Super-Earth 31 light-years away discovered by astronomers. One of the closest worlds ever detected could harbour liquid water on its surface and may be habitable.
NASA’s Transiting Exoplanet Survey Satellite, or TESS, a super-powerful orbiting telescope scouting the sky for alien worlds, found a new planet in the Hydra constellation surrounding a neighbouring star. They found two more worlds orbiting it when astronomers checked the star for confirmation.
If it turns out to have a dense atmosphere and be made of rock, one of those planets, called GJ 357 d, could support liquid water. It is one of the 45 nearest exoplanets confirmed to date, out of a total of 4,025 planets outside of our solar system so far.
This planet system is the third closest recognized using the “transit” technique in which telescopes watch for small dips in the brightness of a star that a planet passing in front of it could cause. Although TESS has refined it, the Kepler telescope pioneered the method.
The promising planet is in the “habitable zone” of its star, the range of distances where the right surface temperature for liquid water could exist for the rocky world.
Diana Kossakowski, a member of the team that discovered the planet said: “GJ 357 d is located on the outer edge of the habitable zone of its star, where it receives about the same amount of stellar energy from its star as Mars from the Sun”.
“If the planet has a thick atmosphere, it could trap enough heat to warm the planet and enable liquid water on its surface,” said Kossakowski.
However, if the planet turns out to have no atmosphere, its surface would be well below the freezing point of water, about -64 degrees Fahrenheit (-53 degrees Celsius).
The mass of GJ 357 d is at least 6.1 times that of Earth, and every in 55.7 days the planet orbits its small star. However, without further study, scientists can’t tell much about it.
The most powerful planet-hunting telescope ever by NASA, TESS, watches thousands of stars for transits. Before moving on to a different patch, the telescope observes one part of the sky for 27 days at a period. As shown in the NASA graph below, it splits each half of the sky (the northern half and the southern half) into 13 patches. This month, the spacecraft finished the southern half of their journey and switched to the northern sky.
When the mission finishes next year around this time, over 85 per-cent of the sky will have been observed by TESS.
To date, more than 850 prospective new planets have been discovered by the telescope. The next step is for ground-based telescopes to examine the stars that these planets may be orbiting and identify whether the planets are exercising a gravitational pull.
Also Read: Dragonfly To Search For Life On Titan
That method is what allowed GJ 357 d to be found by scientists. They noticed gravitational pulls from two others as they worked to verify the planet that TESS spotted. (TESS did not see the two worlds because their orbits do not pass between their star and the telescope.)
So far, it has only confirmed 24 of the exoplanets that TESS has found. Astronomers verified the telescope detected three nearby planets earlier this week, including a “super-Earth,” although no one is assumed to have liquid water.
Scientists predict that before the mission ends, the telescope will identify thousands of exoplanet candidates. Some of those, including GJ 357 d, might be habitable.
Natalia Guerrero, who manages the MIT team identifying exoplanet candidates, said last week in a NASA press release that “The team is presently focused on identifying the best candidates to verify through ground-based follow-up.”
“But there are many more prospective exoplanet candidates still to be analyzed in the data, so we’re just seeing the tip of the iceberg here.”