In the show this time, we talk to Kaustav Basu about The Sunyaev-Zeldovich effect, Cameron Bogue rounds up the latest news, and we find out what we can see in the December night sky from Ian Morison, Haritina Mogosanu and Samuel Leske.
This month in the news: The detection of radio emission possibly caused by an exoplanets magnetosphere, and a mysterious signal that might have come from our closest star system.
Potentially the very first radio emission from an extrasolar planet has been detected in the constellation Boötes by an international team of scientists, who published their findings on December 16th. The system of origin is named Tau Boötes, a binary star system 51 light years away. The exoplanet in question is a so-called ‘hot Jupiter’ – a gas giant that is very close to its host star. The signal was detected using LOFAR, a radio telescope in the Netherlands; In fact, a number of potential exoplanet radio emission candidates were observed, but only the Tau Boötes gave a significant radio signature.
Two years ago, Cornell postdoctoral researcher Dr Jake Turner and his team examined the radio emission of our very own Jupiter and used this data to predict what one might expect to observe from distant Jupiter-like exoplanets. The strength and polarisation of the radio emission detected from this particular exoplanet is indeed compatible with the theoretical predictions made from this earlier research, leading astronomers to believe the signal may have been emitted by the planet itself.
Observing an exoplanet’s magnetic field gives valuable insight into the system – it has implications for the atmospheric properties of the planet, as well as information on its interior and the physics of the interactions it has with its host star. Here on Earth for example, the planets magnetic field is hugely important for life, protecting us, and shielding us from solar winds and cosmic rays – as well as protecting us from atmospheric loss.
It is worth noting however that the signature is fairly weak, and uncertainty remains on whether or not these observations imply what we think they imply; Follow-up observations should hopefully give confirmation, opening up a new way to observe exoplanets.
Next up, staying in the radio regime, another intriguing signal has been detected from the direction of Proxima Centauri. Some listeners may be aware that Proxima Centauri is the closest star to our own Sun - a red dwarf star only 4.2 light years from Earth, incredibly close by cosmic standards, though it is actually too dim to be seen from Earth with the naked eye. This particularly peculiar signal was picked up by the Parkes telescope in Australia last year in fact, but had only recently been investigated, flagged up by Shane Smith, an intern at Berkeley, as part of the Breakthrough Listen project.
The Breakthrough Listen project was launched in 2015, and buys observing time on radio telescopes around the globe to search for intelligent extra-terrestrial life. This pursuit, more commonly known as the Search for Extra-Terrestrial Intelligence (or SETI), looks for “technosignatures”: signals that do not fit with known natural astrophysical processes, but instead could be emission caused by the technology of another civilisation, as is implied by the name.
In order to end up in front of a researcher, any potential technosiganture first has to make it’s way through a number of automated tests, with the aim of eliminating any obvious terrestrial interference (mobile phones, microwaves and such), but even with these tests in place, hundreds of candidates routinely make it through, so there is plenty to look at. It was tasked to Shane Smith, an undergraduate intern, to examine data taken by the Parkes telescope originally used to observe Proxima Centauri for 26 hours as part of a stellar flare study. It was in late October of this year that he spotted something strange – very sharp narrowband emission at around 982 megahertz. Sofia Sheikh, who led the ensuing analysis said that this is the most exciting signal found from the Breakthrough Listen project thus far – the signal has since been dubbed BLC1, for “Breakthrough Listen Candidate 1”.
So what do we know about Proxima Centauri? At least two planets are known to orbit the star - the first was discovered in 2016, named Proxima b, and is very close to the red dwarf. It is around 1.2 times Earth’s size, and has an 11 day orbit. Even though the planet is so close to the star, it is still part of the habitable zone (the region around a star in which liquid water could exist on the surface of a rocky planet), as Proxima Centauri is much cooler than our sun. The second planet, roughly 7 times the size of Earth, named Proxima c, was found in 2019, much further from the star in a 5.2 year orbit.
