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-rays from exploded stars can affect planets over 100 light-years away. This result, as outlined in our latest press release, has implication for the study of exoplanets and their habitability.
This newly found threat comes from a
supernova’s blast wave striking dense gas surrounding the exploded star, as
depicted in the upper right of our artist’s impression. When this impact occurs
it can produce a large dose of X-rays that reaches an Earth-like planet (shown
in the lower left, illuminated by its host star out of view to the right)
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 is based
on X-ray observations of 31 supernovae and their aftermath — mostly from NASA’s
Chandra X-ray Observatory, Swift and 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 image.
4 of the 31 supernovas in the
study. Credits: NASA/CXC/Univ. of Illinois/I. Brunton et al.
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.
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).
Illustration of an Earth-like
planet before and after radiation exposure. Credits: NASA/CXC/M. Weiss
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 the Earth and the Solar
System are currently in a safe space in terms of potential supernova
explosions, many other planets in the 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.
The paper describing this result
appears in the April 20, 2023 issue of The Astrophysical Journal, and is available here. The other authors of the paper
are Ian Brunton, Connor O’Mahoney, and Brian Fields (University of Illinois at
Urbana-Champaign), Adrian Melott (University of Kansas), and Brian Thomas
(Washburn University in Kansas).
NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Image credit: Science:
NASA/CXC/Univ. of Illinois/I. Brunton et al.; Illustration: NASA/CXC/M. Weiss
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X-ray Observatory.
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and related materials, visit: http://www.nasa.gov/chandra
Source: New Stellar Danger to Planets Identified by NASA's Chandra | NASA
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