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| This illustration shows one interpretation of what GJ 357 d may be like. |
A potentially habitable 'super-Earth' has been discovered just 31 light-years away from our solar system, astronomers announced Wednesday.
The planet, named GJ 357 d, is about six times larger than Earth and orbits a dwarf sun GJ 357, much smaller than our own, every 55.7 days. The international team of astronomers that discovered the planet said in a news release that it could "provide Earth-like conditions."
“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 telescopes that will soon be online,” Lisa Kaltenegger, the director of the Carl Sagan Institute at Cornell and associate professor in astronomy, said in a statement. “If GJ 357 d were to show signs of life, it would be at the top of everyone’s travel list – and we could answer a 1,000-year-old question on whether we are alone in the cosmos.”
Without an atmosphere, the planet would have an equilibrium temperature of 64 degrees below zero, according to NASA, which would make it "more glacial than habitable."
While using NASA’s planet-hunting Transiting Exoplanet Survey Satellite (TESS) in early 2019, Kaltenegger's team first discovered another planet GJ 357 b, a “hot Earth," orbiting the dwarf sun.
The satellite finds other worlds by monitoring the nearest and brightest stars for periodic dips in light. These dips, called transits, suggest a planet may be passing in front of its star.
Follow up observations from the ground lead to the discovery of two more planets orbiting the dwarf sun, including the super-Earth. Two of the planets discovered are considered too hot to support life as we know it, but GJ 357 d is in the host star's habitable zone meaning it's not too hot or too cold.
Kaltenegger told NBC News that a pair of telescopes that are expected to begin operating in 2021 and 2025 should reveal whether the planet is rocky or has oceans.
“This is definitely going to be one of the best targets for these telescopes because it’s so close and so bright,” Kaltenegger told NBC News. “This means we can collect that light and analyze it further to see the chemical composition of the atmosphere, or if we see signs of liquid water or oxygen. The closer the better and the brighter the better, and this one happens to be both.”
