Supernova explosions could damage distant planets

Most previous studies on the effects of supernova explosions focused on the dangers from two periods – the massive radiation produced by a supernova in the days and months following the explosion, and the energetic particles arriving hundreds to thousands of years afterwards. 

Now, by using observations from NASA’s Chandra X-ray Observatory and other telescopes, a team of astronomers led by the University of Illinois Urbana-Champaign has found that between these two previously identified dangers lurks another one: if a supernova’s blast wave happens to strike dense surrounding gas, it can produce massive doses of X-rays that can severely damage the atmospheres of planets up to 160 light-years away.

“If a torrent of X-rays sweeps over a nearby planet, the radiation would severely alter the planet’s atmospheric chemistry,” said lead author Ian Brunton, a research scientist at the NASA Johnson Space Flight Center and former student at Illinois. “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.”

According to the experts, if a planet with Earth’s biology were hit with such sustained high-energy radiation from a nearby supernova, a wide range of organisms would vanish – particularly in marine ecosystems at the foundation of the food chain – and likely initiate a mass extinction.

“The Earth is not in any danger from an event like this now because there are no potential supernovae within the X-ray danger zone,” said co-author Connor O’Mahoney, a Physics and Astronomy student at Illinois. “However, it may be the case that such events played a role in Earth’s past.”

For instance, the detection in different regions around the world of a radioactive type of iron suggests that supernovae likely occurred close to our planet between two and eight million years ago. Although such evidence does not tie supernovae to any particular mass extinction event on Earth, it does suggest that cosmic explosions have probably affected our planet during its history. In fact, since our solar system is located in the so-called “Local Bubble” – a hot, low-density region in space thought to be a product of many supernovae explosions about 14 million years ago – the chance for Earth to have been exposed to massive radiation bursts from supernovae is quite significant.

Although our planet and solar system are currently in a safe space in terms of potential supernovae explosions, various other planets in the Milky Way where conditions may be conducive to life are not. Thus, better understanding the complexity of effects of supernovae explosions could not only shed new light on the life cycle of stars, but also help us better understand which areas of our galaxy may potentially harbor life.

The study is published in The Astrophysical Journal. 

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By Andrei Ionescu, Earth.com Staff Writer

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