Two teams of astronomers have discovered an exoplanet almost identical in size to Earth just 40 light years away. It is one of the worlds most similar to our planet found so far and can be studied in great detail with current telescopes, say its discoverers.
“This planet is just around the corner on astronomical scales and has a very promising position with respect to its star to be able to host life,” he explains to this newspaper. Maria Rosa Zapateroresearcher at the Madrid Astrobiology Center (CAB) and co-author of one of the two studies that describe the new exoplanet, called Gliese 12 b.
Last fall, NASA’s TESS space telescope, which tracks brightness changes in tens of thousands of stars, captured an eclipse in Gliese 12, a star about three times smaller than the Sun in the constellation Pisces.
The observation set off alarm bells. The decrease in light captured could be due to the fact that there was a small planet passing just in front of the star. One day after NASA made the data public, a Spanish-Japanese team began analyzing the star with the Muscat 2 instruments, on Teide (Canary Islands), and Muscat 3, in Hawaii (United States). The Carmenes, in the Sierra de Filabres, Almería, and the IRD in Hawaii also pointed there, devices specialized in capturing the gravitational movement that a planet causes in its star when orbiting it and thus calculating its mass.
The results reveal the existence of a world with a radius almost equal to that of our planet, 90%, and a similar mass. On Gliese 12 b, a year lasts just under 13 Earth days, which is how long it takes the planet to complete one orbit.
Gliese 12 b is only 7% of the distance between the Sun and Earth, but since its star is fainter, it places it in the so-called habitable zone, where liquid water can exist on the surface, an essential condition for existence. of life. Astronomers estimate that the temperature on the planet’s surface may be between 10 and 41 degrees Celsius.
“The only thing we know about its composition is that it is probably rocky,” explains CAB astrophysicist José Caballero, co-author of the study. “It could be an ocean world, but we think it will be more like Earth or Venus. The most plausible thing is that it is almost completely rocky, with a thin atmosphere of nitrogen and water vapor and little liquid water on the surface. A habitable world, but hot and arid,” he highlights.
The complete results, signed by more than a hundred scientists from Spain, Japan, the United States and other countries, were published this Thursday in the specialized journal Astrophysical Journal Letters. A second team of British and Australian astronomers also publishes a second study on the same planet in the journal of the Royal British Astronomical Society.
Since 1995, 5,630 exoplanets have been discovered, but among all of them, Gliese 12 b would be among the four most similar to Earth, according to the study. The other three are around Trappist 1, another red dwarf that hosts a solar system with seven planets and is also about 40 light years away. Gliese 12 b appears to be alone around its star, possibly because the rest of the planets were expelled from the system or merged with each other.
The relative closeness of these worlds makes them priority targets for NASA’s James Webb Space Telescope, the most precise of its kind, which in the coming months will be able to confirm whether Gliese 12 b has an atmosphere. If so, in a year or two you could observe the light filtering through it and determine if it contains oxygen, water vapor, or carbon dioxide, signs that life may exist.
Red dwarf stars are the most abundant stars in our galaxy—73% of the total—much more abundant than yellow dwarfs like the Sun. Gliese 12 class stars have an ideal size and mass to find planets the size of the Earth in its surroundings. A smaller star means that eclipses are more pronounced with each transit, and a lower mass means that an orbiting planet produces a greater gravitational wobble in its star.
Red dwarfs are less warm than the Sun, which makes their habitable zones closer, or in other words, they complete their years in just Earth days, which makes the discovery of planets on scales much more viable. reasonable time. To find a twin of the Earth in a star like the Sun, you would have to wait at least 365 days to capture a single eclipse.
Red dwarfs tend to be magnetically active, emitting X-ray emanations that would be quite lethal to anything alive on a planet’s surface. It is one of the problems that the three habitable planets of Trappist-1 may have. However, analyzes by both teams conclude that Gliese 12 shows no signs of such violent behavior.
The discovery of this new planet once again puts humanity in an uncomfortable place, as astrophysicist María Rosa Zapatero explains. “I have no doubt that there is life in the universe beyond the solar system. Life may be bustling in Gliese 12 b. The problem is that it cannot be determined unambiguously that it exists, because this star is at a distance unreachable by any human ship. The most we can do from Earth is study its atmosphere. And for now we need more data,” she warns.
Francisco J. Pozuelos, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC), offers an independent opinion on this finding: “It is a new candidate among small and temperate planets and also seems optimal for studying its atmosphere well,” he acknowledges. The scientist adds that the mass of the new planet “is not well defined” and that more observations will be necessary to refine it. “Without a doubt this new planet is going to be observed with James Webb, although being alone may not provide as much knowledge. One of the good things about knowing a solar system with seven planets like Trappist-1 is that we can do comparative planetology and understand how they formed,” he adds.
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