What is the safe distance from supernovae?
The artist's conceptual conception of a supernova or explosive star.
(Image: David Aguilar/ Smithsonian Insider)
In the event of such a star explosion, if The Earth wants to survive, what is the safe distance from the supernova? - Please read on.
What is the safe distance from a supernova?
A supernova is a violent explosion of a massive star at the end of its life. If our Sun exploded as a supernova, the shock wave and heat generated would not burn the entire Earth, but the side of the Earth facing the Sun would evaporate. Scientists estimate that the temperature of the entire Earth will rise to about 15 times the normal surface temperature of the sun. More seriously, Earth will not be able to remain in its current orbit. A sharp drop in the sun's mass could cause the planet to get out of control and drift freely into space. Obviously, if the Sun supernova explodes, then the distance between the Earth and the Sun, which takes 8 minutes for light, is certainly not safe. Fortunately, though, our Sun is not the kind of star destined to explode. But other stars outside the solar system may, so what is the minimum safe distance? According to NASA, a supernova explosion can only feel its devastating effects within 50 light-years of Earth.
What happens if a supernova explodes near Earth?
So let's imagine a star exploding at an unsafe distance from Earth. For example, this supernova is 30 light-years away. Mark Reid, a senior astronomer at the Harvard-Smithsonian Center for Astrophysics, said:
...... If a supernova erupts within 30 light-years of ours, it would have a huge impact on Earth and could lead to mass extinctions. X-rays and high-energy gamma rays from supernovae destroy the ozone layer, which is supposed to protect us from the sun's ultraviolet rays, and at the same time, ionize nitrogen and oxygen in the atmosphere, resulting in a large amount of smoke-like nitrous oxide.
In addition, if a supernova erupts within 30 light-years, plankton and reef communities will be particularly affected, which will severely deplete the bottom layer of the ocean's food chain.
Then suppose the explosion is a little farther away. This would allow the Planet as a whole to survive, with surface life on land and sea surviving in relative integrity. But any relatively recent explosion would still throw large amounts of gamma rays and other high-energy radiation at Earth. This radiation may cause genetic mutations in Earth's organisms and alter our climate.
Fortunately, according to observational analysis, no star within 50 light-years of Earth is about to evolve into a supernova.
Zoom in view | The artist's conceptual conception of a supernova.
Image credit: NASA/European Southern Observatory
A supernova not so long ago
In known human history, no supernova has ever been found to have erupted within 50 light-years of ours. The most recent supernova explosion visible to the naked eye was supernova 1987A in 1987. It is about 168,000 light-years away.
Prior to that, the last supernova visible to the naked eye was recorded by Johannes Kepler in 1604. It's about 20,000 light-years away, brighter than any star in the night sky, even seen during the day! But as far as we know, it has no impact on the planet.
In 2011, the Hubble Space Telescope took an optical wavelength image of the wreckage of supernova 1987A. The supernova is the closest in centuries and can be seen with the naked eye alone. It is located at the edge of the Spider Nebula in the Great Magellanic Galaxy (a satellite galaxy of the Milky Way). It is about 168,000 light-years from Earth.
Image credit: NASA/European Space Agency/P. Challis (Harvard Smithsonian Center for Space Physics)
How far away is the nearest star, which has the potential to become a supernova?
First, there are two different kinds of supernovae. A type II supernova is an aging and collapsing massive star that has no mass of such magnitude within 50 light-years of Earth; a type I supernova occurs when a small, faint white dwarf star collapses due to an injection of companion star material. These stars are dim and difficult to find, so we can't be sure exactly how many are around. There may be hundreds of them within 50 light years, but we don't know which one is about to explode.
IK Pegasi B is the closest known supernova precursor candidate. It is part of a binary system , located about 150 light-years from our Sun and solar system.
The system's main star, IK Pegasi A, is an ordinary main sequence star that is no different from our Sun. A potential Type I supernova is another star in the binary system, IK Pegasi B, a massive white dwarf star that is very small in size and extremely dense, and its distance from IK Pegasi A is closer than Mercury's distance to the Sun. When A star begins to evolve into a red giant , it is expected to increase in size by a large radius , and B star can accrete material from A star 's expanding gas envelope. When the mass of a B star grows large enough, it may collapse on its own and explode in the process as a supernova.
Size comparison: IK Pegasi A (left), small but massive IK Pegasi B (lower middle) and our sun (right). The smallest of these stars is our closest known supernova precursor candidate, about 150 light-years away.
Image credit: RJ Hall/Wikimedia Commons
So, what about Betelgeuse?
Whenever we focus on a supernova, there's one star that can't be ignored, and that's Betelgeuse, which is one of the brightest stars in our sky and is part of the famous constellation Orion. Betelgeuse is a superstar. Its brightness is very high.
However, such light comes at a cost. Betelgeuse is one of the most famous stars in the sky because it will one day explode. Fuel is consumed very quickly (relatively) due to Betelgeuse's enormous energy requirements, and in fact, Betelgeuse's lifespan is nearing its end. One day in the near future (astronomically speaking), it will run out of fuel, collapse toward the center under its own gravity, and then reverse outward, exploding violently in the form of a Type II supernova. When this happens, Betelgeuse will become extremely bright in a few weeks or months, perhaps as bright as a full moon, and visible in broad daylight.
When will this happen? Maybe not in our lifetime, but no one really knows. It could be tomorrow, or it could be a million years from now. When it does happen, we will witness an extremely spectacular astronomical event in the night sky, but life on Earth will not be harmed by it. Because Betelgeuse is too far from Earth, 430 light-years away.
Betelgeuse is the orange star on orion's left shoulder.
This photograph was taken by Rogerio Bernal André and is an astronomical photograph taken on October 23, 2010. (Image source: Wikimedia Commons)
How often do supernovae erupt in our galaxy?
No one knows. Scientists speculate that the high-energy radiation from supernovae has caused genetic mutations in Earth species and even humans.
One study suggests that a dangerous supernova event could occur near Earth every 15 million years. There is another theory: on average, every 240 million years, there will be a supernova explosion, occurring within 10 parsecs (33 light-years) from Earth. So you see, we're really not sure about the law of supernova explosions. But you can compare that data to the millions of years that humans have existed and the 4.5 billion years of the Earth's age.
If you do, you'll find that there must have been supernovae erupting near Earth... But it may not be for the foreseeable future of humanity.
Finally, back to the topic: How far is the safe distance from supernovae? To survive, Earth must be at least 50 light-years away from the exploding star!
BY: earthsky
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