TESS and iREx: a great synergy for exoplanetary system studies

Wednesday the 18^th of April at 18h51 saw the launch of the space satellite TESS (Transiting Exoplanet Survey Sattelite) on board of a SpaceX Falcon 9 rocket. TESS is the successor of the Kepler Space Telescope, which has already allowed for over 2300 exoplanets to be discovered since 2009. The success of this launch was of momentous importance for the researchers at the institute for research in exoplanets (iREx) who have made a promise to closely study these new systems that will be discovered by TESS.

Searching for the exoplanets that are closest to home

TESS and Kepler are two space telescopes that are not only similar in appearance, but also in functionality. Both were designed to detect exoplanets using the transit method, which is an indirect detection method that consists of measuring the tiny variations in luminosity that occur in a star when an exoplanet passes in front of it. A key difference however is that, while Kepler discovered over 2300 exoplanets by only observing a small region of the celestial sphere, TESS will be charged with watching the near totality (90%) of the sky. On the technical side, TESS can be thought of as Kepler’s little sister since its 10 cm aperture is 10 times smaller than that of its predecessor. The targets it will observe are much closer however, with TESS focusing its efforts on stars less that 650 light years away. In particular, TESS will concentrate on the 1000 nearest M-dwarfs in the solar neighborhood with the objective of discovering Earth-like planets (Super-Earths and/or mini-Neptunes) less than 100 light years away. Professors René Doyon (University of Montreal) and Jason Rowe (Bishop’s University) are part of the TESS team that will follow up these new planetary systems using ground and space based instruments.

The Sun, the Earth, and a small red M dwarf, to scale. (Credit: NASA)

« TESS will provide a vast overview of all the nearest transiting planetary systems which will allow for the study of their atmospheres – a key step towards finding extraterrestrial life», affirms with enthusiasm René Doyon, director of iREx.

Rocky or gaseous planets?

The transit method directly gives us the means to determine the radius of the exoplanet. This precious piece of data can then be combined with another essential quantity: the mass. While not directly deducible from TESS, the mass of an exoplanet can be obtained using the radial velocity method. This complementary detection method infers the presence of, and provides a velocity and mass measurement of, an exoplanet by measuring the wobble that it induces on the star that it orbits. These mass measurements will be obtained using two unique and very high-resolution infrared spectrographs named SPIRou and NIRPS. These spectrographs were designed by the Observatoire du Mont-Mégantic (OMM) in collaboration with other national (NRC-Herzberg, Royal Military College, University of Western Ontario, University of British Columbia and McGill University) and international institutes (l’Observatoire de Genève, l’Institut de recherche en astrophysique et planétologie de Toulouse, l’Observatoire de Grenoble, l’Observatoire de Marseille, the Canada-France-Hawaii Telescope and the European Southern Observatory).

As they have unique and privileged access to SPIRou and NIRPS data, iREx researchers will be at the forefront of the research that will be made on the exoplanets that TESS will find. Once the mass and diameter of an exoplanet are known, the bulk density can then be inferred and used to discover whether said exoplanet is of rocky (high density) or gaseous (low density) nature. Together, SPIRou and NIRPS will receive over 1000 nights of guarantied observation time, over a third of which will be dedicated to newly discovered TESS targets.

Probing the atmosphere of exoplanets with JWST

But this is not the end of the story for iREx and its researchers! Highly involved in the development of the James Webb Space Telescope (JWST) through the principal investigator of one of its 4 scientific instruments, director of iREx and OMM René Doyon, the researchers of iREx will use the Webb telescope to discover whether these exoplanets have atmospheres, and what they are composed of. This difficult and delicate task will be made possible because of JWST and its Canadian instrument NIRISS, which was specially designed for studying exoplanetary atmospheres. iREx researchers will have access to 200 hours of guarantied time with Webb to study the atmospheres of all sorts of planetary systems, including some that are similar to the Earth. These observations will start approximately 6 months after the launch of the telescope, which is scheduled for spring 2020.