NASA is celebrating the first year in orbit of the Transiting Exoplanet Survey Satellite (TESS). TESS took over from Kepler for the exoplanet hunt, especially for potential exoplanets within a radius of just 300 light-years around the Sun.
As of July 26, 2019, the Encyclopedia of Extrasolar Planets indicates that Humanity is aware of 4,122 exoplanets in the Milky Way. But many other observations collected in orbit or on Earth are known and are considered as serious candidates for exoplanet signing.
One of the satellites that Homo Sapiens put into orbit to explore its galactic territory in search of answers about its origins, especially if it was alone and if the biosphere had appeared in an exceptional way in the Galaxy, was called Kepler. Before ending in October 2018, Kepler had dramatically increased the number of exoplanets detected in the Milky Way.
Another of NASA’s satellites, even more powerful, also scrutinizes the arcana of the cosmos for the same purpose since July 2018. This is the Transiting Exoplanet Satellite Survey (TESS) which, as the name suggests, hunts exoplanets by the method of transits, a technique exploiting light curves by photometry. Clearly, TESS measures the variations in the luminous intensity of many stars on the celestial vault, looking for periodic falls of this intensity with characteristics that strongly suggest that we have witnessed at least three passages of an exoplanet in front of his star host.
The method generally only provides the radius and orbital period of the potentially detected exoplanet. This detection is confirmed and its mass is then determined by another method on the ground, that of the radial velocities. Knowing mass and radius, we can deduce a density, which allows identifying possible ocean planets.
TESS, however, has slightly different goals than Kepler. The key is to start looking for rocky exoplanets that lie within only 300 light-years from the sun. Twenty have been found and confirmed to date in the skies of the Southern Hemisphere, but astronomers already have about 850 candidates under investigation to join the list.
So far, the exoplanets discovered by TESS are often smaller than Neptune, but larger than the Earth. Their sizes are at least 80% larger than those of our Blue Planet to diameters comparable to or greater than those of Jupiter and Saturn.
TESS does not only provide targets for studies related to exobiology. The satellite can also discover new comets in the Solar System and beyond. The most spectacular example is probably the identification of exocomets around the famous Beta Pictoris star.