Of course, neither of these planets would be conducive to human life, and there are a number of reasons why researchers remain very sceptical of the signal thus far – for Proxima b in the habitable zone, it’s close proximity to it’s host star bathes it in radiation; solar flares unleashed from Proxima Centauri would easily strip-away an earth like atmosphere, as shown by Nasa scientists in 2017. Indeed, as stated earlier, the original study with the Parkes telescope was set to inform researchers on how solar flares could affect the stars planets. Proxima b is also tidally locked, one side being in eternal day, and the other in eternal night. Furthermore, the statistical probabilities of finding two forms of intelligent life so close together (around our sun, and around our closest neighbour) whilst not detecting life anywhere else thus far is incredibly low.
For now, months of further analysis of are yet to come, and while astronomers are almost certain this will not turn out to be extra terrestrial intelligence, they hoped to be proved wrong, and either way, this certainly remains one of the most interesting signals found by Breakthrough listen to date.
Interview with Kaustav Basu
Dr Kaustav Basu of the Argelander institute, Bonn, talks about the Sunyaev Zeldovich effect. He discusses what we can learn from measuring the effect, in particular for cosmology.
The Night Sky
Ian Morison tells us what we can see in the Northern Hemisphere night sky during December 2020.
- Jupiter, along with Saturn, still remains visible, low in the sky, west of south when darkness falls as December begins and sets around 19:00 GMT. Towards the end of the month it will be seen towards the southwest after sunset and sets by ~17:30 GMT. Its magnitude remains at -2.0 during the month whilst its angular diameter falls from 34.4 to 32.9 arc seconds. Sadly, even when first seen after sunset, it will only have an elevation of ~12 degrees above the horizon so the atmosphere will limit our views. Due its position in the most southerly part of the ecliptic this has been a very poor apparition for those of us in the northern hemisphere.
- SaturnClosely follows Jupiter into the sky, some 2 degrees behind at the start of the month but reducing to just 6 arc minutes on the evening of the 21st! [See highlight above.] Saturn is best seen in the south just after sunset on the 1st. Its magnitude remains steady at +0.6 whilst its angular size decreases from 15.7 to 15.3 arc seconds. The rings span some 35 arc seconds across and, at ~22 degrees to the line of sight, show up well. Saturn starts the month in Sagittarius and moves into Capricornus on the 15th. Sadly again, its low elevation of ~12 degrees when first visible in the evening will limit our views of this most beautiful planet.
- Mercury will be visible using binoculars very low in the southeast at dawn for the first few days of the month. On the first, it rises only 45 minutes before the Sun shining at magnitude -0.8. It will pass through superior conjunction (closest to the Earth) on the 20th of the month. Please do not use binoculars after the Sun has risen.
- Venus, rises in the southeast some 2 hours before the Sun at the star of December but by half an hour less by month's end. Its magnitude remains at -3.9 throughout the month whilst its angular size reduces from 11.7 to 10,7 arc seconds. At the same time its phase, the percentage illuminated disk, increases from 89% to 94% which explains why its magnitude remains constant.
- Early December - still a good time to view Mars.This is still a good month to observe Mars which had its closest approach to Earth back on October the 6th when it will lay 39 million miles from Earth and reached opposition on the 13th. Wonderfully, at this opposition, Mars has been far higher in the sky than at recent oppositions. In Pisces, Mars, shining at a magnitude of -1.1 at the start of the month, can be seen crossing the meridian at 20:30 GMT. By month's end it magnitude will have dropped to -0.3 whilst being due south at ~19:15 GMT. Its angular size is just over 14 arc seconds at the start of the month dropping to 10.5 arc seconds by month's end. Reaching an elevation of ~45 degrees when due south as seen from the UK, amateur telescopes will enable one to see features, such as Syrtis Major, on its surface when the seeing conditions are good.
- December 14th and 15th after midnight: the Geminid Meteor Shower.The early mornings of December 14th and 15th will give us the chance, if clear, of observing the peak of the Geminid meteor shower. The Moon is new so, pleasingly, its light will not hinder our view. The Geminids can often produce near-fireballs and so the shower is well worth observing if its clear. An observing location well away from towns or cities will pay dividends. The relatively slow moving meteors arise from debris released from the asteroid 3200 Phaethon. This is unusual, as most meteor showers come from comets. The radiant - where the meteors appear to come from - is close to the bright star Castor in the constellation Gemini as shown on the chart. If it is clear it will be cold - so wrap up well, wear a woolly hat and have some hot drinks with you.
