Eyes in the Sky by May Andrew;Clegg Brian;

Author:May, Andrew;Clegg, Brian;
Language: eng
Format: epub
Publisher: Icon Books, Limited
Published: 2023-11-12T00:00:00+00:00

TESS divides the sky into 26 sectors and spends two orbits – around four weeks – observing each in turn.

NASA

Of course, we shouldn’t be so parochial as to imagine that a planet has to be closely similar to our own in order to be worth studying. Astronomer Niall Deacon has likened that attitude to British tourists arriving in an exotic far-flung destination and immediately saying, ‘Let’s find a fish and chip shop.’ In fact, TESS – like Kepler before it – has made plenty of intriguing discoveries that are distinctly non-Earth-like in nature.

Many of TESS’ earliest fully confirmed planets are in this category, for a reason that is fairly obvious if you think about it. The best way to confirm the existence of a planet is to observe multiple different transits – and since we’re going to see at most one transit per orbit of the planet around its host star, that’s going to happen quickest in the case of a planet with a very short orbital period. Since exoplanets follow Kepler’s laws just as much as the Solar System’s planets do, this means the planet needs to be located extremely close to its star – and is therefore almost certainly much too hot to be habitable.

An extreme case of this is the exoplanet Gliese 367b, which was observed by TESS between February and March 2019. During that time, it was seen to make dozens of transits, because its orbital period is an astonishingly short 7.7 hours. In other words, a ‘year’ on Gliese 367b lasts less than a third of an Earth day. This definitely puts it in the ‘interesting’ category – and fortunately, it’s close enough to us, at a distance of just 31 light years, that astronomers can study it in detail. It’s a small planet, somewhere between Mars and Earth in size, and probably has a similar chemical composition to the Solar System’s innermost planet, Mercury. The latter has a reputation for being hot, with a daytime surface temperature up to 430º Celsius – but Gliese 367b is far hotter still, possibly reaching as high as 1,500º Celsius.

TESS has also turned up its own counterpart to the enigma of Tabby’s Star, in the form of a star labelled TIC 400799224 in the TESS input catalogue. This displays a strange pattern of brightness changes that’s distinctly reminiscent of Tabby’s Star, characterised by sudden, very deep dips that are nothing like those expected from a planetary transit. After further investigation, this appears to be not one but two stars orbiting around each other, with one of them – rather like Tabby’s Star itself – surrounded by a dense cloud of dust, or possibly the debris from a shattered asteroid.

Another anomalous light curve belongs to a star called TOI-178, where TOI stands for ‘TESS Object of Interest’. The latter designation means just what it says: the object looked interesting enough on first detection to be added to a list of candidates worthy of follow-up observation by other telescopes. In

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