A very rare pair of stars is behaving very strangely, according to scientists

According to the researchers who discovered it, a newly discovered very rare binary star system appears to be behaving very strangely.

The system is so unusual that there are thought to be only about 10 of them in our vast Milky Way galaxy.

It has all the conditions to go ahead and trigger a celagov, or the explosion that occurs when neutron stars collide, triggering an ultra-powerful explosion that can be detected across the universe.

“We know there are at least 100 billion stars in the Milky Way and probably hundreds of billions more. This amazing binary system is essentially a one-in-ten-billion system,” said NOIRLab astronomer and co-author of the new study, André-Nicolas Chené. “Prior to our study, the estimate was that there should only be one or two such systems in a spiral galaxy like the Milky Way.”

The twin star system is bright in X-rays and high in mass, say the astronomers who discovered it. But it is highly unusual because the two stars will orbit each other in what they say is a “strangely circular” way.

It appears to have been formed when an exploding star or supernova went out, rather than exploding with the usual dramatic burst.

Their strange orbits helped researchers determine that one of the two stars was a “consumed” supernova. That meant that when the star used up its fuel, and its core collapsed, there was a relatively weak explosion.

Usually, that explosion starts the stars into long elliptical orbits. But there wasn’t even enough energy left in the star to create such an explosion, so the two stars remained closely aligned in a circular orbit.

Over time, they will merge, sending powerful gravitational waves through the cosmos and leaving behind heavy elements like silver and gold.

The pair of stars is quite strange in itself. But scientists hope that finding a system like this could help us better understand kilonovae, those dramatic explosions that are also thought to be the source of gold in the universe.

“For quite some time, astronomers have been speculating about the exact conditions that could lead to a Chilean nova,” said Dr Chené. “These new results show that, at least in some cases, two sibling neutron stars can merge when one of them was created without a classic supernova explosion.”

The system is called CPD-29 2176, and it is located about 11,400 light years from Earth. It was first spotted by NASA’s Neil Gehrels Swift Observatory and later observations using the 1.5-meter SMARTS Telescope in Chile confirmed its unusual nature.

The findings are described in a new paper, published in the journal nature today, under the title ‘High-mass X-ray binaries from an ultra-strip supernova’.

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