An article published in “The Astrophysical Journal Letters” reports the discovery of a gaseous exoplanet in the DS Tuc binary system thanks to the use of NASA’s TESS space telescope. A team of astronomers coordinated by Dartmouth College, New Hampshire, USA, conducted this research on the exoplanet named DS Tuc Ab, which has an estimated age of about 45 million years, a sort of preteen. It has completed its growth but it’s still in a phase in which changes take place, all useful information to understand the formation and evolution of the planets.
About 150 light years from Earth, the DS Tuc system, also known with other catalogue names such as HD 222259 and TIC 410214986, is part of a stellar association, a set of stars with weaker gravitational bonds than star clusters, called Tucana-Horologium. It’s a binary system in which the star DS Tuc B is an orange dwarf with a mass that is about three quarters of the Sun’s while DS Tuc A is similar to the Sun but with about a hundredth of its age.
The DS Tuc system is well known as it’s relatively close from an astronomical point of view and for this reason when the TESS space telescope, launched on April 18, 2018, identified an exoplanet candidate at the time cataloged as TOI (TESS Objects of Interest) 200.01 which orbits DS Tuc A, raised the interest of a team of astronomers led by Elisabeth Newton of Dartmouth College.
The existence of the exoplanet was confirmed using data from NASA’s Spitzer space telescope and ground-based telescopes such as the South African Large Telescope (SALT) and was then named DS Tuc Ab. Its size was estimated around 5.70 times the Earth’s, about half of Jupiter’s, between Neptune’s and Saturn’s. Unlike the solar system’s gas giants, it’s very close to its main star, so its year lasts just over 8 Earth days.
The young exoplanet DS Tuc Ab completed its growth but is still going through a phase of changes. It’s contracting due to internal cooling but due to its proximity to its main star the stellar wind is slowly taking away its atmosphere.
The exoplanet DS Tuc Ab was discovered using the transit method, which means exploiting its passages between its main star and the Earth. This will make it possible to carry out more follow-up studies and Elisabeth Newton’s team intends to continue the one already started, trying for example to estimate the planet’s mass and examining its atmosphere, also to understand its composition.
The evaporation of the exoplanet DS Tuc Ab’s atmosphere will be one of the objectives of future research, to better understand the evolution processes of planets of that type. According to one of the models developed over the last few years, hot Neptunes, gaseous exoplanets with size similar to Neptune’s or smaller and very close to their star, could lose almost their entire atmosphere and eventually become super-Earths. DS Tuc Ab is bigger than Neptune and maybe it’s massive enough to keep part of its huge gaseous envelope, a future that will have to be investigated.
