Tag Archives: Cheops

CHEOPS observations of WASP transits

CHEOPS, the CHaracterising ExOPlanet Satellite is ESA’s Small-class mission dedicated to recording transits of exoplanets. A new paper led by Luca Borsato presents some early observations of transits of WASP, KELT and HATnet planets.

Here, for example, are the lightcurves of two transits of WASP-8b, both plotted against phase.

The paper focuses on the transit timing, which can be as good as timing a transit to an accuracy of 13 to 16 seconds, depending on the brightness of the host star and the amount of transit covered by the observations.

One aim of such work is to look for variations in the timing of transits, caused by the gravitational perturbations of additional unseen planets in the system.

First results from ESA’s Cheops: WASP-189b

ESA’s Cheops satellite (the Characterising Exoplanet Satellite) started observing this year, and ESA has just put out a press release announcing its first science results. Cheops looked at transits and occultations of WASP-189b, an ultra-hot Jupiter in a polar orbit transiting a bright star.

“Only a handful of planets are known to exist around stars this hot, and this system is by far the brightest,” says Monika Lendl of the University of Geneva, Switzerland, lead author of the new study. “WASP-189b is also the brightest hot Jupiter that we can observe as it passes in front of or behind its star, making the whole system really intriguing.”

At a visual magnitude of V = 6.6, WASP-189 is the brightest host star of all the WASP planets. The discovery of the transiting hot Jupiter was announced in 2018 in a paper led by David Anderson. The exceptional nature of WASP-189 thus made it a prime target for Cheops.

The Cheops study shows that: “the star itself is interesting – it’s not perfectly round, but larger and cooler at its equator than at the poles, making the poles of the star appear brighter,” says Dr Lendl. “It’s spinning around so fast that it’s being pulled outwards at its equator!”

“This first result from Cheops is hugely exciting: it is early definitive evidence that the mission is living up to its promise in terms of precision and performance,” says Kate Isaak, Cheops project scientist at ESA.

Press coverage has included articles in CNN, CTV, the International Business Times, The Sun, The Mirror, The Daily Mail, The Express and over 30 other news sites.