Red dwarf stars, or M dwarf stars, are the most common type of star in the Universe. Recent research into an Earth-like planet orbiting such a star has revealed that it has no atmosphere. According to the researchers behind the study, this discovery could bring about a major shift in the way we search for extraterrestrial life.
Because these stars are so common, the discovery of GJ 1252b – the planet in question – with no atmosphere could mean that a large number of planets orbiting such stars could probably not host 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 extremely hot and quite inhospitable.
“The star’s radiation pressure is immense, enough to blow away a planet’s atmosphere,” said Michelle Hill, an astrophysicist at UC Riverside and co-author of the study, published in The Astrophysical Journal Letters, in a press release.
How planets are losing their atmosphere
The earth also loses part of its atmosphere over time due to the intense radiation from the sun. But on our planet, a combination of volcanic emissions and other carbon cycle processes are replenishing what is mostly being lost. But for a planet like GJ 1252b, which has a much closer orbit with its star, it’s almost impossible to replenish the lost atmosphere.
This is exactly what happens with Mercury in our solar system. The planet closest to the sun technically has an atmosphere, but it’s an extremely thin one, made up of atoms that solar radiation has blasted off its surface. The extreme heat on Mercury causes most of these atoms to escape into space.
How do scientists know GJ 1252b has no atmosphere?
A secondary solar eclipse occurs when a planet passes behind a star, blocking the planet’s light and the light reflected from its star. Astronomers have measured infrared emissions from GJ 1252b as it was obscured by one such eclipse.
This infrared radiation showed that the planet’s temperatures are scorching during the day, tipping the scales at about 1227 degrees Celsius. That’s hot enough to melt all the gold, silver, and copper on the planet. Because of this heat and the low surface pressure on the planet, scientists concluded that there is no atmosphere there.
“The planet could have 700 times more carbon than Earth and it still wouldn’t have an atmosphere. It would build up at first, but then subside and erode,” Stephen Kane, UCR astrophysicist and co-author of the study, said in a press statement.
The chances of a habitable planet
All of the above factors, combined with the fact that M dwarfs tend to exhibit more flare and activity than the Sun, mean that it is extremely unlikely that planets closely surrounding such planets will be able to hold their atmospheres.
But Earth’s solar neighborhood has about 5,000 stars, and most of them are M dwarf stars. But even excluding M dwarfs, there are still about 1,000 Sun-like stars that could harbor 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 rocky planets around these stars will become Mercury’s destiny. I remain optimistic,” added Hill.