The planet, dubbed GJ 357D, orbits a star approximately 31 light years distance from Earth. The super-Earth is in so-called habitable zone, an area far enough from its star to not be too hot but close enough to not be too cold. This “Goldilocks” region is possible for liquid water to exist on the surface of a planet if it is rocky, although further research is needed to confirm whether GJ 357D’s atmosphere is dense and warm enough to host liquid water.
The alien Earth news arrives only days after three new planets were discovered in a star system just 73 light years away from Earth — including two planets that may be ‘missing links’ in planetary formation.
Dr Diana Kossakowski, from the Max Planck Institute for Astronomy in Heidelberg, said: “GJ 357D is located within the outer edge of its star’s habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun.
“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.”
Professor Lisa Kaltenegger, of Cornell University, suggests the planet could harbour life.
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She said: “This is exciting, as this is humanity’s first nearby super-Earth that could harbour life – uncovered with help from Tess, our small, mighty mission with a huge reach.
“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.”
GJ 357D orbits its star every 55.7 days at a range of about 20 percent of Earth’s distance from the sun.
The three planets orbit a star known as GJ 357, an M-type dwarf, which is around 40 percent cooler than the Sun and about a third of its size.
NASA’s TESS is used to discover exoplanets beyond our solar system.
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TESS spotted the star dimming slightly every 3.9 days, suggesting planets were orbiting it.
The nearest of the three planets, GJ 357B, is around 22 percent larger than Earth, orbiting its star 11 times closer than Mercury does to the Sun.
Professor Enric Palle, an astrophysicist at the Institute of Astrophysics, said: “We describe GJ 357 b as a ‘hot Earth.
“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.”
The middle planet, GJ 357C, has a mass approximately 3.4 times Earth’s, and orbits around its star every 9.1 days.
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What is the TESS satellite?
NASA’s successor to the Kepler’s satellite is equipped with four cameras allowing it to view 85 percent of the entire sky, as it searches exoplanets orbiting stars less than 300 light-years away.
NASA hopes TESS will uncover new clues on the possibility of life elsewhere in the universe by studying brighter objects.
Its four wide-field cameras will view the sky in 26 segments, each of which it will observe one by one.
Paul Hertz, Astrophysics Division director at NASA’s Headquarters, said: “We learned from Kepler that there are more planets than stars in our sky, and now TESS will open our eyes to the variety of planets around some of the closest stars.
“TESS will cast a wider net than ever before for enigmatic worlds whose properties can be probed by NASA’s upcoming James Webb Space Telescope and other missions.”