NASA's newest spacecraft has spied and confirmed a third world outside our solar system – only three months in the vehicle's scientific operations. This newly discovered planet, or exoplanet, is relatively close, orbiting a small star just 53 light-years away. And that means we may be able to study this world more extensively to find out what its atmosphere may contain.
The discoverer of these worlds is NASA's TESS satellite – a spacecraft the size of a refrigerator that was launched into orbit around the Earth in April. The vehicle is the successor to NASA's spacecraft, Kepler, which lies almost 100 million kilometers from Earth and has found thousands of distant exoplanets. Kepler ran out of fuel in October, shortly after the TESS mission began to come on stream. But the two spacecraft seek the sky in the same way: they look for small falls in the light of a distant star, whenever a planet crosses in front and momentarily blocks part of the star.
TESS, however, has a mission different from its ancestor. Kepler scoured an area of the sky all the time to find as many exoplanets as possible. These worlds were, however, incredibly distant, far distant to actually study and analyze further. But TESS is specifically looking for relatively close-Earth exoplanets. These worlds are then easier to see and study. We can analyze them with different telescopes, to determine their mass or what may be lurking in their atmospheres.
So with every new world that TESS meets, there is a chance to learn more about it in ways we could not do with other worlds we have discovered before. "The important thing about this especially unique system is close to us," said Diana Dragomir, postdoc at the Kavli Institute for Astrophysical and Space Research at MIT and head of the team who made the detailed breakthrough in O Astrophysical Newspaper Letters, account The Verge. "What that simply means is that we can study this system in detail. We can measure the mass of the planet and measure things about the star.
In September, NASA announced that TESS had found two candidate planets – two worlds that orbit around their stars in just a few hours and days. But this newly confirmed planet is a little more interesting. Like the first two discoveries, this third planet orbits a dwarf, a type of star that is smaller and weaker than our sun. But it orbits much further than the other two, taking 36 days to complete a journey around the star.
This makes it a much cooler planet than the other two, with an average temperature around 300 degrees Fahrenheit, "which is not so hot," says Dragomir. "It's a little warmer than the boiling point of the water." Astronomers have not been able to study planets in such cold temperatures before. But as the world is so close, it is possible for scientists to peer into their atmosphere and learn more about it in the future, possibly with NASA's upcoming James Webb Space Telescope due to be launched in 2021.
Dragomir and his team were also able to discover the mass of this planet by making follow-up observations with the Magellan Telescope in Chile. Although it is about three times the size of the Earth, it is 23 times more massive than our planet. This makes it a "sub-Neptune" in size, although it is much denser than Neptune. There is no hope that this world will be habitable, since it is more likely to be a gaseous planet and not rocky.
However, there may be other planet around the same star that this planet orbits around – one that is roughly the same size as Earth. The one, also discovered by TESS, has not yet been confirmed. But if it's out there, it would be a much warmer world, with a super close orbit that lasts only 7.8 days. And it would also be the first planet the size of Earth that TESS encountered. His discovery would mean that we could finally study an Earth-sized exoplanet more fully.
These are discoveries that make every new discovery of TESS so exciting for astronomers. "That's what TESS is designed to do: find these little planets around nearby stars, so now we can get their mass and get access to their atmospheres," says Dragomir.