New Stellar Danger

Astronomers have identified a new threat to life on planets like Earth: a phase during which intense X-rays from exploded stars can affect planets over 100 light-years away.

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

This newly found threat comes from a supernova’s blast wave striking dense gas surrounding the exploded star.

When this impact occurs it can produce a large dose of X-rays that reaches an Earth-like planet months to years after the explosion and may last for decades.

Such intense exposure may trigger an extinction event on the planet.

A new study reporting this threat show that planets can be subjected to lethal doses of radiation located as much as about 160 light-years away.

If a torrent of X-rays sweeps over a nearby planet, the radiation could severely alter the planet's atmospheric chemistry.

For an Earth-like planet, this process could wipe out a significant portion of ozone, which ultimately protects life from the dangerous ultraviolet radiation of its host star.

It could also lead to the demise of a wide range of organisms, especially marine ones at the foundation of the food chain, leading to an extinction event.

After years of lethal X-ray exposure from the supernova’s interaction, and the impact of ultraviolet radiation from an Earth-like planet’s host star, a large amount of nitrogen dioxide may be produced, causing a brown haze in the atmosphere.

A “de-greening” of land masses could also occur because of damage to plants.

SN 2010jl supernova has produced the most X-rays.

The authors estimate it to have delivered a lethal dose of X-rays for Earth-like planets less than about 100 light-years away.

There is strong evidence — including the detection in different locations around the globe of a radioactive type of iron — that supernovae occurred close to Earth between about 2 million and 8 million years ago.

Researchers estimate these supernovae were between about 65 and 500 light-years away from Earth. (NASA)

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