- December 21st - after sunset - The closest visible conjunction of Jupiter and Saturn since 1226!After sunset on the 21st of December, let us hope for clear skies as Saturn and Jupiter will be at their closest in the sky since the middle ages at just 6 arc minutes apart! This means that with a telescope at moderate power one would be able to encompass both planets and their brighter satellites; Io Europa, Ganymede and Callisto with Jupiter and Titan with Saturn.
- December 22nd/23rd - late evenings: the Ursid Meteor ShowerThe late evenings of the 22nd and 23rd of December are when the Ursid meteor shower will be at its best - though the peak rate of ~10-15 meteors per hour is not that great. Pleasingly, this year the first quarter Moon Moon will set around midnight so its light will not greatly hinder our view. The radiant lies close to the star Kochab in Ursa Minor (hence their name), so look northwards at a high elevation. Occasionally, there can be a far higher rate so its worth having a look should it be clear.
- December - evening: the Double Cluster and the 'Demon Star', Algol.This month, in the evening, is a good time to look high in the south towards the constellations of Cassiopea and Perseus. Perseus contains two interesting objects; the Double Cluster between the two constellations and Algol the 'Demon Star'. Algol in an eclipsing binary system as seen in the diagram below. Normally the pair has a steady magnitude of 2.2 but every 2.86 days this briefly drops to magnitude 3.4.
- December: find M31 - The Andromeda Galaxy - and perhaps M33 in TriangulumAround new Moon (14th December) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting!
- December 12th - 1 hour before sunrise - Venus and a thin crescent Moon.Before dawn on the 12th of December, Venus will be seen, if clear, down to the lower left of a very thin crescent Moon. Look out for the 'dark' side of the Moon illuminated with light reflected from the Earth - 'Earthshine'.
- December 17th - after sunset - Jupiter, Saturn and a thin crescent MoonAfter sunset on the 17th of December, Saturn and Jupiter will be seen, if clear, to the right of a very thin crescent Moon. Look out for the 'dark' side of the Moon illuminated with light reflected from the Earth - 'Earthshine'.
- December - Evenings of the 7th and 23th: The Straight WallThe Straight Wall, or Rupes Recta, is best observed either 1 or 2 days after First Quarter or a day or so before Third Quarter. To honest, it is not really a wall but a gentle scarp - as Sir Patrick has said "Neither is it a wall nor is it straight!"
- The evening sky in December is commandeered by the edge of our galaxy, visually in the asterisms of Orion and Taurus. The region in question is so beautiful that it simply demands all attention. However, the entire December sky is shattered with bright planets and bright stars at dusk.
- In December, Jupiter and Saturn will be very close, as they near their once-in-20-years conjunction on December 21-22nd, 2020. At their closest, they will be only 0.1 degrees apart. That’s just 1/5 of a Full Moon diameter. They will be in close visual proximity from December 17th to the 26th. When two bright objects in the sky are in the same line of sight, we call the phenomenon a conjunction. Every twenty years, Jupiter, orbiting the Sun in 12 years, catches up with Saturn, which takes 30 years to do an orbit. Of course, a conjunction is a visual illusion. In reality, Jupiter is 879 million km away and Saturn 1,610 million km away, mid-month, almost twice further away from the Sun. From Wellington, it would be a bit tricky to photograph or see the two objects through a telescope on the 21st of December but if you observe them at 9PM when it is not yet night, they will be at about 15 degrees above the horizon. Try and find a place with a clear horizon. Otherwise, they will simply be two bright dots visible in the west after sunset.
- Another beautiful visual combination is the line that the brightest star Sirius makes with the Second brightest star, Canopus. Extend that line south and you will come across the Large and the Small Magellanic clouds. This is a very good trick to find our beautiful southern dwarf irregular galaxies in the night sky. From a dark sky, the Large Magellanic Cloud looks like a chunk of the Milky Way has been displaced nearby.
