Kepler’s Successor

Recently NASA selected the next set of missions for the Explorer Program to be launched in 2017 from four proposed  mission concepts. The two winning missions were the Transiting Exoplanet Survey Satellite (TESS) and Neutron Star Interior Composition Explorer (NICER).

In some ways you can think of TESS as Kepler’s successor but while it will be monitoring stars for the drop in light due to transiting exoplanets like Kepler,  it’s mission is slightly different. Unlike Kepler which stares continuously at 1 field for it’s entire mission, during TESS’s 2 year primary mission, it will stare at a patch of sky for a short period of time and then move on to examine new stars. In total TESS will survey ~45,000 square degrees of sky, ~400 times larger than the region Kepler monitors.

TESS will target the brightest stars (G-K and M stars) in the sky, much brighter (and therefore closer to the Earth) than the Kepler field stars.  TESS will therefore probe the frequency and properties of  planetary systems that are in the solar neighborhood, and provide a catalog of the closest planet-hosting stars to be followed-up for many years to come.

One of the exciting things about TESS is that the vast majority of the stars it monitors will be prime candidates for current ground-based radial velocity instruments like HIRES (which has been used to help study Planet Hunters planet candidates), HARPS-N, and HARPS-S. This means for the vast majority of TESS planet candidates, we should be able to get masses or constraints on their masses. This is really important because the transit technique gets you a measure of the radius of the planet (if you know the radius of the star). If you can get the mass from radial velocity measurements, then you’ve got yourself the bulk density of the planet. You can think of bulk density as a proxy for composition, and so there will be a large sample of planets to examine how their size and composition compare to that of the planets in our Solar System. In addition, TESS planet host stars will be prime target for studies with the in-construction James Webb Space Telescope (JWST, a space-based infrared telescope scheduled for launch in 2018), that will enable study of the chemical composition of the atmospheres of many of TESS-discovered planets.

Just like Kepler, I think TESS will open a new era in the search and characterization of exoplanets. I think there is a place for Planet Hunters in the TESS age, and I hope that in the future  we’ll be able to share TESS light curves on the Planet Hunters website. You can learn more about TESS here.

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