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December 2020: 2020 Is Over

December 2020

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.

The News

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

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during December 2020.

The Planets

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