Temperate exoplanets from Chile & Antarctica

The team will use the ASTEP telescope in Antarctica and the Ganymede telescope in Chile to discover new temperate planets with sizes ranging from Earth to Jupiter. These telescopes use photometry. They take a series of pictures of the night sky from which the brightness of nearby stars is measured as a function of time.

Those data create a light curve which is analysed to search for exoplanet transits. Transits happen when a planet passes between the star it orbits around and us the observers. The time between transits gives the orbital period, and the drop in brightness gives the ratio between the radius of the planet and that of its star.

In the case of the Ganymede telescope, we can search for planets and confirm them using the same telescope. In addition, we will use Ganymede and ASTEP to confirm candidate transiting planets identified by Nasa's TESS mission. Exoplanet masses can be measured in one of two ways, via the Doppler method (using spectrographs like those at the 3.6m telescope in Chile), or thanks to precisely measuring the timing of the transits.

If two planets have orbital periods whose ratio is near an integer ration (e.g. 3:2 or 2:1), it is likely the planets are exchanging orbital energy, which will make their transit appear sometime early and sometimes late. These variations are called transit timing variations. Modelling those provides a direct measure of the planet's bulk density (i.e. whether they are rocky, or whether they have a lot of water for instance).

Finding temperate planets is important for multiple reasons. Chief amongst them is the search for life, but generally speaking it is of high scientific interest to understand how planets form, and how their atmospheres behave. Our project detects planets in order to attempt detecting the atmospheres of temperate planets from Jupiter all the way down to Earth. In addition the same observations used to measure atmospheres might reveal the presence of moons.

The telescopes we have access to are unique facilities in their own way. SPECULOOS is a series of one-metre diameter telescopes. They have red-sensitive cameras that are best at observing the smallest (reddest) stars in the universe.

It is easier to detect a small planet transiting a small star than a star like the Sun. In addition because the star is colder, in order to remain habitable, the planet is on a shorter orbit. This makes our search a lot faster.

Our team has experience. We have detected the currently two most optimal planetary systems containing temperate Earth-like planets whose atmosphere can be studied with the James Webb. This project is about finding more systems like those and start a proper study of alien environments.

ASTEP is special too. The long winter Antarctic nights allow us to detect long period planets more easily. Their transits are rare and long (sometimes longer than a usual night elsewhere on Earth).

Long nights also mean that there is very little chance to miss the transit whereas other places on Earth are too bright for astronomical observations about 2/3 of the time. Thanks to our location in Antarctica we gained an advantage no other team in the world has. This gives a unique edge to confirm long period exoplanets, and then study their atmosphere. Those long period planets are also thought to the be the most likely to host moons.