Cosmic Reanimator: Black Holes Can Jump-Start Nearby Dead Stars, Causing Them to Reignite

Friday, 31 August 2018 - 12:09PM
Space
Black Holes
Friday, 31 August 2018 - 12:09PM
Cosmic Reanimator: Black Holes Can Jump-Start Nearby Dead Stars, Causing Them to Reignite
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Image Credit: Caltech/JPL
Physicists have known for a while that the edge of a black hole is where the normal laws of the universe start to bend and warp—get too close and you'll start to undergo spaghettification (which is a real and terrifying scientific phenomenon), but stay just far enough away and you might be able to 'travel' through time. Bring a white dwarf close enough to a mid-sized black hole, though, and you might see a miracle: for a few brief seconds, the dead star will re-ignite and begin burning again.

In case you're not familiar, a white dwarf is one of the end stages of a star's lifespan: most stars like our own Sun start out burning hot, but after they exhaust all their gaseous fuel they start to swell in size, becoming a red giant, which eventually collapses and creates a nebula, then collapses even farther to create a white dwarf. Though the final collapse of larger stars sometimes ends in a supernova, most smaller ones just end up as inert, super-dense, roughly planet-sized white dwarfs that can no longer create fusion. After that, they spend the rest of their lifespans cooling off.

However, simulations run by a team led by Professor Chris Fragile from the College of Charleston have shown that when a white dwarf passes close to an intermediate-sized black hole (which has a mass ranging from 1,000 and 10,000 times that of the Sun), the intense gravitational forces can warp the matter inside the dwarf enough to trigger fusion again. Though it only lasts a short time, this re-ignition can cause a tidal disruption event, or TDE, which sends out gravitational waves, similar to the ones picked up by LIGO in September 2017.

Even more promising than the prospect of temporarily reviving dead stars, however, is picking up signals from one of these events. Mid-sized black holes are still poorly understood and hard to spot, so being able to sense gravitational waves from one of their TDEs would help astronomers find and study them. According to Fragile: "It is important to know how many intermediate mass black holes exist, as this will help answer the question of where supermassive black holes come from. Finding intermediate mass black holes through tidal disruption events would be a tremendous advancement."

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