Wolf 359’s extreme radiation and frequent X-ray flares make life-sustaining atmospheres on nearby planets highly unlikely, limiting their habitability.
- Astronomers have studied how intense space weather from a nearby star could impact any orbiting planets.
- Wolf 359, a red dwarf, is one of the most common types of stars in the universe and can burn for trillions of years.
- Researchers used NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton to analyze the high-energy radiation emitted by Wolf 359.
- Their findings suggest that only a planet located far enough from the star and covered in greenhouse gases might have a chance of sustaining life as we know it.
X-ray Radiation and Nearby Exoplanets
This illustration visualizes findings from a new study on how X-ray and high-energy radiation from a host star impact nearby exoplanets. Using NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton, astronomers studied Wolf 359, a red dwarf located just 7.8 light-years from Earth — one of the closest stars beyond our Sun.
The rendering depicts Wolf 359 in the foreground, with a potential orbiting planet in the background. Red dwarfs are the most common type of star in the universe. They are significantly smaller and dimmer than Sun-like stars but burn for trillions of years. This long lifespan gives any orbiting planets an extended window for life to potentially develop, making them prime targets for scientists searching for habitable worlds beyond our Solar System.
Can Planets Around Wolf 359 Support Life?
In the new study, researchers used Chandra and XMM to study the impact of steady X-ray and energetic ultraviolet (UV) radiation from Wolf 359 on the atmospheres of planets that might be orbiting the star. They found that only a planet with greenhouse gases like carbon dioxide in its atmosphere and at a relatively large distance away from Wolf 359 would have a chance to support life as we know it around a nearby star. The planet is depicted with the heavy cloud cover expected from the effects of greenhouse gases.
Their work suggests that just being far enough away from the star’s harmful radiation would not be enough to allow a planet around Wolf 359 to sustain life. The team looked at the “habitable zone,” the region around a star where liquid water could exist on a planet’s surface, for Wolf 359. They found that an Earth-like planet in the middle of the habitable zone blanketed with greenhouse gases should be able to sustain an atmosphere for almost two billion years.
Devastating X-ray Flares Threaten Atmospheres
In addition to the dangers posed by the steady, everyday high-energy radiation from a star like Wolf 359, any orbiting planets would be subjected to occasional giant bursts of X-rays. Using observations with Chandra and XMM-Newton, astronomers discovered 18 X-ray flares, or outbursts, from Wolf 359 in under 4 days. Chandra data of Wolf 359 is shown above.
Extrapolating from these observed flares, the team expects that much more powerful and damaging flares would occur over longer periods of time. The combined effects of the steady X-ray and UV radiation and the flares means that any planet located in the habitable zone is unlikely to have a significant atmosphere long enough for multicellular life, as we know it on Earth, to form and survive. (Evidence suggests that it took at least 3 billion years for multicellular life to emerge on Earth.) The exception is the habitable zone’s outer edge if a planet has a significant greenhouse effect.
This video shows a young, low-mass, relatively cool star called a red dwarf like Wolf 359. Because it is young, the star is very active and can flare several times a day. These flares are very hot and can include ejections of mass equivalent to that of a small moon. Around the star, we see a planet with roughly the same mass as Earth. Since the star is cool, the planet needs to be very close to its host star — only between 2.5 million and 5 million miles — in order to potentially maintain a temperature on its surface that would allow for liquid water. By comparison, the Earth orbits the Sun at a distance of about 93 million miles.
Innovative Techniques for Measuring UV Radiation
The researchers used a special technique to estimate the energetic UV radiation from Wolf 359 using Chandra. The team looked at the difference in radiation measured with the High Resolution Camera (HRC) using two different filters: first, a thick filter that allows only X-rays to be detected, and second, a thinner filter that allows both X-rays and UV radiation to be detected. There are currently no specialized space missions for studying the most energetic ultraviolet radiation.
These findings were presented at the 245th meeting of the American Astronomical Society in National Harbor, Maryland, and are being prepared for publication in a scientific journal. NASA’s Marshall Space Flight Center oversees the Chandra program, while the Smithsonian Astrophysical Observatory’s Chandra X-ray Center manages science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
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