The astronomers found that only a planet with greenhouse gases in an Earth-like atmosphere and relatively far from the star they studied would have a chance of supporting life as we know it around a nearby star.
Wolf 359 is a red dwarf with about one-tenth the mass of the Sun. Red dwarf stars are the most common stars in the Universe and live for billions of years, giving life plenty of time to develop. At only 7.8 light-years away, Wolf 359 is one of the closest stars to the Solar System.
“Wolf 359 could help us unlock the mysteries surrounding stars and habitability,” said Scott Wolk of the Center for Astrophysics. Harvard and Smithsonian (CfA), who led the study. “It’s so close and belongs to such an important class of stars — it’s a perfect combination.”
Because red dwarfs are the most common type of star, astronomers have worked hard to find exoplanets around them. Astronomers using optical telescopes have found some evidence for two planets orbiting Wolf 359, but these findings have been challenged by other scientists.
“Although we do not yet have evidence of planets around Wolf 359, it appears to host multiple planets,” Volk added. “This makes it a great test bed to see what planets around this type of star would experience.”
Wolk and his colleagues used Chandra and the XMM to study the amount of stable X-ray and extreme ultraviolet (UV) radiation — the most energetic type of UV radiation — that Wolf 359 emits at potential planets around it. will leave
They found that Wolf 359 is producing enough harmful radiation that only a planet with an atmosphere rich in greenhouse gases like carbon dioxide — and located relatively far from the star — could possibly support life. will happen
“Being far enough away from a star’s harmful radiation would not be enough to make it habitable,” said CFA co-author Vinay Kashyap. “A planet around Wolf 359 would need to vent as much greenhouse gas as Earth.”
To study the effects of energetic 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 the planet’s surface.
The outer limit of the habitable zone for Wolf 359 is about 15% of the distance between Earth and the Sun, as the red dwarf is much less luminous than the Sun. None of the planet candidates for this system are located in Wolf 359’s habitable zone, with one being too close to the star and the other too far away.
“If the inner planet is there, X-rays and extreme UV radiation would destroy the planet’s atmosphere in just a million years,” said co-author Ignazio Pelletieri of the CFA and National Institute for Astrophysics. Will do.” Palermo, Italy.
The team also considered the effects of radiation on as-yet-unidentified planets within the habitable zone. They concluded that an Earth-like planet in the middle of the habitable zone should be able to maintain an atmosphere for about two billion years, while a planet near the outer edge could persist indefinitely, supported by Greenhouse gases increase in heat.
Another major threat to planets orbiting stars like Wolf 359 is X-ray flares, or occasional bright bursts of X-rays, on top of the constant, daily output from the star. Combining observations with Chandra and XMM-Newton resulted in the discovery of 18 X-ray flares from Wolf 359 over 3.5 days.
Extrapolating from these observed flares, the team expects much more powerful and damaging flares over longer periods of time. The combined effects of persistent X-ray and UV 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 to survive. The exception is the outer edge of the habitable zone if the planet has a significant greenhouse effect.
These results were presented in 245Th 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 from Cambridge, Massachusetts and flight operations from Burlington, Massachusetts.
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Megan Watzke
Chandra X-ray Centre
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov