In an exciting development for the field of astrophysics, astronomers have uncovered the presence of two massive white dwarf stars that are orbiting closely together in a binary system, situated approximately 160 light-years away from Earth in the Milky Way galaxy. This remarkable stellar pairing is destined for an extraordinary demise characterized by a quadruple explosion, a phenomenon not previously documented in such a system.

White dwarfs are among the universe's most compact celestial objects, typically formed when stars with an initial mass up to eight times that of our Sun exhaust their hydrogen fuel. As these stars age, they undergo a transformation, swelling into a red giant before shedding their outer layers, ultimately leaving behind a dense core known as a white dwarf. Astronomers estimate that the mass of these two white dwarfs is significant, with one star weighing about 83% that of our Sun and the other around 72%.

James Munday, a PhD researcher at the University of Warwick and the lead author of the study, explained, “White dwarfs are the stellar remnants of the vast majority of stars, and from time to time we find systems where two white dwarfs closely orbit each other.” The study, highlighting this fascinating discovery, has been published in the prestigious journal Nature Astronomy.

Using data collected from four ground-based telescopes, researchers determined these two white dwarfs are the most massive known binary system of their kind. Notably, their diameters are comparable to that of Earth, with one being approximately 20% larger and the other 50% larger than our planet. This density illustrates just how compact these stellar remnants truly are. When they were in their earlier stages as regular stars, their masses were likely around three to four times that of our Sun, underscoring their immense gravitational forces.

This binary system is unique not only for its mass but also for its proximity. The two stars are positioned about 25 times closer to each other than the distance from Mercury, the innermost planet of our solar system, to the Sun. They complete an orbit approximately every 14 hours, and as they gradually lose orbital energy, their separation decreases, setting the stage for a violent future.

As the heavier white dwarf continues to draw material from its lighter companion due to its stronger gravitational pull, it will eventually accumulate enough mass to trigger a catastrophic thermonuclear explosion. This event is categorized as a type Ia supernova, which, in this case, will involve a complex series of detonations.

In a detailed explanation of the explosion mechanism, Pelisoli elaborated, “White dwarfs are made up of layers, much like an onion. Their inner layer is a core of carbon and oxygen, surrounded by a helium layer and finally by a hydrogen layer.” When the lighter star begins transferring mass to the heavier one, the helium layer will become increasingly massive, leading to an initial explosion. This event will subsequently trigger further explosions in the carbon-oxygen core of the heavier white dwarf, followed by additional detonations in the helium and carbon-oxygen layers of the companion star.

Researchers estimate that this remarkable quadruple detonation will occur approximately 22.6 billion years from now—far beyond the current age of the universe, which stands at around 13.8 billion years. In terms of visibility, when the explosions do happen, they would be seen from Earth as being ten times brighter than a full moon, assuming Earth still exists at that distant point in the future.

This discovery marks the first identification of a binary system poised for such a volatile end. Munday noted that if the two white dwarfs were situated farther apart, they could continue their existence without the risk of a catastrophic explosion. However, their current configuration guarantees that when the time comes, their demise will light up a significant portion of our galaxy.