Scientists using a NASA space telescope have discovered a tantalizing world. It’s about the size of Earth, is remarkably close to our solar system, and could be comfortable for life as we know it.
The extrasolar planet, or ‘exoplanet’, called Gliese 12 b, orbits a small and cool red dwarf star located only about 40 light-years from Earth in the constellation Pisces. The exoplanet – which the team discovered with NASA’s Transiting Exoplanet Survey Satellite (TESS) – is estimated to have a width of about 1.1 times that of Earth, making it similar to both our planet and Venus, which often occupies our solar system. world is mentioned. twin.”
Gliese 12 b orbits so close to its star, Gliese 12, that its year is only 12.8 Earth days. However, because the red dwarf Gliese 12 is only about a quarter the size of the Sun, it is also much cooler than our star. This means that even though Gliese 12 b is at a distance from its red dwarf parent equivalent to only 7% of the distance between the Sun and Earth, it is still in the habitable zone of its planetary system. The habitable zone, also known as the ‘Goldilocks Zone’, is the area around a star that is neither too hot nor too cold for planets to host liquid water, an essential ingredient for life as we know it. But more importantly, the two teams behind the discovery of Gliese 12 b cannot yet say with certainty whether an atmosphere is present. It therefore remains unclear whether the world could be habitable, but researchers have some cautious optimism.
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“The most important thing is that this is a planet that is very close; in fact, it is one of the closest planets to Earth,” said scientist Larissa Palethorpe of the University College of London, who, together with astrophysicist Shishir of the University or Southern Queensland led the investigation. Dholakia, told Space.com. “It’s in the habitable zone of its star or right on the edge of it – so it could be habitable.”
If Earth and Venus had a child
Scientists spotted Gliese 12 b as it crossed the face of its red dwarf star. These transits cause small dips in the light that TESS can clearly detect. Palethorpe added that when the team started this project, they weren’t sure what the orbital period or the size of the planet would be.
“It was a nice surprise to find out it was the size of Earth,” she continued. “So that was really fun to capture, but I think especially knowing that it could be, in terms of habitability, between Earth and Venus is really exciting.”
Gliese 12 b receives about 85% of the radiation that Venus gets from the Sun, but it is believed to have a much cooler surface temperature of 107 degrees Fahrenheit (42 degrees Celsius) compared to Venus’s surface temperature of 867 degrees Fahrenheit (464 degrees Celsius). ).
Although Earth and Venus are both in the sun’s habitable zone, one can support life and have a favorable atmosphere, while the other is an inhospitable hellscape with temperatures high enough to melt lead. Studying Gliese 12 b could help us understand why this is the case.
“Gliese 12 b could teach us a lot about how our own solar system evolved as well,” Palethorpe added.
The team will now investigate whether Gliese has an atmosphere, but early indications are that if it does, that atmosphere would be relatively thin. But perhaps surprisingly, the lack of a thick atmosphere is good news for the planet’s habitability prospects.
“We know that some planets have a very thick atmosphere of hydrogen covering the entire planet. This very thick layer of gas is actually bad news for habitability,” Palethorpe’s fellow UCL researcher Vincent Van Eylen told Space. com. ‘These planets are usually two or three times the size of Earth. Gliese 12 b is the actual size of Earth, so it probably doesn’t have a very thick atmosphere.
“It could either have no atmosphere, which wouldn’t be good for habitability, or it could have a kind of thin atmosphere, a bit like Earth’s.”
But even if Gliese 12 b has no atmosphere, it could still be an important test subject for furthering our search for life elsewhere in the Milky Way. That’s because the star it orbits, as a red dwarf, is the most common form of star in our Milky Way — yet one we know relatively little about when it comes to red dwarf planetary systems.
Living around red dwarfs
In the Milky Way, red dwarfs are the largest family of stars that still fuse hydrogen to helium in their cores, a process that defines a star’s so-called “main sequence” lifetime. It is estimated that 60% to 70% of the stars in our Milky Way are red dwarfs, such as Gliese 12, and of the 30 stars closest to Earth, at least 20 are red dwarfs.
“It is interesting to learn more about the planets around the small stars, what they might look like and whether life could exist on such planets,” Van Eylen added.
