Astronomers detected two robust white wword stars – highly compact star embers – orbiting close to each other and apparently designed to die in extraordinarily violent quadruple detonation.
Gravitational linked to each other in what is called a binary system, the two stars are located in our galaxy, the Milky Way, about 160 light years from Earth-relatively close in cosmic terms. A light year is the distance that light travels in one year, or 9.5 trillion km.
White dwarfs are among the most compact celestial bodies. Stars up to eight times the mass of our sun seem to end this way: burning all the hydrogen they use as fuel. Gravity, then, makes them collapse and explode their outer layers on a “red giant” stage, leaving behind a compact nucleus with approximately the diameter of the earth – the white dwarf.
“White dwarfs are the stellar remnants of the vast majority of stars and, from time to time, we find systems where two white dweders orbit one around each other,” said James Munday, PhD researcher at Warwick University, England, and lead author of the study published in the journal Nature Astronomy.
The researchers used data from four terrestrial telescopes to study this binary system. One of the white dwarfs has a mass of about 83% of the mass of our sun and the other has about 72%. No other known white dwarf binary has a larger combined mass, Munday said.
“Both are almost as large as Earth. One has a diameter about 20% larger and the other about 50% larger. This gives us an idea of how dense they are. It is the sun’s size compressed. Its masses, when they were normal stars, were probably about three to four times the mass of the sun,” Warwick university astrophysics and study coauthor, Ingrid Pelisoli said.
A few hundred binary systems composed of two white wwords are known. These two orbit closest to each other than any other. They are about 25 times closer to each other than the innermost planet of our solar system, Mercury, is from the sun, completing an orbit every 14 hours.
As the distance between them gradually decreases as the binary system loses energy, the fact that they are so massive and so close guarantees its death on a large scale of time.
When they approach each other even more, the heaviest of the two white dwarfs, due to their greatest gravitational force, will begin to extract material from the lighter outer layer and increase its mass beyond the limit from which a white dwarf undergoes a thermonuclear explosion.
This will prepare the scenario for a complex explosion called Type 1A Supernova, which in this case involves a quadruple detonation.
“White dwarfs are composed of layers, such as an onion. Its inner layer is a carbon and oxygen core, surrounded by a layer of helium and finally by a hydrogen layer,” said Pelisoli.
“The less massive star will transfer mass to the mass when they begin to interact. This will cause the heavy helium layer to become very massive, causing an explosion. This then triggers a second explosion in the carbon-oxygen nucleus. The shock wave of these explosions, in turn, triggers a third explosion in the companion’s remaining helium layer, Which triggers a fourth explosion in its carbon-oxygen core, ”added Pelisoli.
This quadruple detonation is expected to take about four seconds from start to finish. But it will not happen anytime soon.
The researchers estimate that it will take place in approximately 22.6 billion years – the universe is about 13.8 billion years. When the explosion occurs, it will seem, from the perspective of the earth, about 10 times brighter than the moon in the night sky – if the earth, now about 4.5 billion years, still exists.
This is the first time a binary system that apparently has been heading for this destination has been identified. If the two white dweds were distant enough so that the heaviest would not suck the lighter material, they could survive in perpetual peace.
“In a wider orbit, they could indeed live stablely without any catastrophic future, but here we know that the explosion will illuminate our side of the galaxy,” Munday said.
See also: NASA Hubble Telescope Captures New Photo of the Galaxy
Explosive star event will create unique vision in the sky; understand
This content was originally published in astronomers foresee unpublished quadruple detonation of two white dwarfs on the CNN Brazil website.
Source: CNN Brasil

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