Black Holes Can Raise the Cosmic Dead
Adding a cosmic
"Walking Dead" twist to the most morbid of all space objects,
scientists have found that some black holes could bring dead "zombie"
stars back to life — and then destroy them.
Black holes are
invisible "objects" in space where the gravity is so strong that it
sucks everything into it, even light. All of the black holes that astronomers
have found so far are either superbig — as in hundreds of thousands and even
billions of times the mass of our sun — or on the smallish side, as in, say,
less than 100 times the mass of our sun. Astronomers haven't spotted any of
these matter-sucking beasts in the middle range yet, but that doesn't mean they
don't exist.
Scientists at Lawrence
Livermore National Laboratory in California suspect that midsize black holes
might be just the right size to provide enough gravitational force to reignite
a dead white dwarf star — the stellar corpse of a star that's about the mass of
the sun and that's used up its nuclear fuel.
To test their idea, the
team members ran supercomputer simulations of dozens of different
close-encounter scenarios between these dead stars and midsize black holes.
Every time a white dwarf got close to the Goldilocks black hole, the star
reignited. The gravitational force from the black hole would cause the stellar
material to fuse into varying amounts of calcium and iron, producing more
fusion and iron as the star got closer to the black hole. This so-called
nucleosynthesis process would reignite the once-dead star.
The team also found
that the star's revival would create powerful electromagnetic waves that could
be picked up by detectors in near-Earth orbit — meaning we might be able to
"see" where it happened and find the medium-size black hole that gave
it a second life.
"If the stars
align, so to speak, a zombie star could serve as a homing beacon for a
never-before-detected class of black holes," Peter Anninos, physicist and
lead author on the study, said in a statement.
But the resurrected
star wouldn't stay bright forever. The necromancing black hole would bring the
star back to life — only to rip it apart later.
"As [the spherical
star] approaches the black hole, tidal forces begin to compress the star in a
direction perpendicular to the orbital plane, reigniting it," physicist
Rob Hoffman, co-author on the study, said in the statement. "But within
the orbital plane, these gravitational forces stretch the star and tear it
apart.”
The team published its
findings in the September issue of The Astrophysical Journal.
source:
https://www.livescience.com/63984-black-holes-revive-zombie-stars.html
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