M dwarf star,life aliens

Astronomers have made a discovery that could “dramatically narrow” the search for extraterrestrials

Red dwarf stars, or M dwarf stars, are the most common type of star in the universe. A recent study of an Earth-like planet orbiting such a star found it to have no atmosphere. According to the scientists behind the study, the discovery could cause a major shift in the way we search for extraterrestrial life.

Since these stars are so common, the discovery of GJ 1252b—the planet in question—without an atmosphere could mean that the large number of planets orbiting such stars would likely be unable to host any life. This Earth-like planet is slightly larger than ours and is much closer to its star than we are to our Sun. This makes GJ 1252b intensely hot and largely inhospitable.

“The star’s radiation pressure is enormous, enough to blow away the planet’s atmosphere,” Michelle Hill, a UC Riverside astrophysicist and co-author of the study published in The Astrophysical Journal Letters, said in a press statement.

How planets lose their atmospheres

Earth also loses some of its atmosphere over time due to intense radiation from the Sun. But on our planet, a combination of volcanic emissions and other carbon cycling processes replenish what is largely lost. But for a planet like GJ 1252b, which has a much closer orbit with its star, it is almost impossible to replenish the lost atmosphere.

This is exactly what is happening with Mercury in our solar system. The planet closest to the Sun technically has an atmosphere, but it’s extremely thin, made up of atoms blasted off its surface by sunlight. The extreme heat on Mercury means that most of these atoms escape into space.

How do scientists know that GJ 1252b has no atmosphere

A secondary eclipse is when a planet passes behind a star and blocks the light from the planet and the light that is reflected from its star. Astronomers measured infrared radiation from GJ 1252b when it was obscured by such an eclipse.

This infrared revealed that the planet’s temperatures are scorching during the day, tipping the scales at around 1,227 degrees Celsius. That’s hot enough to melt all the gold, silver and copper on the planet. Based on this heat and low surface pressure on the planet, scientists have concluded that there is no atmosphere.

“A planet could have 700 times more carbon than Earth and still have no atmosphere. It initially accumulates, but then narrows and erodes,” Stephen Kane, a UCR astrophysicist and co-author of the study, said in a press release.

A chance for a habitable planet

All of the above factors, combined with the fact that M dwarfs tend to have more flares and activity than the Sun, mean that it is extremely unlikely that planets closely surrounding such planets could retain their atmospheres.

But Earth’s solar neighborhood has about 5,000 stars, and most of them are M dwarf stars. But even if M dwarfs are excluded, there are still about 1,000 Sun-like stars that could host habitable planets. But M dwarf stars cannot be completely ruled out.

“If a planet is far enough away from an M dwarf, it could potentially retain an atmosphere. We cannot yet conclude that all the rocky planets around these stars are reduced to Mercury’s fate. I remain optimistic,” added Hill.

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