Unprecedented discovery in the history of astronomy

Astronomers have discovered a bizarre binary star system consisting of two white dwarfs—dead, extremely dense stellar cores—that is being drawn into a cruel fate: a type 1a supernova explosion with four consecutive explosions never before recorded, according to a study published in Nature Astronomy.

These two white dwarfs are in a binary system – meaning they are gravitationally bound together – in the Milky Way, just 160 light-years from Earth.

Although their sizes are only comparable or slightly larger than Earth's, their masses are enormous: one star is 83% the mass of the Sun, and the other is 72%.

According to researcher James Munday working at the University of Warwick (UK) - the lead author of the study, this is the pair of white dwarfs with the largest total mass ever discovered.

The two stars orbit each other every 14 hours, so quickly that the distance between them is 25 times smaller than the distance between Mercury and the Sun. That distance is shrinking as the system loses energy—a slow process that takes billions of years.

And then, fate calls. Once the two dwarfs get close enough, the heavier star – due to its stronger gravitational pull – will begin to pull material from the lighter star.

When the mass increases beyond the allowable threshold, the two stars will trigger a violent thermonuclear chain reaction, creating a type 1a supernova explosion, this time not just one but four consecutive explosions.

“A white dwarf has a layered structure like an onion: a core of carbon and oxygen, surrounded by a layer of helium and a layer of hydrogen,” explains astronomer Ingrid Pelisoli, co-author of the study. “When the lighter star transfers mass to the heavier star, the heavier star’s helium layer becomes too thick, causing the first explosion. The resulting shockwave triggers a second explosion in the carbon-oxygen core. Then the lighter star explodes in the same way – helium first, then the carbon-oxygen core.”

According to scientists ' calculations, all of that will take place in less than 4 seconds and is expected to happen in about 22.6 billion years. At that time, if the Earth - currently only 4.5 billion years old - still exists, we will witness a halo 10 times brighter than the Moon in the night sky.

Mr. James Munday said that if the distance between the two stars was farther, they might have been at ease and not collided.

“In a larger orbit, they could have been perfectly stable without any disaster. But this time, we know for sure that the explosion will happen and will light up a part of the Milky Way,” he said.

(Vietnam News Agency/Vietnam+)

Source: https://www.vietnamplus.vn/phat-hien-chua-tung-co-trong-lich-su-thien-van-hoc-post1025413.vnp