NASA's newest planet hunter, the Exoplanet Transit Satellite ( TESS ), opened three new worlds – one slightly larger from Earth and two of the types not found in our solar system – orbiting a star nearby. The planets are bridging the gap in size of known planets and promise to be among the most curious targets for future exploration.
The object of interest of TESS (TOI) 270 is a pale, cool star, more commonly identified by its catalog name: UCAC4 191-004642. The M-type dwarf star is about 40% smaller than the Sun in size and mass and has a surface temperature about one-third cooler than the Sun. The planetary system is located about 73 light-years away in the southern constellation of Pictor.
"This system is exactly what TESS is designed to find – small, moderate planets that pass or pass inactive to the host star, one missing excessive stellar activity, such as flames," says lead researcher Maximilian Gunter, Ph.D. by Torres at the Massachusetts Institute of Technology ( MIT ) at the Institute of Astrophysics and Space Research in Cambridge, Cambridge. "This star is quiet and very close to us and therefore much brighter than the stars that host comparable systems. With extended follow-up observations, we will soon be able to determine the composition of these worlds, determine if the atmosphere is present and what gases they contain and others. ”
A document describing the system was published in the journal Nature Astronomy and is now available online.
The innermost planet, TOI 270 b, is probably a rocky world about 25% larger than Earth, it orbits the star every 3.4 days at a distance of about 13 times as close as Mercury to orbit the Sun. . Based on statistical studies of known exoplanets of a similar size, the scientific team estimates that TOI 270b has a mass about 1.9 times larger than Earth's.
Because of its proximity to the star, planet b is hot in a furnace world. Its equilibrium temperature – that is, the temperature based solely on the energy it receives from the star, which ignores the additional effects of warming from a possible atmosphere – is about 490 degrees Fahrenheit (254 degrees Celsius).
The other two planets, TOI 270 c and d, respectively, are 2.4 and 2.1 times larger than Earth and orbit the star every 5.7 and 11.4 days, respectively. Although only half their size, both may be similar to Neptune in our solar system, with the composition being dominated by gases rather than rocks and probably weighing about 7 and 5 times the earth's mass, respectively.
All planets are expected to rotate well to the star, which means that they rotate only once in each orbit and maintain the same side to the star at all times, just as the moon does in its orbit around Earth.
Planets c and d can best be described. like mini-Neptuni, a kind of planet that is not observed in our own solar system. Researchers hope that a further study of TOI 270 may help explain how two of these mini-Neptunians have formed around a nearly Earth-sized world.
"An interesting aspect of this system is that its planets are bridging a well-established gulf of known planetary size," said co-author Fran Pozuellos, a doctoral student at the University of Liège in Belgium, it is rare for planets to have sizes between 1.5 and twice the size of Earth for reasons related to the way planets are formed, but this is still a very controversial topic. TOI 270 is an excellent laboratory for studying the boundaries of this precipice and will help us better understand how planetary systems form and evolve. "
Gunter's team is particularly interested in the farthest planet, TOI 270 d. The team estimates the planet's equilibrium temperature to be about 150 degrees Fahrenheit (66 degrees C). This makes it the most moderate world in the system – and as such is a rarity among known transit planets.
"The TOI 270 is perfectly positioned in the sky to study the atmospheres of its outer planets with future NASA Space Telescope James NASA," said co-author Adina Feinstein, a doctoral student at the University of Chicago. "The Web will be monitored for more than half a year, which may allow for really interesting studies comparing the atmospheres of TOI 270c and d."
The team hopes that further research may reveal additional planets beyond the three known so far. If planet d has a rocky core covered by a dense atmosphere, its surface would be too warm for the presence of liquid water, considered a key requirement for a potentially habitable world. But subsequent studies may find additional rocky planets at slightly greater distances than the star, where cooler temperatures may allow liquid water to pool on their surfaces.
TESS is a NASA Astrophysics Explorer mission, managed and operated by MIT in Cambridge, Massachusetts and operated by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, headquartered in Falls Church, Virginia; Ames Research Center at NASA in California's Silicon Valley; The Harvard-Smithsonian Center for Astrophysics at Cambridge, Massachusetts; MIT Lincoln Laboratory; and the Baltimore Space Telescope Science Institute. More than a dozen universities, research institutes and observatories around the world are participating in the mission.