Astronomers using data from NASA’s Chandra X-ray Observatory and other telescopes have identified a new threat to life on planets like Earth: a phase during which intense X-ray radiation from exploding stars can affect planets more than 100 light-years away. This result, as outlined in our latest press release, has implications for the study of exoplanets and their habitability.
This newfound threat comes from a supernova shock wave hitting the dense gas surrounding the exploded star, as shown in the upper right corner of our artist’s impression. When this impact occurs, it can produce a large burst of X-rays that reaches the Earth like planet months to years after the explosion and can last for decades. Such intense exposure can trigger an extinction event on the planet.
A new study reporting on this threat is based on X-ray observations of 31 supernovae and their aftermath mostly from NASA’s Chandra X-ray Observatory, ESA’s Swift and NuSTAR missions, and XMM-Newton that planets can be exposed to lethal doses of radiation found up to about 160 light- years away.
Previously, most research into the effects of supernova explosions focused on hazards from two periods: the intense radiation produced by the supernova in the days and months after the explosion, and the energetic particles that arrive hundreds to thousands of years later.
Found a new threat to Earth planet
If a stream of X-rays passes over a nearby planet, the radiation could seriously alter the chemistry of the planet’s atmosphere. For an Earth-like planet, this process could destroy a significant portion of the ozone, ultimately protecting life from its host star’s dangerous ultraviolet radiation. It could also lead to the extinction of a wide range of organisms, especially marine ones that form the base of the food chain, leading to extinction.
After years of lethal X-ray exposure due to the interaction of a supernova and the impact of ultraviolet radiation from the host star of an Earth-like planet, large amounts of nitrogen dioxide can be produced, causing brown haze in the atmosphere, as shown in the illustration. As a result of plant damage, land masses could also be “de-greened”.
Among the four supernovae in the image set, SN 2010jl produced the most X-rays. The authors estimate that it delivered a lethal dose of X-rays to Earth-like planets less than 100 light-years away.
There is strong evidence including detection of a radioactive type of iron at various locations around the world supernovae occurred near Earth between about 2 million and 8 million years ago. Researchers estimate that these supernovae were about 65 to 500 light-years away from Earth.
Although Earth and the Solar System are currently in a safe space for potential supernova explosions, many other planets in the Milky Way are not. These high-energy events would effectively shrink the regions in the Milky Way galaxy, known as the Galactic Habitable Zone, where conditions would be favorable for life as we know it.
Since X-ray observations of supernovae are rare, especially of the variety that interact strongly with their surroundings, the authors encourage follow-up observations of interacting supernovae months and years after the explosion.
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