TESS Object of Interest

A term used to identify objects observed and analysed by the Transiting Exoplanet Survey Satellite, or TESS. This satellite was launched in 2018, and continues to search the sky for exoplanets by monitoring for planets transiting across the faces of their parent stars. Its aims and approach are therefore somewhat similar to those of the Kepler mission, launched nine years earlier, but where Kepler watched for transits in a defined area of the northern sky, the orbit of TESS was designed so that it is able to search for exoplanets across the entire sky.

The design of the satellite's orbit divides the sky into ninety-two sectors, and TESS observes designated stars within each of these sectors for two full orbits of Earth (a period of a little over twenty-seven days) before moving on to the next. The initial mission was scheduled to last for two years, during which TESS scanned selected stars of brighter than magnitude +12, including those of the Sun-like G-type spectral class, as well as cooler K-type and M-type stars. The closest thousand red dwarfs to the Sun were also included in this initial survey, yielding a total of about half a million stars.

TESS announced its first confirmed exoplanet on 18 September 2018: a super Earth in a very close orbit around the star Pi Mensae (now also designated, as a TESS target star, TOI-144). Among numerous notable discoveries, TOI-700 d (identified in the year 2020) stands out as a relatively close analogue of Earth. One of the three known planets orbiting the red dwarf TOI-700 in Dorado, TOI-700 d has a similar size and mass to Earth, and orbits within its parent star's habitable zone.

The TESS project continues to operate, and has since confrmed a total of more than six hundred extrasolar planets, with thousands more still awaiting detailed analysis and possible verification.