by Supernovas are bad news. They can destroy biospheres and flood planets with deadly radiation. And now, a recent study has added a potential new threat: a special type of supernova that can destroy a planet’s ozone layer years after the initial explosion.
When giant stars die in massive explosions called supernova, they temporarily become some of the brightest objects in the universe. A single supernova can eclipse the combined light of hundreds of billions of stars.
To give you some perspective, the nearby star Betelgeuse will explode any day. (That’s an astronomical “any day,” meaning within the next few million years.) Even though the star is more than 600 light-years away from us, when it will go supernova , it will be the brightest object in our sky, just behind the Sun. Betelgeuse will be visible during the day, shining brighter than a full moon. For a few weeks, at the height of the explosion, it will be so bright that it will cast shadows in the middle of the night.
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Despite the dreadful luminosity, the visible light portion of a supernova is only a tiny fraction of the total energy output. Also, although intense amounts of visible light can cause blindness, they don’t have many other serious effects. What is more concerning is the high-energy radiation associated with the supernova, usually in the form of X-rays and gamma rays.
X-ray specifications
High-energy radiation can catalyze oxygen, stripping away Earth’s protective ozone layer. Without the ozone layer, life on the surface of our planet would experience the full ultraviolet radiation of the sun, which could lead to an extinction event.
The burst of radiation occurs within the first seconds of a supernova, but an even greater threat arises later. cosmic rayswhich are subatomic particles accelerated to nearly speed of light, eventually erupted from the maelstrom hundreds or thousands of years later. They carry a decent fraction of the supernova’s total energy with them, and they can also strip away ozone layers and drench a planet’s surface in deadly radiation.
Such events may have occurred in the past. Analysis of lunar regolith and submarine cores reveals substantial amounts of iron-60, a radioactive isotope of iron produced only in supernovae. The presence of iron-60 suggests that the Earth was hit by supernova ejecta just a few million years ago.
Based on the threats posed by gamma rays and cosmic rays, astronomers have already concluded that we are relatively safe; there are no nearby supernova candidates that may pose a threat to life on Earth.
But astronomers have discovered a potential new hazard, which they described in a paper published in the Preprint Database. arXiv October: A certain class of supernova can release an additional form of deadly long-range radiation that poses a serious danger to Earth-like planets.
This special class of supernova occurs when a star approaching the end of its life is surrounded by a thick disc of material. After the initial supernova explosion, a shock wave forms and slams into this disk. The shock wave heats the disk to incredibly high temperatures, causing the disk to emit large amounts of X-rays.
This radiation can carry large amounts of energy and travel extremely long distances. In the recent study, astronomers found that the brightest X-ray supernovae can overwhelm a planet’s ozone layer, depleting it by up to 50%, which is more than enough to trigger an event. of extinction, at an incredible distance of 150 light-years.
Reduction of the galactic habitable zone
These types of supernovae would create a deadly double whammy. Months or years after the initial explosion, a vulnerable planet would be hammered by X-rays. Then, hundreds or thousands of years later, cosmic rays would come, finishing the job before the biosphere had had the chance to recover and replenish its protective layer.
Fortunately, Earth remains safe, as we don’t know of any candidate X-ray supernova nearby. But this new study places additional limits on the galactic habitable zone, the region of each galaxy that can support life. Within the confines of a galaxy, star formation is too weak to provide the necessary ingredients for rocky planets. But dense cores, where stars live and die at a breakneck pace, are also deadly, as frequent supernovae flood their surroundings with radiation.
The new study shows that the inner edge of the galactic habitable zone is likely farther from the galaxy’s core than we previously thought. Despite being hit here and there, Earth is in one of the safest neighborhoods in the entire galaxy.
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