TESS, the Planet Hunter

The hunt for exoplanets continues! The number of discovered exoplanets has now reached over 4000, yet there are many more waiting to be unveiled. TESS, a NASA mission, will probe the stars closest to the Sun to find new worlds. Its first scientific data release has highlighted a handful of new exoplanets as well as hundreds of new candidates.

What is TESS?

TESS (Transiting Exoplanet Survey Satellite) is a small space telescope that launched about a year ago in April 2018. Much like its predecessor Kepler, TESS will identify exoplanets using the transit method, where variations in luminosity that occur in a star when an exoplanet passes in front of it are detected. Data collection began in July 2018. During its first year of operations, TESS will study the Southern sky, while it will observe the Northern hemisphere during its second year. The first batch of data made available to the scientific community was released in December 2018 and includes data from 2 of the 13 sectors of the Southern hemisphere

A picture of TESS’s first light. We see here the Large Magellanic Cloud (right) and the bright star R Doradus (left). (Credit: NASA/MIT/TESS)

Predictions

TESS’s goal is to discover new planets around the brightest stars close to the Sun. It is expected that TESS will able to find over 10,000 exoplanets. With its continuous observing mode of 27.4 days per sector, TESS is most sensitive to planets with an orbital period shorter than 13 days. TESS will discover various types of exoplanets: worlds that look like Neptune, giant Jupiter-like planets, hot Jupiters (Jupiter-like planet with a very short orbit), Super-Earths (planets with masses between that of Earth and Neptune) and planets the size of Earth.

Recent Results

Following TESS’s first data release, eight new exoplanets have been confirmed and 443 candidates have been identified. These new worlds discovered by TESS are all very different from one another. New Neptune-like planets have been identified around stars HD 21749 and HD 219666. One of them (HD 21749 b) is a hot Neptune with an orbital period of only six days. Jupiter-like planets have also been found around stars HATS-71 and HD 202772. Two new hot Earths, Earth-like planet with an orbital period of about half a day, were also discovered.

Three of the exoplanets discovered in TESS’s first data release. (Credit: NASA/MIT/TESS)

One very interesting world is π Mensae c. It is a Super-Earth, with a period of only 6.27 days. Another planet, π Mensae b, was previously discovered in this system. π Mensae b is a giant planet with an orbital period of 2049 days. However, it is on an eccentric orbit, which challenges the formation process that leads to the existence of the planet c on a short orbit.

What’s next?

The new exoplanets discovered by TESS as well as the new candidates that will surely be confirmed shortly are very timely. TESS should be able to discover 500 new world orbiting M dwarf stars. These new exoplanets will be incredible targets for SPIRou (SPectropolarimètre InfraROUge), which will be very useful to measure their masses. TESS should also bring to light a handful of new Earth-like planets in the habitable zone of their stars. These new worlds will be excellent targets for the James Webb Space Telescope to study their atmospheres using transit spectroscopy.