Data from NASA’s Chandra X-ray Observatory have helped identify a new threat to Earth: intense X-rays from exploding stars

The explosions that occur when a star dies may have more serious consequences for planets like ours than previously thought, a new study suggests. According to the researchers, the intense radiation caused by such an explosion can negatively affect the atmospheres of exoplanets located at distances of up to 160 light years, possibly triggering an extinction event.

Studies on this topic to date have focused on the intense radiation produced during the first days and months of a supernova—an extremely violent explosion that occurs at the end of a massive star’s life—and on the way in which the energetic particles can reach a nearby exoplanet hundreds or even thousands of years later.

Now, researchers have analyzed X-ray data emitted by 31 supernovae and their aftermath—mostly from NASA’s Chandra X-ray Observatory, the Swift and NuSTAR missions, and ESA’s XMM-Newton—and have identified a period of time after the death of these stars that is highly dangerous.

“Much of this research has focused primarily on atmospheric damage associated with the early arrival of ionizing photons within days to months of the initial burst and high-energy cosmic rays arriving thousands of years after the explosion,” they write. the researchers in an article published in The Astrophysical Journal. The study shows that planets can be subjected to lethal doses of radiation coming from up to 160 light-years away.

How would it affect a planet like ours? When a supernova explodes, its shock wave impacts against the dense gas that surrounds the star that has exploded. This impact, the researchers say, can produce the emission of a large amount of X-rays that reaches the planets months or years after the explosion and can continue to affect them for several decades.

“If a torrent of X-rays sweeps across a nearby planet, the radiation could seriously alter the planet’s atmospheric chemistry,” says the US space agency. “In the case of an Earth-like planet, this process could deplete a significant part of the ozone, which ultimately protects life from dangerous ultraviolet radiation from its host star. It can also cause a wide range of organisms to disappear, especially marine ones that are at the bottom of the food chain, leading to an extinction event.”

NASA researchers say that after years of exposure to these deadly X-rays and the impact of ultraviolet radiation from their star, a large amount of nitrogen dioxide could be produced, causing a brown haze in the atmosphere. This, as shown in the illustration that opens this article, can cause damage to plants causing a “greening” of the planet.

Less chance of finding life NASA points out that there is evidence indicating that supernovae occurred near Earth between two and eight million years ago. The researchers calculate that these supernovae were between 65 and 500 light years from Earth.

Although there is currently no record of supernovae near Earth, there is a possibility that the planet was exposed to their intense radiation in the past.

However, many other planets in the Milky Way may have been affected, reducing the number of places where conditions are conducive to life as we know it, a region called the Galactic Habitable Zone and that this new studio becomes even smaller.

source: https://iopscience.iop.org/article/10.3847/1538-4357/acc728