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Astronomers Detect Binary System of White Dwarf Stars Set for Quadruple Detonation
In a groundbreaking astronomical discovery, scientists have identified a pair of closely orbiting white dwarf stars, the dense remnants of stars, within our Milky Way galaxy. This binary system is predicted to culminate in an extraordinarily powerful cosmic event: a quadruple detonation supernova.
Close Proximity of Stellar Remnants
These two white dwarf stars, bound together by gravity in a binary configuration, are located approximately 160 light-years from Earth. In astronomical terms, this distance is considered relatively nearby. A light-year, the distance light traverses in a year, equates to about 5.9 trillion miles (9.5 trillion kilometers).
Understanding White Dwarf Stars
White dwarfs represent the ultra-dense final stage in the life cycle of stars with up to eight times the mass of our Sun. As these stars exhaust their hydrogen fuel, gravity causes them to collapse. They expel their outer layers during a “red giant” phase, ultimately leaving behind a compact core – the white dwarf – roughly the size of Earth.
James Munday, the lead researcher of the study published in Nature Astronomy and a PhD candidate at the University of Warwick, UK, noted, “White dwarfs are the stellar leftovers of the majority of stars. Occasionally, we observe systems where two white dwarfs are in a tight orbit.”
Key Characteristics of the Binary System
Researchers analyzed data from four ground-based telescopes to scrutinize this particular binary system. One of the white dwarfs possesses a mass around 83% of our Sun’s, while the other is about 72%. According to Munday, this binary system has the largest combined mass known among white dwarf binaries.
Ingrid Pelisoli, an astrophysicist at the University of Warwick and co-author of the study, explained, “Both are roughly Earth-sized. One has a diameter approximately 20% larger, and the other about 50% larger, illustrating their incredible density. Imagine the Sun compressed to the size of Earth. When they were typical stars, their masses were likely three to four times that of the Sun.”
Orbits and Impending Collision
While hundreds of binary systems composed of two white dwarf stars are known, this pair exhibits the closest orbit observed thus far. They are approximately 25 times closer to each other than Mercury is to the Sun, completing an orbit in roughly 14 hours.
The distance between them is gradually decreasing as the system loses energy. Their significant mass and close proximity guarantee their eventual dramatic demise on a long timescale.
The Quadruple Detonation Sequence
As the white dwarfs draw nearer, the more massive one will exert stronger gravitational force, pulling material from the outer layers of its lighter companion. This mass transfer will cause the heavier white dwarf to exceed a critical mass limit, triggering a thermonuclear explosion.
This event will initiate a complex type 1a supernova, characterized in this instance by a quadruple detonation.
Pelisoli described the process: “White dwarfs have a layered structure, similar to an onion. They contain a carbon-oxygen core, surrounded by a helium layer, and finally a hydrogen layer.”
“As the less massive star transfers material to its heavier partner, the helium layer of the more massive star becomes overly dense, sparking an initial explosion. This first detonation then sets off a second explosion in the carbon-oxygen core. The resulting shockwaves from these initial explosions then trigger a third explosion in the remaining helium layer of the companion star, which in turn ignites a fourth explosion in its carbon-oxygen core,” Pelisoli elaborated.
Timeline of the Cosmic Event
This extraordinary quadruple detonation is projected to unfold in approximately four seconds from beginning to end. However, this event is not imminent.
Researchers estimate that the quadruple detonation will occur roughly 22.6 billion years in the future. For context, the universe is currently about 13.8 billion years old. When the explosion does occur, it would appear from Earth to be about ten times brighter than the Moon in the night sky—assuming Earth, currently around 4.5 billion years old, still exists.
Significance of the Discovery
This marks the first identification of a binary system destined for such a spectacular end. Had the white dwarfs been more distantly separated, preventing mass transfer, they could have persisted indefinitely in a stable state.
“In a wider orbit, they could indeed exist stably without a catastrophic future, but in this case, we know that the explosion will illuminate our region of the galaxy,” Munday concluded.