NASA has announced that the TESS (Transitioning Exoplanet Survey Satellite) mission has completed its first 12 months of surveying the skies. During its first year, TESS has discovered 21 planets outside of our solar system. TESS has also captured data on other interesting events in the southern sky.
TESS started hunting for exoplanets in the southern sky in July of 2018. It has also collected data on supernovae, black holes, and other phenomena in its line of sight. NASA says that along with the planets that TESS has discovered the mission has also identified over 850 candidate exoplanets that are waiting for confirmation using ground-based telescopes.
TESS principal investigator George Ricker says that the pace and productivity of TESS over its first year have far exceeded the most optimistic hopes of the scientists. TESS uses four large cameras to watch a swatch of the sky that measures 24-by-96-degree for 27 days at a time. Some of the sections overlap, so some parts of the sky were observed for nearly the entire year.
TESS concentrated on stars closer than 300 light-years from our solar system and watched for transits. A transit is a dip in the brightness of a star caused by an object, like a planet, passing in front of the star. The TESS survey of the southern sky was completed on July 18, and the spacecraft has now turned its cameras to the northern sky.
NASA says that when the spacecraft completes its survey of the northern sky in 2020, it will have mapped over 3/4 of the sky. The reason TESS is focusing on stars within 300 light-years is to allow followup with ground-based telescopes for further study. To qualify as an exoplanet, the object must make at least three transits in TESS data in addition to passing other checks to make sure the transits weren’t false positives caused by a companion star or eclipse.