Scientists using the NASA space telescope have discovered an exciting world. It is about the size of Earth, very close to our solar system, and could be suitable for life as we know it.
The extrasolar planet, or “exoplanet,” called Gliese 12 b, orbits a small, cool red dwarf star about 40 light-years from Earth in the constellation Pisces. The exoplanet the team found with NASA’s Transiting Exoplanet Survey Satellite (TESS) is estimated to be about 1.1 times as wide as Earth, making it similar to our planet and Venus, which is often referred to as our Earth’s solar system. twins.”
Gliese 12 b orbits so close to its star Gliese 12 that its year lasts only 12.8 Earth days. But since the red dwarf Gliese 12 is one-quarter the size of the Sun, it is much cooler than our star. This means that although Gliese 12 b is only 7% of the distance from its red dwarf parent equivalent to the distance between the sun and Earth, it is still in the planetary system’s habitable zone. The habitable zone, also known as the “Goldilocks Zone,” is the region around a star that is neither too hot nor too cold for planets to host liquid water, a vital ingredient for life as we know it. But more importantly, the two teams behind the discovery of Gliese 12 b are not yet sure whether it has an atmosphere. Therefore, it remains unclear whether the world will be habitable, but researchers are cautiously optimistic.
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“The most interesting thing is that this is a really close planet; in fact, it’s one of the closest passing planets to Earth,” said University College of London scientist Larissa Palethorpe, who led the research with University of Southern Queensland astrophysicist Shishir. Dholakia told Space.com. “It’s either in the habitable zone of its star or right at its edge, so it could be habitable.”
If Earth and Venus had children
Scientists detected Gliese 12 b as it passed, or “transited,” the face of its parent red dwarf star. These transitions cause tiny dips in light that TESS is adept at detecting. Palethorpe added that when the team entered this project, they did not know for sure what the orbital period or the size of the planet would be.
“It was a very pleasant surprise to find that it was such a similar size to Earth,” he continued. “So being able to detect that was a really neat thing, but I think it’s really exciting to know that this could be located between Earth and Venus, especially from a habitability standpoint.”
Gliese 12 b receives about 85% of the radiation that Venus receives from the sun, but is thought to have a much cooler surface temperature of 107 degrees Fahrenheit (42 degrees Celsius) compared to Venus’ surface temperature of 867 degrees Fahrenheit (464 degrees Celsius). ).
Although Earth and Venus are in the sun’s habitable zone, one is capable of supporting life and has a conducive atmosphere, while the other is an inhospitable hellscape hot enough to melt lead. Examining Gliese 12b may help us understand why this is the case.
“Gliese 12b can also teach us a lot about how our own solar system developed,” Palethorpe added.
The team will now investigate whether Gliese has an atmosphere; but early indications suggest that the atmosphere, if present, would be relatively thin. But surprisingly, the lack of a thick atmosphere is good news for the planet’s habitability.
Palethorpe’s UCL researcher Vincent Van Eylen told Space.com: “We know that some planets have very thick hydrogen atmospheres that cover the entire planet. This very thick layer of gas is actually bad news for habitability.” “Usually these planets are two or three times the size of Earth. Gliese 12 b is the actual size of Earth, so it probably doesn’t have such a thick atmosphere.”
“It could either have an atmosphere that’s not very good for habitability, or it could have a thin atmosphere like Earth’s.”
Still, even if Gliese 12 b lacks an atmosphere, it could be an important test subject to advance our search for life elsewhere in the Milky Way. This is because the star it orbits, a red dwarf, is the most common form of star in our galaxy; But when it comes to red dwarf planet systems, we know relatively little about them.
Life around red dwarfs
In the Milky Way, red dwarfs constitute the largest family of stars that still convert hydrogen into helium in their cores; this is a process that defines the so-called “main sequence” lifetime of a star. It is estimated that 60% to 70% of the stars in our galaxy are red dwarfs, such as Gliese 12, and at least 20 of the 30 stars closest to Earth are red dwarfs.
“It’s interesting to know about planets around small stars, what they might look like and whether life could exist on such planets,” Van Eylen added.
