7.04.2025

An extremely rare binary system involving high-mass white dwarf stars just 150 light-years away are on a collision course. When they collide, the type 1a supernova explosion will be 10 times brighter than the Moon.

The discovery of the doomed pair is described in a paper published in Nature Astronomy.

Type 1a supernovae are referred to as “standard candles” because astronomers know the brightness of these explosions. They are used by cosmologists to work out the distance between Earth and other galaxies and are even useful in testing theories about the expansion of the universe.

Type 1a supernovae occur when a white dwarf – the dense core left behind by a dead star – gathers too much mass.

Astronomers have long believed that the most common cause of a type 1a supernova is when 2 white dwarf stars get too close to each other. The heavier of the pair accumulates material from its partner through gravity, leading to one or both stars exploding.

But such a system has never actually been seen before now.

“For years a local and massive double white dwarf binary has been anticipated, so when I first spotted this system with a very high total mass on our galactic doorstep, I was immediately excited,” says study lead James Munday from the University of Warwick in the UK.

The stars are orbiting each other once roughly every 14 hours. But their leisurely encircling won’t last forever.

Over the next billion years, gravitational wave radiation will cause the stars to spiral closer together. When they are about to go supernova, the stars will be orbiting each other every 30–40 seconds.

This picture captures the binary in the moment where the first white dwarf has just exploded, hurtling material towards its nearby companion which is on the cusp of explosion too. In only 4 seconds do both stars explode. Credit: University of Warwick / Mark Garlick.

“With an international team of astronomers, 4 based at the University of Warwick, we immediately chased this system on some of the biggest optical telescopes in the world to determine exactly how compact it is.

“Discovering that the 2 stars are separated by just 1/60th of the Earth-Sun distance, I quickly realised that we had discovered the first double white dwarf binary that will undoubtedly lead to a type 1a supernova.”

The resulting explosion will be a thousand trillion trillion (1 with 27 zeroes after it) times that of the most powerful nuclear bomb.

Should we be worried given how close the doomed pair are to our solar system? No – the stars will go supernova in about 23 billion years according to the team’s calculations. For perspective you might like this article.

“Finding such a system on our galactic doorstep is an indication that they must be relatively common, otherwise we would have needed to look much further away, searching a larger volume of our galaxy, to encounter them,” says co-author Ingrid Pelisoli, also at Warwick.

“Finding this system is not the end of the story though, our survey searching for type 1a supernova progenitors is still ongoing and we expect more exciting discoveries in the future. Little by little we are getting closer to solving the mystery of the origin of type 1a explosions.”

Quelle: COSMOS