After spending a year of monitoring in the southern sky, NASA’s Transiting Exoplanet Survey Satellite (TESS) has located a few interesting new exoplanets just 31 light-years from our home planet.
Several exoplanets – planets which orbit stars beyond our solar system – were found in the Hydra constellation orbiting around an M-dwarf star known as GJ 357. The star has a temperature around 40 percent colder than our sun, and it is roughly 33 percent of our sun’s mass and size.
GJ 357 b
The first of the three exoplanets that were found orbiting the star was GJ 357 b. The exoplanet is 22 percent bigger and has an 80 percent greater mass than Earth, which makes it a super-Earth. The exoplanet is 11 times nearer to GJ 357 than Mercury is to our sun, and it has an approximated average temperature of about 490 degrees Fahrenheit (254 degrees Celsius), not including the possible warming effects from the atmosphere – if there is one. It does a full orbit of its star in just under 4 days.
“We describe GJ 357 b as a ‘hot Earth,'” says Enric Pallé, co-author of the study and an astrophysicist at the Institute of Astrophysics of the Canary Islands. “Although it cannot host life, it is noteworthy as the third-nearest transiting exoplanet known to date and one of the best rocky planets we have for measuring the composition of any atmosphere it may possess.”
GJ 357 d
Another super-Earth, GJ 357 d, is situated in the outer perimeter of its star’s habitable region, where it experiences around the same quantity of stellar energy from GJ 357 as Mars gets from our sun. It has a mass just over 6 times more than Earth’s and it is at a distance where temperatures may be suitable for supporting liquid water on the surface. It has an average temperature of 64 degrees Fahrenheit (17.7 degrees Celsius) and it takes 55.7 days to orbit its star.
Co-author of the study at the Max Planck Institute for Astronomy, Diana Kossakowski, says, “If the planet has a dense atmosphere, which will take future studies to determine, it could trap enough heat to warm the planet and allow liquid water on its surface.”
“This is exciting, as this is humanity’s first nearby super-Earth that could harbor life – uncovered with help from TESS, our small, mighty mission with a huge reach,” said Lisa Kaltenegger, author of the study, associate professor of astronomy, and director of Cornell’s Carl Sagan Institute. “With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth and we could pick out signs of life with upcoming telescopes soon to be online.”