Red dwarfs, formally known as K-type or M-type stars, have between 7.5% and 50% of the mass of the sun. This lower mass relative to the Sun means that such stars burn at a lower temperature; It reaches a temperature of only 6,380 degrees Fahrenheit (3,500 degrees Celsius), compared to our star’s 9,900 degrees Fahrenheit (5,500 degrees Celsius). For example, Gliese 12’s surface temperature is around 60% of that of the Sun.
This low temperature means that dimly shining red dwarfs can exist as main sequence stars for much longer than medium-sized stars like the Sun. Although the Sun is expected to live for about 10 billion years, red dwarfs are predicted to have a lifespan tens or even hundreds of times that time. Sometimes this figure can extend up to trillions of years. This means that life will have more time to develop on planets orbiting red dwarfs than on planets around larger main sequence stars.
But this is not good news for the possibility of life on exoplanets orbiting red dwarfs.
Red dwarfs are believed to be much wilder than our star, even though they are cooler than the sun in their stellar adulthood. This class of stars is believed to be extremely magnetically active, spewing out frequent and powerful bursts of high-energy light in the form of X-rays. These X-rays can violently strip the atmosphere of a near-red dwarf planet.
Additionally, recent research has suggested that even red dwarfs that remain quiescent for many years can suddenly explode with superflares 100 to 1000 times more powerful than the Sun’s solar flares. These explosions are more common in the young of this class of stars and are also capable of stripping the atmosphere and boiling away liquid water, even in habitable zones.
But both teams currently involved in the discovery of Gliese 12 b think the orbiting red dwarf is relatively quiet, which could be good news for the exoplanet’s chances of having an atmosphere.
Red dwarf exoplanets are good TESS targets
The fact that red dwarfs are cooler than stars like the Sun, and therefore their habitable zones are closer to the stars, actually makes it a little easier for TESS and its transit planet hunting method to detect exoplanets around them.
“We actually have biases towards detecting planets that are closer to their host stars because they transit more frequently. When we find planets orbiting red dwarfs because they are smaller stars, the dimming of the transit is greater,” Palethorpe said. “Because red dwarfs are slightly cooler, the habitable zone is closer to the star than our sun, meaning we are more likely to detect planets in the habitable zone with TESS.”
The team will need to use instruments other than TESS to further investigate this planet. They will also switch to a different exoplanet detection method to better define the properties of Gliese 12b. One of these is called the “radial velocity method”; This method takes advantage of small wobbles in the motion of stars caused by planets as they gravitationally pull on stars.
“I think the next step will be to determine the mass of the planet. We are already actively doing this as part of the High Accuracy Radial velocity Planet Seeker for the Northern Hemisphere (Harps North) team, which is a radial velocity telescope,” Palethorpe said. aforementioned. “Then we also have another proposal that has been accepted with the European Organization for Research in Astronomy in the Southern Hemisphere (ESPRESSO), which is another radial velocity telescope. And so, I’m hoping that we’ll do that from some sort of radial velocity observations.”
Palethorpe and Van Eylen also hope to be given time to further investigate the planet’s atmosphere with the James Webb Space Telescope (JWST). This is possible because as Gliese 12 b passes across the face of its star, the light passing through its atmosphere will carry characteristic fingerprints of the elements in the atmosphere.
This process is called “transmission spectroscopy,” and Gliese 12b is only one of a handful of temperate Earth-like worlds close enough to be studied this way.
JWST is currently conducting a similar survey of the seven Earth-like planets of the TRAPPIST-1 system, located about 40 light-years away. These planets are similar to Gliese 12 b because not only are many of them in the habitable zone of their stars, but this star is also a small, cool red dwarf.
“With JWST we will get at least some clues about the atmosphere of this planet, and I think that will be the most exciting thing to do now that it has been discovered,” Van Eylen said.
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The two scientists are extremely cautious when it comes to the possibility that Gliese 12b could host life. After all, it is still early days both for our understanding of this world and for methods that can detect signs of life in the atmosphere of a planet even as close as Gliese 12 b.
Palethorpe concluded: “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 further research on Gliese 12 b.” “Not a bad place to start life’s quest.”
The two teams’ research was published Thursday (May 23) in The Monthly Notices of the Royal Astronomical Society and The Astrophysical Journal Letters.