest galaxy clusters in the universe and determined the mass of the black holes by analysis of the radio waves and X ray emission captured by Chandra. Around 40 percent of the black holes were found to be 10 billion times more massive than the Sun, a figure 10 times greater than the early predictions of the astronomers. The growth rate of many of these black holes was found to be faster than the stars in their host galaxies, thus contradicting earlier research that suggested that these growth rates are similar. The reason behind the ultra massiveness of these black holes remains unexplained so far.

And finally: A new study suggests that planets in the TRAPPIST-1 system could contain 250 times more water compared to the Earth. Ever since its discovery over a year ago, the TRAPPIST-1 system has generated tremendous excitement in the astronomy community because of the similarities between its planets and the Earth. In the latest study, a team of researchers at the University of Bern used computational models to simulate the planetary orbits of TRAPPIST-1 to estimate the masses of the planets, from which the individual densities and compositions of the planets were then deduced. It was found that up to 5 percent of the planets' composition could be water. To put things in perspective, consider this: only 0.02 percent of the Earth's surface is water. The study, published in the journal Astronomy & Astrophysics provides new insight into the potential habitability of the TRAPPIST-1 planets.

Interview with Prof. Michael Shara

Luke interviews Prof. Michael Shara, one of three Curators of Astrophysics at the American Museum of Natural History. The institution hosts 35 million specimens of all possible kinds, and has held exhibitions on subjects as diverse as dinosaurs, the history of Cuba and the future direction of humanity. Prof. Shara also discusses his own work on novae - binary systems producing recurrent flare-ups, and recounts his team's 20-year hunt for the location of a 580-year old nova, seen by Imperial Korean astronomers.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during March 2018.

  • Jupiter - Jupiter rises just before midnight at the beginning of the month and about one hour earlier by month's end. Initially it has a 39 arc second disk, shining at a magnitude of -2.2 but as the month progresses, its apparent diameter increases to 42.5 arc seconds and it brightens to magnitude -2.4. Jupiter will transit before dawn and so will enable the giant planet to be seen with the equatorial bands, sometimes the Great (but reducing in size) Red Spot and up to four of its Gallilean moons visible in a small telescope. Sadly, Jupiter, lying in Libra during the month, is heading towards the southern part of the ecliptic and will only have an elevation of ~20 degrees when crossing the meridian. Atmospheric dispersion will thus hinder our view and it might be worth considering purchasing the ZWO Atmospheric Dispersion Corrector to counteract its effects.

  • Saturn - Saturn, at the start of its new apparition, rises at around 3 am at the start of the month and just after 2 am at its end. With an angular size of ~16.3 arc seconds it climbs higher before dawn and so becomes easier to spot as the month progresses. Its brightness increases from +0.6 to +0.5 magnitudes during the month. The rings were at their widest a few months ago and are still, at 26 degrees to the line of sight, well open. Saturn, lying in Sagittarius, is just 3 degrees above the topmost star of the 'teapot'. Sadly, even when at opposition later in the year it will only reach an elevation of just over 15 degrees above the horizon when crossing the meridian. Atmospheric dispersion will thus greatly hinder our view and it might be worth considering purchasing the ZWO Atmospheric Dispersion Corrector to counteract its effects.

  • Mercury - Mercury gives us its best evening apparition this month when it reaches its peak height above the western horizon on March 15th when, at greatest elongation, it lies some 18 degrees west of the Sun. However, by this time its magnitude has dropped from -1.3 at the beginning of March to -0.4 magnitudes. Its magnitude continues to fall, dropping to +0.9 by 20th and soon after will be lost in the Sun's glare. Mercury flirts with Venus during the month as detailed in the highlights.

  • Mars - Mars starts the month moving quicky eastwards in Ophiuchus moving into Sagittarius on the 12th of the month as it moves towards Saturn. Now a morning object, it rises at around 2 am at the start of the month. During the month, Mars has a magnitude which increases from +0.8 to +0.3 and an angular size of just 7, increasing to 8.5, arc seconds so it will be hard to spot details on its salmon-pink surface. It will only reach an elevation of ~14 degrees before dawn at the start of the month and just 12 degrees by month's end.

