New star hazard to planets identified by NASA’s Chandra program


April 21, 2023

(Nanowerk News) Exploding stars could pose more of a risk to nearby planets than previously thought, according to a new study from NASA’s Chandra X-ray Observatory and other X-ray telescopes. This newly identified threat involves an intense X-ray phase that can damage a planet’s atmosphere up to 160 light years away.

The results of the study, led by researchers at the University of Illinois Urbana-Champaign, Washburn University and the University of Kansas, are published in Astrophysics Journal (“X-Ray-luminous supernova: a threat to the terrestrial biosphere”). intense X-rays from exploding stars Astronomers using data from NASA’s Chandra X-ray Observatory and other telescopes have identified a new threat to life on Earth-like planets: a phase in which intense X-rays from exploding stars can affect planets more than 100 light years away. . (Graph: NASA/CXC/M.Weiss)

Earth is not in danger of such a threat today because there is no potential supernova ancestor within this distance, but it may have experienced this kind of exposure to X-rays in the past, scientists said.

Prior to this study, most research on the effects of supernova explosions focused on the hazard of two periods: the intense radiation that supernovas produce in the days and months after the explosion, and the energetic particles that arrive hundreds to thousands of years afterward.

However, even this alarming threat doesn’t completely catalog the dangers following a stellar explosion. Researchers have found that between these two previously identified hazards lurks another. The tail of a supernova always produces X-rays, but if the supernova blast wave strikes the denser gas around it, it can produce large doses of X-rays that arrive months to years after the explosion and can last for decades.

Calculations in the new study are based on X-ray observations of 31 supernovae and their consequences, most of which were obtained from Chandra, NASA’s Swift and NuSTAR missions, and the European Space Agency’s XMM-Newton mission. An analysis of these observations suggests that a supernova interacting with its environment could have dire consequences for a planet some 160 light years away.

“If a burst of X-rays swept over a nearby planet, the radiation would profoundly change the chemistry of the planet’s atmosphere,” said Ian Brunton, a former Illinois scholar now at NASA’s Johnson Space Flight Center and first author of the study. “For Earth-like planets, this process can eliminate most of the ozone, which in turn protects life from the harmful ultraviolet radiation from its host star.”

If a planet with Earth’s biology is exposed to sustained high-energy radiation from a nearby supernova, especially one that interacts heavily with its environment, it can cause the death of various organisms, especially in marine environments on the food floor. chain. This effect may be significant enough to initiate a mass extinction event.

“Earth is not in danger from an event like this right now because there are no potential supernovae within the X-ray danger zone,” said Illinois undergraduate student Connor O’Mahoney, one of the study’s authors. “However, it is possible that such events played a role in Earth’s past.”

There is strong evidence – including the detection of radioactive types of iron at various locations around the world – that a supernova occurred near Earth between about two and eight million years ago. Researchers estimate this supernova to be between about 65 and 500 light years from Earth.

Earth is in a “Local Bubble”, a still expanding bubble of hot, low-density gas surrounded by a shell of cold gas that spans about 1,000 light-years. The expansion of stars near the surface of the Local Bubble implies that it was formed from a star-forming explosion and a supernova near the center of the bubble about 14 million years ago, the researchers said.

The massive young stars responsible for the supernova explosions then were much closer to our planet than they are now, which put Earth at much higher risk of these supernovas in the past.

While this evidence doesn’t link the supernova to any specific mass extinction event on Earth, it does suggest that cosmic explosions have impacted our planet throughout its history, the researchers said.

The study reports that while Earth and the solar system are currently in the safe space of potential supernova explosions, many other planets in the Milky Way are not. This high-energy event would effectively shrink the area within the Milky Way galaxy, known as the Galactic Habitable Zone, where conditions are conducive to life.

Because X-ray observations of supernovae are rare, especially the varieties that strongly interact with their environment, the researchers say that follow-up observations of interacting supernovae months and years after the explosion will be invaluable.

“Further research into X-rays from supernovae is invaluable not only for understanding the life cycles of stars,” said astronomy professor Brian Fields, who directs the study portion at Illinois, “but also has implications for fields such as astrobiology, paleontology and Earth and planetary sciences.”


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