Scientists have discovered a theoretically habitable planet the size of Earth | CNN

R. Hurt/JPL-Caltech/NASA

Gliese 12b orbits a cool red dwarf star just 40 light-years away.

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Two teams of scientists have discovered a theoretically habitable planet, smaller than Earth but larger than Venus, orbiting a small star about 40 light-years away.

The exoplanet, called Gliese 12b, orbits a cool red dwarf star in the constellation Pisces and is about 27% the size of our Sun and 60% the temperature, according to the two studies published Thursday in The Astrophysical Journal Letters and Monthly. Announcements from the Royal Astronomical Society.

Because its star is so much smaller than the Sun, Gliese 12b is still within the habitable zone – the ideal distance from a star where liquid water can exist – even though it completes its orbit every 12.8 days.

Based on the assumption that the exoplanet has no atmosphere, scientists calculated that the surface temperature would be about 107 degrees Fahrenheit (42 degrees Celsius).

“We have found the closest transiting temperate world the size of Earth yet,” said Masayuki Kuzuhara, project assistant professor at the Astrobiology Center in Tokyo and co-leader of one of the research teams with Akihiko Fukui, a researcher. project assistant professor at the University of Tokyo, in a statement.

Once temperate Earth-sized planets are identified, scientists can analyze them to determine what elements are in their atmospheres and, crucially, whether water is present to sustain life.

“There are only a handful of exoplanets we’ve found that are good candidates for that. And this is our closest one and so that’s a pretty big discovery,” Larissa Palethorpe, a PhD candidate at the University of Edinburgh and University College London who co-led the other study, told CNN on Friday.

Understanding Gliese 12b

To discover Gliese 12b, scientists used the publicly available data collected by NASA’s Transiting Exoplanet Survey Satellite (TESS) – a telescope that stares at tens of thousands of stars every month and tracks their changes in brightness, which could provide evidence of the existence of exoplanets in orbit.

It is easier for astronomers to find exoplanets orbiting red dwarf stars because their relatively small size results in a greater dimming effect during each transit.

At this point, scientists don’t know exactly what this planet’s atmosphere is, whether it has one at all, and whether water is present, although Palethorpe said they don’t expect to find water there.

“There could be no water, and then we know that this planet has already had a runaway greenhouse effect and it’s more like Venus,” she said. “There could be water, in which case it’s more like us… or there are signatures that are detectable that could show you that the runaway greenhouse effect is going on, so it could be losing water.”

For the next stage of analyzing the exoplanet’s atmosphere, scientists hope to use the James Webb Space Telescope and conduct spectroscopy analyses. This method involves capturing starlight shining through an exoplanet’s atmosphere and seeing which wavelengths are absorbed by certain molecules, revealing their presence in the atmosphere.

In addition to shedding light on the exoplanet itself, Palethorpe said scientists hope this work can help us better understand our own planet.

“What this planet in particular will teach us is what happened when Earth remained habitable, but what Venus did not. It can tell us what habitability paths planets follow as they evolve,” she said.

But while the exoplanet could potentially be habitable for humans and is relatively ‘close’ to our solar system in astronomical terms, it’s unlikely anyone will visit anytime soon.

“It’s not reachable, it’s 12 parsecs away,” Palethorpe said, adding that it would take about 225,000 years to reach Gliese 12b with the fastest spacecraft currently in existence.

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