  • Venus - Venus, seen low in the west after sunset shines at magnitude -3.9 all month with an angular size of ~10.3 arc seconds. Venus rises a little higher in the sky as March progresses, initially setting around one hour after the Sun but increasing to an hour and a half by month's end. It has two near conjunctions with Mercury as described in the highlights above.

  • Highlights

  • March 2nd to 4th after sunset: Venus and Mercury within 1.3 degrees of each other. After sunset on these three evenings and given a clear sky and a low western horizon, you should be able to spot Venus and Mercury. Their closest is on the 3rd when they are just 1.1 degrees apart. Binoculars might be needed to penetrate the skys residual brightness, but please do not use them until after the Sun has set. [Note: The sky brightness has been reduced in the chart.]

  • March 10th/11th before dawn: Saturn, Mars and a waning Moon. Mars below a waning Moon If clear before dawn on the 10th and 11th, looking just east of south, one should see a waning crescent Moon lying to the upper left of Mars on the 10th and Saturn on the 11th.

  • March 19th after sunset: Venus, Mercury and a very thin crescent Moon. Looking West after sunset on the 19th and given a very low western horizon, one might be able to spot Venus near Mercury which is close to maximum elongation from the Sun. A very thin crescent Moon, just two days after new, will be seen up to their left. Binoculars may well be needed, but please do not use them before the Sun has set. A tough observing challenge! [Note: the sky brightness has been reduced in the chart.]

  • March 23rd evening: The Moon in the Hyades Cluster. In the evening of the 23rd of the month, the Moon, coming towards first quarter, will lie within the Hyades cluster. After it has set from the UK it will occult Aldebaran which is a red giant star lying between our solar system and the cluster.

  • March 8th and 24th: The Alpine Valley. These are two good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image is a thin rill runs along its length which is quite a challenge to observe. The dark crater Plato will also be visible nearby. You may also see the shadow cast by the mountain Mons Piton lying not far away in Mare Imbrium. This is a very interesting region of the Moon!

  • Southern Hemisphere

    This month we welcome two new presenters, Gabriela Perez and Jasmine Chan-Hyams who tell us what we can see in the Southern Hemisphere night sky during March 2018.

  • Introduction - I'm Gaby, I work at Space Place at the Carter Observatory, in Wellington New Zealand as a telescope operator. I've been staring at the Southern Skies for most of my life. As a child I saw the fully mapped-out globe and I became fascinated with space, ever since I have wanted to explore the universe beyond. Now I bring the universe to me (mostly through collecting its light) with my eyes, a pair of binoculars or a telescope.

    And I'm Jasmine, I am a PhD Biotech student at Victoria University of Wellington. But who I am is a scientist, a star-gazer and a story-teller. We wish a fond farewell to Claire who has contributed so much to this podcast over the years. Thank you for teaching me about treasuring that moment of awe when you share a wonder of the universe with someone who has never seen anything like it before. You will be sorely missed at Space Place and we wish you all the best in your new job!

    Looking up into the night skies is one of the true delights of living in the southern hemisphere; especially here in Aotearoa, New Zealand where it is easy to get away from the bright city lights and where we a get a broader and brighter view of the Milky Way.

    Early in the month of March we can look forward to gazing upon many star studded greek heroes and mythical creatures. We can use constellations as guideposts to find deep sky objects including beautiful nebulae and special features of our southern skies.

  • The region around Orion - Our journey begins with the Greek constellation Orion, who appears in the skies after full dark in north-north west for the month of March. For many of us finding the three bright stars that form Orion's belt were probably the first thing you could proudly identify as a child. These three stars are 2nd magnitude stars. You can also see with the naked eye Betelgeuse, located in Orion's armpit; a red supergiant hundreds of times larger than our sun. Yet the brightest star of this constellation is Rigel - a blue star at Orion's ankle. Blue stars are the hottest kind of stars you'll find in the night skies while red stars are cooler and burning up the last of their heat energy. Just below his belt you'll find the Orion Emission Nebula (M42)- a huge star forming cloud - more than two widths of our moon across, it lies about 1500 light years away. With the naked eye it appears as a diffuse cloudy patch. Through a telescope you can see the clouds of dust and gas, lit up by the baby stars they are forming.

