The most prevalent type of star in the universe, the M dwarf, has an Earth-like planet orbiting it that appears to have no atmosphere at all. This discovery could cause a major shift in the search for life on other planets.
This discovery implies that a large number of planets orbiting these stars may also lack atmospheres and, as a result, are unlikely to support life because M-dwarfs are so common.
The Astrophysical Journal Letters provides a detailed account of the research that produced the discoveries regarding the GJ 1252b no-atmosphere planet.
In a day on Earth, this planet makes two orbits around its star. In addition to being inhospitable, GJ 1252b is significantly larger than Earth and is located much closer to its star than Earth is to the sun.
"The pressure from the star's radiation is immense, enough to blow a planet's atmosphere away," said Michelle Hill, UC Riverside astrophysicist, and study co-author.
The sun also causes Earth to lose some of its atmosphere over time, but volcanic emissions and other carbon-cycling processes help to replenish what is lost, making the loss hardly noticeable. However, a planet cannot continue to replenish the amount lost when it is closer to a star.
This is how Mercury is disposed of in our solar system. It does have an atmosphere, but it is very thin and is composed of atoms that the sun has blasted off its surface. These atoms escape into space due to the planet's intense heat.
Astronomers observed GJ 1252b during a secondary eclipse and measured the planet's infrared radiation to determine that it is devoid of an atmosphere. This kind of eclipse happens when a planet passes in front of a star, blocking both the light from the planet and the light reflected from the star.
The radiation revealed the planet's sweltering daytime temperatures, which are thought to reach 2,242 degrees Fahrenheit. This temperature is so high that it would melt gold, silver, and copper on the surface of the planet. The researchers believed there is no atmosphere because of the heat and the alleged low surface pressure.
Even with a tremendous amount of carbon dioxide, which traps heat, the researchers concluded GJ 1252b would still not be able to hold on to an atmosphere.
"The planet could have 700 times more carbon than Earth has, and it still wouldn't have an atmosphere. It would build up initially, but then taper off and erode away," said Stephen Kane, UCR astrophysicist and study co-author.
M dwarf stars tend to have more flares and activity than the sun, further reducing the likelihood that planets closely surrounding them could hold on to their atmospheres.
"It's possible this planet's condition could be a bad sign for planets even further away from this type of star," Hill said. "This is something we'll learn from the James Webb Space Telescope, which will be looking at planets like these."
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