Officially known as K-type or M-type stars, red dwarfs have between 7.5% and 50% of the mass of the Sun. This low mass, relative to the Sun, means that such stars burn at a lower temperature, reaching only 6,380 degrees Fahrenheit (3,500 degrees Celsius) compared to our star’s 9,900 degrees Fahrenheit (5,500 degrees Celsius) temperature. Gliese 12, for example, has a surface temperature about 60% that of the Sun.
This lower temperature means that dimly shining red dwarfs can exist as main sequence stars for much longer than moderately massive stars like the Sun. Although the Sun is expected to live for about 10 billion years, red dwarfs are predicted to live dozens or even hundreds of times during this period. Sometimes that figure can extend to trillions of years. What this means is that life would have more time to develop on planets orbiting red dwarfs than on planets orbiting larger main sequence stars.
But it’s not all good news for the prospects of life on exoplanets orbiting the red dwarf.
Although cooler than the Sun in their maturity, red dwarfs are thought to be much wilder than our star. This class of stars is believed to be very magnetically active, emitting frequent and powerful bursts of high-energy light in the form of X-rays. These X-rays can violently strip the atmosphere of a planet close to a red dwarf.
Moreover, recent research has suggested that even red dwarfs that remain calm for many years can suddenly erupt with superflares that are 100 to 1,000 times more powerful than the Sun’s solar flares. These eruptions are more common in the youth of this star class and are also capable of stripping atmospheres and boiling away liquid water, even in habitable zones.
At the moment, however, both teams involved in the discovery of Gliese 12 b think the red dwarf is relatively quiet in orbit, which could be good news for the chances of the exoplanet possessing an atmosphere.
Red dwarf exoplanets are good TESS targets
The fact that red dwarfs are cooler than stars like the Sun and therefore that their habitable zones are closer to the stars makes detecting exoplanets around them a little easier for TESS and its transit method of searching for planets.
“We have a preference for detecting planets that are close to their host stars just because they pass more often. If we find planets orbiting red dwarfs because they are smaller stars, the transit obscuration is greater,” Palethorpe said . ‘Because red dwarfs are slightly cooler, the habitable zone is closer to the star than would be the case with our kind of sun, meaning we are more likely to detect planets in the habitable zone with TESS.’
The team will have to use instruments other than TESS to further investigate this planet. They will also turn to a different method of exoplanet detection to better define the characteristics of Gliese 12 b. One is called the “radial velocity method,” which uses the small wobbles that planets cause in the motion of their stars as they gravitationally pull on those stars.
“I think the next step is to determine the mass of the planet. We are already actively doing that as part of the High Accuracy Radial Velocity Planet Searcher for the Northern Hemisphere (Harps North) team,” says Palethorpe. said. “Then we also have another proposal accepted at the European Organization for Astronomical Research in the Southern Hemisphere (ESPRESSO), another radial velocity telescope. And so we will hopefully do this based on sort of radial velocity observations.”
Palethorpe and Van Eylen also hope to get time with the James Webb Space Telescope (JWST) to further investigate the planet’s atmosphere. This is possible because as Gliese 12 b moves through the plane of its star, the light passing through its atmosphere will bear the characteristic fingerprints of elements in the atmosphere.
This process is called “transmission spectroscopy,” and Gliese 12 b is just one of a handful of temperate, Earth-like worlds close enough to be examined in this way.
The JWST is currently conducting a similar survey of the seven Earth-like planets of the TRAPPIST-1 system, which are located approximately 40 light-years away. These planets are similar to Gliese 12 b in that not only are they in their star’s habitable zone, but the star is also a small, cool red dwarf.
“I think with the JWST we’ll at least get some clues about the atmosphere of this planet, which I think would be the most exciting thing to do now that it’s been discovered,” Van Eylen said.
When it comes to the possibility that Gliese 12 b will harbor life, the two scientists are extremely cautious. After all, it’s early days both for our understanding of this world and for methods that would be able to detect signs of life in an exoplanet atmosphere, even one as relatively close as Gliese 12 b.
“I think Gliese 12 b will teach us a lot about life, but we can’t say anything for sure. I think it’s very exciting and we should definitely look forward to more research on Gliese 12 b,” Palethorpe concluded. “It’s not a bad place to hunt for life.”
The two teams’ research was published Thursday (May 23) in The Monthly Notices of the Royal Astronomical Society and The Astrophysical Journal Letters.
Originally published on Space.com.