    From Orion's belt it's just a star jump to the right and up to find Sirius, the brightest star in our skies. Sirius is seriously bright at about 20 times brighter than our sun and is only 8.6 lya. Sirius is part of the Canis Major constellation - one of the two dog companions that accompany the hunter Orion. Below Canis Major you can look for the two stars that form Canis Minor. The star Procyon, in Canis Minor, forms a triangle with the 1st magnitude stars Sirius and Betelgeuse.

    Within this "southern triangle" you can look for the Monoceros unicorn constellation - home to the gorgeous Rosette nebula. This nebula has a beautiful carnation pick colouring and can be seen with binoculars in the part of the constellation closest to Betelgeuse.

    Neighboring Orion is the zodiac constellation Taurus the Bull. Taurus and his fiery eye, the red giant Aldebaran, can be found low in our Northern-Western sky after sunset where we can easily make out his V shaped horns. Near his shoulder lies the Pleiades star cluster. On a clear dark night you can see seven points of light with the naked eye but it is best viewed with a pair of binoculars. The Pleiades is a young cluster of mostly hot blue stars, the big ones that burn up all their fuel quickly -they live fast and die young. These bright blue stars are said to be seven beautiful sisters. You can find the seven sisters sheltering in the shoulder of the bull hiding from Orion's amorous intentions.

  • Crab Nebula.

    After you get an eyeful of these blue beauties you can jump down to the Crab Nebula (M1) but you'll want a telescope for this part. M1 was the fist Messier object recorded by famous French astronomer Charles Messier in 1771. To find M1 with your telescope look for Aldebaran first then follow the bull's horn to the end, it will be close to the horizon. Large apertures are needed to make out the filamentous detail. The Crab Nebula is was first viewed more than a 1000 years ago, by ancient Chinese astronomers, who recorded a bright light forming in this area. They witnessed was a supernova - a dying star. At the heart of the Crab Nebula is the pulsar, the skeleton of the dying star. Although we cannot see it with a telescope we can listen to the radio waves it emits as it spins. We can listen to the song of supernova.

    You can enjoy looking for Orion, his hunting dogs, Taurus and the unicorn Monoceros throughout the early evenings of March. Now I'll hand over to Gabriela who'll tell us what planets we can see this month and features of the skies to the south.

  • The Planets - But if you are looking for planets in March, you'll need stay up late. Venus sets shortly after the sun but becomes increasingly visible in our twilight skies towards the end of the month. Jupiter rises in the late evening about midnight in mid-March. This gas giant reflects the light of our sun and outshines Sirius, becoming the brightest object in our night sky after the Moon. For those early risers Mars and Saturn are in the eastern horizon just before dawn. Around the 7th of March the planets will line up quite nicely on either side of the waxing gibbous Moon. On the 21st of March we can observe the Autumn equinox when there night and day will be of equal length.

  • Constellations and Nebula.

    This is probably my favourite time of year to look at the Southern Skies because you can stay out late without either freezing to death or being eaten alive by mosquitoes and the most important objects stay high in the skies for longer. The Full Moon will occur mid-month on the 12th of March. So the beginning and end of March are excellent times to explore the deeper sky objects that you can only see from the southern hemisphere.

    Turning to the south horizon we look for the kite shaped Southern Cross constellation Crux. The Crux will be low in our South Eastern sky in early March after sunset. We can use the pointer stars, red-orange Alpha Centauri and blue-white Beta Centauri to identify the true Southern Cross.

