Potential Life on Red Dwarf Planets In Peril Due To Extreme Space Weather

David A. Aguilar (CfA)

When solar wind interacts our planet’s magnetic field, it creates beautiful aurorae in our atmosphere. A new study has revealed that for exoplanets around red-dwarf stars, the amount of solar activity would obliterate the planet’s atmosphere, virtually eliminating any chance of finding extraterrestrial life on rocky planets in those locations. Unfortunately, it is those very planets that astronomers have been targeting when seeking life. The research was led by a team at the Harvard-Smithsonian Center for Astrophysics (CfA) and the results were presented today at the 224th Meeting of the American Astronomical Society in Boston.

About 80% of all stars in the known Universe are red dwarf stars, which range from 0.075-0.5 solar masses. For this reason, they’ve been a popular target for astronomers to look for exoplanets as possible homes for extraterrestrial life. However, since the stars are much smaller and colder than our sun, the habitable zone is considerably closer, which puts the planets much closer to the solar activity. This hampers the possibility of finding life at these locations.

"A red-dwarf planet faces an extreme space environment, in addition to other stresses like tidal locking," said Ofer Cohen of CfA in a press release.

Earth is about 93 million miles away from the Sun, which provides a nice buffer and dissipates some of the effects of solar wind before it gets to us. Our capable magnetic field bounces off the solar wind that does reach us, kind of like a forcefield. Rocky planets around red-dwarf stars do not have the same luxury.

The researchers utilized a computer program created at the University of Michigan to run the simulations of how the solar activity of a middle-aged red-dwarf star would interact with the atmosphere of a rocky planet in its habitable zone. The results weren’t great. Even a magnetic field on par with Earth’s isn’t enough to protect it, as it turns out. While there were moments of time when the magnetic field offered good protection, but it was relatively short lived. 

"The space environment of close-in exoplanets is much more extreme than what the Earth faces," co-author Jeremy Drake explains. "The ultimate consequence is that any planet potentially would have its atmosphere stripped over time.”

If there is an upside to this harsh solar activity, it is that aurorae on these planets would be about 100,000 times greater than what we see on Earth. The intense lights wouldn’t just be visible near the poles, but would reach halfway down to the planet’s equator as well. Too bad nobody is there to see it. Although, all that beauty comes at a very steep price.

“If Earth were orbiting a red dwarf, then people in Boston would get to see the Northern Lights every night," Cohen said. "Oh the other hand, we'd also be in constant darkness because of tidal locking, and blasted by hurricane-force winds because of the dayside-nightside temperature contrast. I don't think even hardy New Englanders want to face that kind of weather."

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