The upside of volatile space weather

Although violent and invisible, planetary star-studded flames do not prevent life from forming, according to a new study from Northwestern University.

Inlaid with stars, stellar flames are like sudden flares of magnetic images. On Earth, solar flames sometimes damage satellites and disrupt radio communications. Elsewhere in the universe, strong stellar flames have the ability to release and destroy atmospheric gases, such as ozone. Without the ozone, harmful levels of ultraviolet (UV) radiation can pass through a planet’s atmosphere, thus reducing the chance of harboring surface life.

Combining 3D atmospheric chemistry and climate modeling with flare data seen from distant stars, a team led by Northwestern found that stellar flames could play an important role in the long-term evolution of atmosphere and space- planetary residence.

“We compared the atmospheric chemistry of planets that often suffered from flames with planets without flames. The chemistry of the long-term atmosphere is very different,” said Howard Chen of Northwestern, the study’s first author. “Continuous flames will indeed drive the fusion of a planet’s atmosphere into a new chemical equilibrium.”

“We have found that large flames may not prevent the existence of life,” said Daniel Horton, lead author of the study. “In some cases, erosion doesn’t erode all the atmospheric ozone. Surface life may still have a chance to fight off.”

The study will be published on December 21 in the journal Astronomy of nature. It is a collaborative effort among researchers at Northwestern, the University of Colorado at Boulder, the University of Chicago, the Massachusetts Institute of Technology and NASA Nexus for Exoplanet System Science (NExSS).

Horton is an assistant professor of Earth and planetary sciences at Weinberg Northwestern College of Arts and Sciences. Chen is a Ph.D. a candidate in the Horton Climate Change Study Group and a future NASA researcher.

The importance of flames

All the stars – including our own sun – light up, or release energy at random. Fortunately for Earthlings, the planet is usually unaffected by solar flames.

“Our sun is more of a calm giant,” said Allison Youngblood, an astronomer at the University of Colorado and co-author of the study. “It’s older and less active than younger and smaller stars. Earth also has a strong magnetic field, which avoids the sun’s destructive winds.”

Unfortunately, most exoplanets that are capable of living are not so fortunate. For planets to have potential life, they need to be close enough to a star that their water won’t freeze – but they’re not so close that water spoils.

“We studied changing planets within the cultivated zones of dwarf stars M and K – the most common stars in the universe,” Horton said. “Normal zones around these stars are narrower because the stars are smaller and more powerful than stars like our sun. On the flip side, dwarf stars M and K with spy activity are thought to be more frequent than our sun, and their fast-locked planets are unlike magnetic fields to help reduce their high winds. “

Chen and Horton previously studied the long-term average climate of stellar M systems. Flames, however, occur on time frames of hours or days. While these short timeframes may be difficult to simulate, the inclusion of the effects of flames is important to create a more complete picture of exoplanet atmospheres. The researchers achieved this by incorporating flare data from NASA’s Satellite Exoplanet Transiting Study, launched in 2018, into their model simulations.

Using flames to find life

If there is life on these rugged exoplanets M and K, previous work suggests that stellar flames could make them easier to detect. For example, stellar flames can increase the abundance of life-signaling gases (such as nitrogen dioxide, nitous oxide and nitric acid) from invisible to visible levels.

“Space weather events are usually viewed as a negative impact on living capacity,” Chen said. “But our study conclusively shows that some space climates can help us find signatures of important gases that may signal biological processes.”

This study included researchers from a wide range of backgrounds and experiences, including climate scientists, exoplanet scientists, astronauts, theorists and observers.

“This project was the result of an incredible team effort,” said Eric T. Wolf, planetary scientist at CU Boulder and co-author of the study. “Our work highlights the benefits of interdisciplinary efforts when studying conditions on extrasolar planets.”

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The study, “Flare-driven atmosphere chemistry world sustainability,” was supported by NASA’s Graduate Research Award for Earth and Space Science and Technology (no. 80NSSC19K1523).