    As night progresses, the Southern Cross journeys around the southern celestial pole, bringing with it the dark patches stretched out through our view of the Milky Way. Here these patched represents the Giant Moa -a now extinct large flightless bird native to New Zealand. These dark patches are where large interstellar objects, called Dark Nebulas, have blocked out the light from more distant stars - preventing their light reaching us here on Earth. Dark Nebulae are easily seen against the backdrop of the Milky Way as the large concentration of star-light surrounding them lets us see them better. The head of the Moa sits by the Crux, nearby Beta Cruxis and the Jewel Box Cluster. This dark nebula is usually known as the Coalsack nebula. Much like coal itself it could one day ignite as it becomes an active stellar nursery, shining up as one of the brightest sections of our skies.

    Following the Moa's ascent, Scorpius rises in the east. In Maori starlore we know it as the legendary fish hook of Maui. Where the Milky Way bulges, next to Scorpius, is Sagittarius A - the Galactic Centre - where we have the brightest view of our own galaxy. From the Galactic Centre we receive intense radio feedback from the super-massive black hole at the centre of our Milky Way.

    Using the Southern Cross we can find, Canopus, the second brightest true star in our sky. It is part of the Carina constellation, the keel of Argo Navis. The ship that used to dominate the night sky as the largest constellation. In March it is located above the Crux. In the centre of this constellation is the Great Carina Nebula which houses the giant red dying star Eta Carinae. It once illuminated our night sky as one of the brightest stars for a short period of time after it undertook a massive event known as an imposter supernova. Now this hardy star, encased in the Homunculus Nebula, has faded and can only be seen through a telescope.

    The globular star cluster 47 Tucanae will be high in the sky and faintly spotted to the naked eye by the tenth brightest star, the pancake star Achernar (It's spinning so fast it's flattened itself out a bit). Globular clusters are fascinating things. Their structure allows us witness stellar interactions but also allows us to pinpoint the smallest and faintest stars. The large bright stars are at the core while the outer stars are fainter creating a unique and beautifully ordered structure found only in globular clusters.

  • Magellanic Clouds - We can also look for two of our neighbouring galaxies - the Magellanic Clouds. You can see them without the aid of a telescope. But you will need to get away from the bright city lights on a dark moonless night. These two small irregular dwarf galaxies orbit our Milky Way. The gravitational, pull of our galaxy, warps and distorts them - pulling away clouds of dust and gas and even stars to form the Magellanic Stream. The SMC and LMC are actually connecting by a bridge of neutral helium, suggesting they were once the same object. The Magellanic Clouds are the furthest objects away from home that we can see from our backyards in the southern hemisphere.

  • G - That's it for us in the month of March. Thanks for tuning in. J - and we wish you all very happy star gazing.

    Odds and Ends

    In a case of life imitating art, a start-up company called SpinLaunch is pressing ahead with plans to build a centrifuge in a vacuum, and then use that to sling-shot payloads into space. We discuss the feasibility of this for various cargoes, and conclude that this one should not be tried at home.

    On the 6th of February, SpaceX tested their new Falcon Heavy rocket by launching Elon Musk's old Tesla Roadster into orbit around the Sun. We discuss a paper written by Hanno Rein, Daniel Tamayo, and David Vokrouhlicky which looks to see if the car will ever return to Earth by crashing into it!

    Joel talks about pieces of a 50 year old flying saucer that have reappeared in the archives of the London Science Museum. The small flying saucer, which was discovered in 1957, caused great excitement in the British press. Now rediscovered, we take the opportunity to discuss this odd moment in the history of the United Kingdom.

    Show Credits

    News:Shruti Badole
    Interview:Prof. Michael Shara and Luke Hart
    Night sky:Ian Morison and Jasmine Chan-Hyams and Gaby Perez
    Presenters:Nialh McCallum, Josh Hayes and Joel Williams
    Editors:Naomi Asabre Frimpong, Andreea Dogaru, Jake Morgan and Tom Scragg
    Segment Voice:Mike Peel
    Website:Emma Alexander, Jake Morgan and Stuart Lowe
    Producers:Emma Alexander and Jake Morgan
    Cover art:An artist's illustration of an ultra-massive black hole. CREDIT: NASA/CXC/A. Jubett

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