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December 2017: Neighbourhood Watch

December 2017

In the show this time, we talk to Dr. Romain Tartese about the upcoming PROSPECT lunar mission, Jake Morgan rounds up the latest news, and we find out what we can see in the December night sky from Ian Morison and Claire Bretherton.

The News

Our first story this month comes from our own solar system - but began outside it. A passing asteroid named 'Oumuamua, which loosely translates from Hawaiian as "a messenger from afar arriving first", has been confirmed as the first catalogued interstellar asteroid, receiving the new designation of 1I/2017 U1, with the I standing for "Interstellar". The asteroid was first detected on October 19th by the University of Hawaii's Pan-STARRS 1 telescope sited at Hawaii, as it scanned the sky to search for near-Earth objects for NASA. The agency is keen to find and track such Near-Earth Objects, or NEOs, with a particular eye to identifying any that make close approaches, or could potentially be hazardous to us here on Earth. Calculations initially suggested it might be an interstellar interloper, and a combination of archival and follow-up observations from an array of telescopes, including the VLT in Chile, have confirmed that the object is interstellar in origin. The recovered light curves indicate the object is up to 200 metres long and spins once every 7.3 hours. Also notable is the object's high aspect ratio - it is up to 10 times longer than it is wide, giving it a pencil or cigar-like shape. Objects of this nature are not observed in our own asteroid belt. Despite making a close approach to our Sun, 'Oumuamua has no trail of ice or dust associated with it, ruling out the possibility of it being a comet.

The confirmation paper has been published in Nature, and efforts are ongoing to try and identify where this visitor might have come from. However, such efforts are complicated by the fact that we don't know how long the asteroid has been travelling for before it reached us, making an exact determination difficult. After following a steep trajectory toward the inner solar system,'Oumuamua is now on the outbound leg of its orbit, travelling at 38 kilometres per second relative to the Sun. This speed is too fast for any current craft to catch up and land on it, as was done with comet 67/P, but observations are ongoing as it heads towards the constellation Pegasus, on the next leg of its journey.

Moving further afield, the High Accuracy Radial velocity Planet Searcher (HARPS) team at the La Silla Observatory in Chile has found that a nearby red dwarf star, designated Ross 128, is orbited by a low-mass exoplanet with an orbital period of 9.9 days. This Earth-sized world is expected to be temperate, with a surface temperature that may also be close to that of the Earth. At 11 light-years distance, Ross 128 is the "quietest" nearby star to host such a temperate exoplanet.

Our closest stellar neighbour, Proxima Centauri, is also known to host a planet, leading to intense media speculation about whether it could potentially be habitable. However, many red dwarf stars, including Proxima Centauri, are active objects, producing flares that occasionally bathe their orbiting planets in intense ultraviolet and X-ray radiation, potentially stripping the atmospheres from any orbiting companions and rendering them uninhabitable. However, it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life. With the data from HARPS, the team found that Ross 128b orbits at a distance of 0.05AU, 20 times closer than the Earth orbits the Sun. Despite this proximity, Ross 128b receives only 1.38 times more irradiation than the Earth, thanks to its much smaller parent star. As a result, Ross 128b's equilibrium temperature is estimated to lie somewhere between -60 and +20 degrees Celsius, again thanks to the cool and faint nature of its small red dwarf host star, which has just over half the surface temperature of the Sun. While the scientists involved in this discovery consider Ross 128b to be a temperate planet, uncertainty remains as to whether the planet lies inside, outside, or on the cusp of the habitable zone; the region where liquid water can exist on a planet's surface.

Astronomers are now detecting more and more temperate, Earth-sized exoplanets, and the next stage will be to follow up these discoveries, studying their atmospheres, composition and chemistry in more detail. In particular, the detection of biosignature gases, such as molecular oxygen and ozone in the closest exoplanet atmospheres will be a significant next step, as spectroscopy is typically confined currently to larger hot-Jupiter and super-Neptune type planets. To access super-Earths and potential Earth-analogues, the new generation of telescopes and spectrographs will be needed, such as the ESPRESSO spectrograph suite at the VLT, due to start operations next year, the ESO's Extremely Large Telescope currently under construction, and the James Webb Space Telescope, currently undergoing testing and final construction in the United States. Watch this space!

And finally, returning to Earth, the Arecibo Observatory in Puerto Rico looks set to get a new lease of life, as the National Science Foundation has announced that it will seek funding partners to keep the radio telescope in operation and aimed at the cosmos. We first reported on this story here at the JodCast in February, when the NSF first announced it was in need of financial partners to keep the radio telescope running. Faced with a dwindling budget for the telescope, the NSF has been seeking to transfer control of the Arecibo Observatory to a university or third party institution. The divestment options also included demolition of the observatory, naturally drawing the ire of scientists who use the facility built into a natural depression near the town of Arecibo, Puerto Rico. It made the news again in October, when the territory was struck by the Category 5 hurricane Maria. Some of the telescope's dishes and surface tiles were damaged, but all staff were unharmed, and limited scientific operations have since resumed. If new partners or operators can be found, they will be able to take on the task of restoring full functionality and keeping Arecibo's eyes on the sky.

Interview with Dr. Romain Tartese

Max Potter sits down with Dr. Romain Tartese from the University of Manchester's Earth Sciences department to discuss his involvement in the upcoming PROSPECT lunar mission. Set to fly in 2022, this ESA mission will assess both the nature and quantity of water ices and other volatiles on the surface of our Moon; resources which could be of vital importance in future space exploration.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during December 2017.

The Planets

Wishing you clear skies and a Merry Christmas from the team here at Space Place at Carter Observatory.

Odds and Ends

In a post-fact world where a man can put together a homemade, steam-powered rocket to fire himself into the air to show that the Earth is flat, we take a quick look at some simple proofs for the Earth being round, as well as discussing how we have ended up in the position where people are tired of experts and decide which bits of scientific fact they want to believe.

Iridium flares are to (mostly) cease by the end of 2018, Iridium Communications confirmed to BBC Sky At Night magazine. A popular target for many astronomers, Iridium flares are caused by 66 mobile satellite communications satellites in low Earth orbit. They all have three highly reflective antenna panels, which can reflect sunlight and cause the predictable brightening of the satellite for between 5-20 seconds, and up to a magnitude of -8. They are currently being replaced with a new fleet of satellites, which will no longer cause the flares, and the old satellites have started to be de-orbited. There are many applications that track when an Iridium flare is due to occur, so catch them while you can!

Nialh discusses some top-quality click-bait, which asks, "Are we the aliens we seek?". We discuss the possibility of bacteria hitching a ride on interstellar dust thrown up by collisions, the importance of conducting clean space missions... and pineapple juice.

Show Credits

News:Jake Morgan
Interview:Dr. Romain Tartese and Max Potter
Night sky:Ian Morison and Claire Bretherton
Presenters:Emma Alexander, Josh Hayes and Nialh McCallum
Editors:Naomi Asabre Frimpong, Joseph Kwofie, Jake Morgan and Tom Scragg
Segment Voice:Iain McDonald
Website:Jake Morgan and Stuart Lowe
Producer:Jake Morgan
Cover art:An artist's impression of the first confirmed interstellar asteroid, 1I/2017 U1. CREDIT: ESO

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