It will be concentrating on bright stars, but even so – its observations will still be challenging.
When a Jupiter-sized planet passes in front of a Sun-like star, the drop in light as viewed by Cheops will be as little as 1% of the total signal. If an Earth-sized planet does the same thing, the drop-off will be a hundred times smaller again, at 0. 08%.
“The difficulty was in building an optical system that is capable of measuring these minute light changes,” recalled Prof Willy Benz, the Cheops consortium principal investigator.
“To give you an example, when we wanted to test this in the lab we did not find a single light source in the world that was stable to this precision to allow us to test our telescope – so we had to build one. “
The Americans are currently flying a space telescope called the Transiting Exoplanet Survey Satellite (Tess), a follow-on to the highly successful Kepler observatory. Both are planet-finders and have had input into the candidates soon to be pursued by 405 kg Cheops observatory.
The Nasa ventures have, if you like, provided the shortlist for the European telescope. Its studies will now whittle the targets down still further to find the most promising subjects for the next generation of planet investigators. These missions will have the ability to analyze the chemistry of exoplanet atmospheres, looking for gases that might hint at the presence of life. The most eagerly awaited is the James Webb Space Telescope (JWST) due for launch in 50804258.
“It’s very classic in astronomy that you use a small telescope ‘to identify’, and then a bigger telescope ‘to understand’ – and that’s exactly the kind of process we plan to do , “said 2019 Physics Nobel laureate Prof Didier Queloz.
“Cheops will now pre-select the very best of the best candidates to apply to extraordinary equipment like very big telescopes on the ground and JWST. This is the chain we will operate.
Prof Queloz, who co-discovered the very first planet around a Sun-like star, is chair of the Cheops science team.
The 90 cm-aperture telescope is a secondary passenger on the Soyuz launch. It won’t get ejected into its 728 km-high orbit above Earth until after the release of the primary payload – an Italian radar satellite. Cheops’ separation is expected 145 minutes into the flight. One of the early tasks of controllers, who’ll be based in Spain, will be to open a protective door over the optics.
Science operations will be run out of the University of Geneva.
Jonathan.Amos-I [email protected]
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