Centre for Exoplanet Science

Detecting and characterising exoplanets

How we find and characterise planets around other stars.

A number of researchers in the centre are involved in projects aimed at detecting and characterising planets around other stars (more commonly known as extrasolar planets, or exoplanets).  We're part of the HARPS-N consortium.  HARPS-N is a high-accuracy spectrometer that uses the radial velocity, or Doppler Wobble, method to indirectly detects planets via the motion of the host star.  A key goal of the HARPS-N consortium is to follow up exoplanets first detected by NASA's Kepler satellite.  Combining Kepler and HARPS-N data allows us to determine the density and, hence, internal compostion of exoplanets.  To date, a large fraction of known rocky planets with accurate mass estimates have been characterised by the HARPS-N team.  All of these rocky planets are, however, orbiting very close to their parent stars and are, therefore, far too hot to be potentially habitable.

We are also involved in directly detecting exoplanets using NACO and SPHERE.  Currently, we are only able to directly detect massive exoplanets and brown dwarfs (substellar objects with masses between that of a planet and a star) on wide orbits but we are starting to be able to map the surfaces of some of these objects.  The figure below shows a surface map of Luhman 16B, the closest known brown dwarf (Crossfield et al. 2014).

Luhman 16B (credit: ESO/I. Crossfield)
Surface map of Luhman 16B (Credit: ESO/I. Crossfield)

We are therefore currently able to determine the compostion of rocky planets orbiting very close to their parents stars and can map the surfaces of massive planetary bodies on wide orbits.  The next generation of instruments, however, will allow us to detect rocky planets further from their host stars and will allow us to map the surfaces of lower-mass bodies on closer orbits.  All of this is moving us closer to being able to characterise rocky planets orbiting their stars in regions where liquid water might exist and, hence, that may be able to support life.