• Astronomers have determined that supernova explosions pose another threat to planets and their atmospheres.
• This result comes from the analysis of X-ray observations for more than 30 supernovae using
  Nasa
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  ” data-gt-translate-attributes=”[{” attribute=””>NASA’s Chandra X-ray Observatory and other telescopes.

• For some types of supernova the researchers found that a torrent of X-rays could be unleashed that last for decades.
• This type of X-ray onslaught could significantly damage atmospheres of nearby planets, impacting life as we know it.
• Earth is in a safe space in terms of potentially harmful supernova explosions, but may not have been in the past.

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 in which intense X-rays from exploded stars can affect planets more than 100 light years away. This result has implications for the study of exoplanets and their habitability.

This newly discovered threat comes from the shock wave from a supernova 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 dose of X-rays that hits an Earth-like planet (shown at bottom left, lit by its host star out of view at right) 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 noting this threat is based on X-ray observations of 31 supernovae and their aftermath – mostly from NASA’s Chandra X-ray Observatory, Swift and

” data-gt-translate-attributes=”[{” attribute=””>NuSTAR missions, and ESA’s XMM-Newton — show that planets can be subjected to lethal doses of radiation located as much as about 160 light-years away. Four of the supernovae in the study (SN 1979C, SN 1987A, SN 2010jl, and SN 1994I) are shown in composite images containing Chandra data in the supplemental images below.

SN 1979C. Credit: NASA/CXC/M. Weiss

SN 1987A. Credit: NASA/CXC/M. Weiss

SN 2010jl. Credit: NASA/CXC/M. Weiss

SN 1994I. Credit: NASA/CXC/M. Weiss

Prior to this, most research on the effects of supernova explosions had focused on the danger from two periods: the intense radiation produced by a supernova in the days and months after the explosion, and the energetic particles that arrive hundreds to thousands of years afterward.

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, as shown in the illustration. A “de-greening” of land masses could also occur because of damage to plants.

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

A separate artist’s impression (panel #1) depicts the same Earth-like planet as having been abundant with life at the time of the nearby supernova, years before most of the X-ray’s impacts are felt (panel #2).

Among the four supernovae in the set of images, SN 2010jl 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.

Although Earth and the solar system are currently in safe space in terms of potential supernova explosions, many other planets in the

” data-gt-translate-attributes=”[{” attribute=””>Milky Way are not. These high-energy events would effectively shrink the areas within the Milky Way galaxy, known as the Galactic Habitable Zone, where conditions would be conducive for life as we know it.

Because the X-ray observations of supernovae are sparse, particularly of the variety that strongly interact with their surroundings, the authors urge follow-up observations of interacting supernovae for months and years after the explosion.

Reference: “X-Ray-luminous Supernovae: Threats to Terrestrial Biospheres” by Ian R. Brunton, Connor O’Mahoney, Brian D. Fields, Adrian L. Melott and Brian C. Thomas, 19 April 2023, The