Supernova showers: a deadly rain of X-rays threatens the planets

supernova planet

A new study has looked at the possible impact X-rays could have on planets some distance from supernova explosions. Data from Chandra and other telescopes suggests that planets around 160 light-years away could be subjected to an intense wave of X-rays, which could significantly damage their atmospheres. This artist’s illustration shows such an affected planet in the foreground months to years after the explosion (seen in the background) after it has been bombarded with X-rays, along with a second panel that shows the planet just as the supernova is going off. The study suggests that the areas of the Milky Way galaxy where conditions would be conducive to life as we know it would be smaller. Credit: NASA/CXC/M. Weiss

New research reveals that supernovae may pose an additional, previously unidentified threat to nearby planets. It involves intense X-rays, generated when a supernova shock wave hits the surrounding dense gas, potentially damaging the atmospheres of planets up to 160 light-years away and potentially leading to mass extinction events. The Earth is not currently at risk, but may have been exposed to such exposure in the past.

An exploded star may pose more risk to nearby planets than previously thought, according to a new study by[{” attribute=””>NASA’s Chandra X-ray Observatory and other X-ray telescopes. This newly identified threat involves a phase of intense X-rays that can damage the atmospheres of planets up to 160 light-years away.

Earth is not in danger of such a threat today because there are no potential supernova progenitors within this distance, but it may have experienced this kind of X-ray exposure in the past.

Before this study, most research on the effects of supernova explosions had focused on the danger from two periods: the intense radiation produced by a supernova in the days and months after the explosion, and the energetic particles that arrive hundreds to thousands of years afterward.

However, even these alarming threats do not fully catalog the dangers in the wake of an exploded star. Researchers have discovered that, in between these two previously identified dangers, lurks another. The aftermaths of supernovae always produce X-rays, but if the supernova’s blast wave strikes dense surrounding gas, it can produce a particularly large dose of X-rays that arrives months to years after the explosion and may last for decades.

The calculations in this latest study are based on X-ray observations of 31 supernovae and their aftermath mostly obtained from Chandra, NASA’s Swift and NuSTAR missions, and ESA’s (European Space Agency’s) XMM-Newton. The analysis of these observations shows that there can be lethal consequences from supernovae interacting with their surroundings, for planets located as much as about 160 light-years away.

“If a torrent of X-rays swept over a nearby planet, the radiation would severely alter the planet’s atmospheric chemistry,” said Ian Brunton of the University of Illinois at Urbana-Champaign who led the study. “For an Earth-like planet, this process could wipe out a significant portion of the ozone, which ultimately protects life from the dangerous ultraviolet radiation of its host star.”

If a planet with Earth’s biology were struck by sustained high-energy radiation from a nearby supernova, especially one strongly interacting with its surroundings, it could wipe out a wide range of organisms, especially marine organisms at the base of the food chain. . These effects can be large enough to trigger a mass extinction event.

“Earth is not at risk from an event like this now, because there are no potential supernovae in the X-ray danger zone,” said co-author Connor O’Mahoney, also from the University of Illinois. “However, such events may have played a role in Earth’s past.”

There is strong evidence – including detections in different locations around the globe of a type of radioactive iron – that supernovae occurred near Earth around two to eight million years ago. Researchers estimate that these supernovae were between about 65 and 500 light-years from Earth.

Planet before and after supernova

Illustration of an Earth-like planet before and after radiation exposure. Credit: NASA/CXC/M. Weiss

Earth is in the “local bubble,” an ever-expanding bubble of low-density hot gas surrounded by a shell of cold gas that spans about 1,000 light-years. The outward expansion of stars near the surface of the local bubble implies that it formed from an explosion of star formation and supernovae near the center of the bubble about 14 years ago. millions of years. The massive young stars responsible for supernova explosions were much closer to our planet then than those stars are now, which put Earth at a much higher risk of such supernovae in the past.

Although this evidence does not link supernovae to any particular mass extinction event on Earth, it does suggest that cosmic explosions have affected our planet throughout its history.

Although Earth and the solar system are currently in safe space in terms of potential supernova explosions, many other planets in the[{” attribute=””>Milky Way are not. These high-energy events would effectively shrink the areas within the Milky Way galaxy, known as the Galactic Habitable Zone, where conditions would be conducive for life as we know it.

Because the X-ray observations of supernovae are sparse, particularly of the variety that strongly interact with their surroundings, the authors argue that follow-up observations of interacting supernovae for months and years after the explosion would be valuable.

“Further research on X-rays from supernovae is valuable not just for understanding the life cycle of stars,” said co-author Brian Fields of the University of Illinois, “but also has implications for fields like astrobiology, paleontology, and the earth and planetary sciences.”

The paper describing this result appears in the April 20, 2023 issue of The Astrophysical Journal. The other co-authors of the paper are Adrian Melott from the University of Kansas and Brian Thomas from Washburn University in Kansas.

For more on this study, see NASA’s Chandra Unmasks New Cosmic Threat to Planetary Life.

Reference: “X-Ray-luminous Supernovae: Threats to Terrestrial Biospheres” by Ian R. Brunton, Connor O’Mahoney, Brian D. Fields, Adrian L. Melott and Brian C. Thomas, 19 April 2023, The Astrophysical Journal.
DOI: 10.3847/1538-4357/acc728

NASA’s Marshall Space Flight Center 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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