Cheops space telescope
​​CHEOPS belongs to a family of space telescopes within the Eu​ropean Space Agency (ESA) programme Cosmic Vision. Together with its larger siblings PLATO, to be launched 2028, and ARIEL (2028), CHEOPS will increase our knowledge of other planetary systems. ​​​
​​​ESA/ATG medialab

Cheops: new satellite to study exoplanets in detail

​​The satellite CHEOPS, launched in December 2019, will observe systems with previously known exoplanets – planets which orbit other stars than the sun – in order that we can learn more about their size, composition, and atmosphere. The project is led by Nobel laureate Didier Queloz, who will visit Chalmers on 13 December.
At Chalmers, Carina Persson and her colleagues are preparing to receive and analyse the huge amounts of data that the satellite will deliver. 

 
“We previously believed that all systems looked more or less like ours. But the first exoplanet found by Queloz and Mayor was a Jupiter-like planet, that orbits so close to its star that its orbital period is only four days – which was very surprising,” says astronomer Carina Persson.

 
“CHEOPS will take us a step closer to answering whether our planetary system is unique in the universe. Perhaps it is really uncommon for a medium size planet such as ours to form, at just the right distance, from a star of just the right type, with the right sorts of planets around, and in the right place in the galaxy.”

 
There are two main techniques for finding and studying exoplanets. The technique which was awarded the 2019 Nobel Prize measures small, regular changes in a star’s speed, which can be measured from Earth when a planet orbits the star. The technique has been used to discover many planets, and researchers can derive information on a planet’s mass, and distance from its host star. 

 
The CHEOPS satellite will use another technique, transit photometry, to observe how a star’s light changes 
when a planet passes in front of it.  

 
“The advantage with CHEOPS is that we already know which planets it will investigate, and what their orbits look like. So, we know exactly where and when we should point the telescope, in order to capture several transits from the same planet,” says Carina Persson, who works closely together with colleagues Professor Malcolm Fridlund and PhD Student Iskra Georgieva.

 
“In general, measurements like this which have been made so far have come with large uncertainties. With CHEOPS, the precision will increase significantly. We will be able to measure the planet’s size with high accuracy, look for moons and rings and maybe even draw conclusions about what kind of atmosphere they have. If we add that to what we already know about them, we can make models of the planets’ compositions to find out if they are Earth-like or gas planets. The results can also be used to model how planets form and evolve.”

 
The three Chalmers scientists have tested and developed software with algorithms which will analyse transiting exoplanets recorded in CHEOPS’ measurements. 

 
“There are so many factors that decide how planets form, and so far, we only know of one planet which supports life. The more you study other planets, the more respect you feel for our planet and life on Earth. I think that is one of the most important aspects of our work,” says Carina Persson.  

Text: Christian Löwhagen
This article was originally published in Swedish in Chalmers magasin, 2019 nr 2. 

Published: Tue 21 Jan 2020.