Planets around other stars need to prepare for extreme weather conditions, according to a new study from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, which examines the effects of X-rays on potential planets around the most common stars . Types of stars.
Astronomers have found that only planets like Earth that contain greenhouse gases in their atmospheres and are relatively far away from the stars they study have a chance of sustaining life as we know it around nearby stars.
Wolf 359 is a red dwarf star with about one-tenth the mass of the Sun. Red dwarfs are the most common stars in the universe, with lifespans of billions of years, providing plenty of time for life to develop. Wolf 359, which is only 7.8 light-years away, is also one of the closest stars to the solar system.
"Wolf 359 could help us unlock the secrets of stars and habitability," said Scott Wolk of the Center for Astrophysics, a Harvard and Smithsonian institution that led the research. "It's so close and it's in such an important class of stars - it's a great combination."
Because red dwarfs are the most common type of star, astronomers have a hard time finding exoplanets around them. Astronomers using optical telescopes have found some evidence of two planets orbiting Wolf 359, but these conclusions have been questioned by other scientists.
"While we don't yet have evidence that Wolf 359 has planets around it, it seems likely that it has multiple planets," Volker added. "This makes it a great testbed for observing what planets would experience around such stars."
Volker and his colleagues used Chandra and XMM to study the amount of stable X-rays and extreme ultraviolet (UV) radiation (the most energetic type of ultraviolet radiation) that Wolf 359 emits to possible planets around it.
They found that Wolf 359 is producing enough damaging radiation that only planets with greenhouse gases like carbon dioxide in their atmospheres and relatively far from their stars could possibly support life.
"Merely being far enough away from a star's harmful radiation is not enough to make it habitable," said co-author Vinay Kashyap of the CfA. "The planets surrounding Wolf 359 would also need to be covered in greenhouse gases like Earth."
To study the impact of high-energy radiation on the habitability of planet candidates, the team considered a star's habitable zone - the region around a star where liquid water could exist on a planet's surface.
The outer limit of Wolf 359's habitable zone is about 15% of the distance between Earth and the Sun, because the red dwarf is much less luminous than the Sun. Neither of the system's two candidate planets is in Wolf 359's habitable zone, with one too close to the star and the other too far away.
Co-author Ignazio Pillitteri from the CfA and the National Institute for Astrophysics said: "If the inner planet does exist, the X-ray and extreme ultraviolet radiation it would receive would be in the range of about a million Destroy the planet's atmosphere within a year." Palermo, Italy.
The team also considered the effects of radiation on as-yet-undiscovered planets in the habitable zone. They concluded that a planet like Earth in the middle of the habitable zone should be able to maintain an atmosphere for nearly two billion years, while a planet near the outer edge could do so indefinitely, aided by the warming effects of greenhouse gases Go down.
For planets orbiting stars like Wolf 359, another huge danger comes from X-ray flares, or occasional bursts of bright X-rays that appear in addition to the star's steady daily output. Combining observations from Chandra and XMM-Newton, 18 X-ray flares emitted by Wolf 359 were discovered over a 3.5-day period.
Extrapolating from these observed flares, the team expected more powerful and destructive flares to occur over longer periods of time. The combined effects of steady X-ray and ultraviolet radiation and flares mean that any planet in the habitable zone is unlikely to have an atmosphere long enough for multicellular life as we know it on Earth to form and survive. The outer edge of the habitable zone is an exception if the Earth has a significant greenhouse effect.
These results were presented at the 245thth meeting of the American Astronomical Society in National Harbor, Maryland, and is being prepared for publication in a journal. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations in Cambridge, Massachusetts, and flight operations in Burlington, Massachusetts.
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Megan Watzke
Chandra X-ray Center
Cambridge, Massachusetts
617-496-7998
mwatzke@cfa.harvard.edu
Ryan Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
Lane.e.figueroa@nasa.gov