- The Southern Cross and the pointers are very low on the Southern horizon, making the asterism of the frying pan. The two pointers are the handle of the pan, and Epsilon Centauri (Birdun), Gamma Centauri (Muhlifain) and Delta Centauri (SAO 239689) are the frying pan. The Southern Cross is the fish frying in the pan. Close to the Southern Cross, the dark region of the Coalsack for Maori is the flounder also frying in the frying pan. Our gastronomical sky also contains the Pot, in Orion, with the bottom of the pot made by the three stars of Orion’s belt and the handle of the pot constructed from the metal of Orion’s sword. The pot is held in place by Eta Orionis.
- This is the best time of the year to observe our famous southern sky galaxies, the magellanic clouds. The first person to write about them, was the Persian Astronomer Al-Sufi around 964 AD. Explorer Amerigo Vespucci, in a letter about his third voyage around 1503 - 1504 was the next to write about the Magellanic Clouds and also about the coalsack, referring to them as the three “Canopes”, two bright and one obscure. And finally, Ferdinand Magellan wrote about it after his voyage in 1519. To spot the Magellanic clouds, you need a very dark sky and use your peripheral vision. With a telescope, the Large Magellanic Cloud is an amazing sight. One of my favourite deep sky objects, 30 Doradus or Tarantula nebula is a cloud of partially ionized gas in which star formation has recently taken place. Just like the horsehead nebula in Orion, the Tarantula Nebula in the Large Magellanic Cloud is a place where thousands of stars can form over a period of several million years. Supernova 1987a—the nearest supernova in recent years, co-discovered by New Zealand astronomer and Guinness book record holder Albert Jones, —was in the Large Magellanic Cloud. For regions like the Tarantula Nebula, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases, now easily visible in telescopes, leaving behind a cluster of stars which have formed. We can see what happened to such stars when we look at the starcluster the Pleiades.
- Close to Zenith is Achernar from Eridanus, all the beautiful stars of Grus and Fomalhaut. In Grus, the Grus Quartet is now visible. In Sculptor, the famous Sculptor galaxy is in a good position to observe. This galaxy has a visual magnitude of about 7 and it is visible with the naked eye, it looks like a blurred star. Sculptor galaxy is about 12 million light years away from us.
- A total solar eclipse will be visible from South America on the 15th of December as the New Moon disappears into the Sun’s glare. There will also be a few minor meteor showers, the geminids and leonids, nothing that compares with the northern Hemisphere’s perseids in August. Mercury will pass around the far side of the Sun on December 20th and on the 21st we will have the longest day of the year, the summer solstice.
Highlights of the Month
Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during December 2020.
Odds and Ends
The Moon is on people’s minds again, as various states and private companies look towards its resources and potential sites for science. A recent paper published in the Philosophical Transactions of the Royal Society outlines these competing interests, and how they might potentially clash in the coming years. The authors also make recommendations on how to avoid these problems, including establishing common goals and infrastructure early on, in order to avoid the Moon becoming a new sphere of human conflict.
We also have a christmassy discussion on what the wise men from the christmas story could have seen in the night sky.
We discuss the recent distance verification of the oldest galaxy we know of. The measurement was made using the Keck 1 telescope by a team at the university of Tokyo and measured the age of and distance to the GN-z11 galaxy
|Interview:||Kaustav Basu and Michael Wright|
|Night sky:||Ian Morison and Haritina Mogosanu|
|Presenters:||Jake Staberg Morgan, Imogen Towler and Amy Suddards|
|Editors:||Michael Wright, Tom Scragg and Hongming Tang|
|Segment Voice:||Tess Jaffe|
|Website:||Michael Wright and Stuart Lowe|
|Cover art:||A gibbous Moon taken from Denmark on 2008-08-18, 00:20. Handhelt shot (Canon EOS 400D, Sigma AF 150-500mm f/5-6.3 DG APO HSM OS, 500 mm, f = 8, 1/400 sec., ISO 400). HDR technique used. CREDIT: From Wikimedia Commons, the free media repository|