Are Tiny Black Holes Hiding Within Giant Stars?

sciencehabit shares a report from Science Magazine: Grunge music: a source of validation for a generation of disaffected youth. And a surprising source of scientific inspiration for Earl Bellinger of the Max Planck Institute for Astrophysics. While listening to Soundgarden's 1994 hit Black Hole Sun 2 years ago, he contemplated a curious question: Might itty-bitty black holes from the dawn of time be lurking in the hearts of giant stars? A new study by Bellinger and colleagues suggests the idea is not so far-fetched. Astronomers could detect these trapped black holes by the vibrations they cause on the star's surface. And if there's enough of them out there, they could function as the mysterious dark matter that holds the universe together.

The researchers found that the black holes would sink to the star's core where hydrogen atoms undergo fusion to produce heat and light. At first, very little would happen. Even a dense stellar core is mostly empty space. The most microscopic of the black holes would have a hard time finding matter to consume and its growth would be extremely slow, Bellinger says. 'It could take longer than the lifetime of the universe to eat the star.' But larger ones, roughly as massive as the asteroid Ceres or the dwarf planet Pluto, would get bigger on timescales of only a few hundred million years. Material would spiral onto the black hole, forming a disk that would heat up through friction and emit radiation. Once the black hole was about as massive as Earth, it would produce significant amounts of radiation, shining brightly and churning up the star's core like pot of boiling water. 'It will become a black hole -- powered object rather than fusion-powered object,' says study co-author Matt Caplan, a theoretical physicist at Illinois State University. He and his colleagues have dubbed these entities 'Hawking stars.'

The European Space Agency's Gaia satellite has spotted about 500 such anomalously cool giant stars, known as red stragglers, Bellinger says. To figure out whether these might actually be hiding a black hole, he says, astronomers could tune in to the particular frequencies at which the stars vibrate. Because a Hawking star would churn throughout its interior, rather than just in the topmost layers like an ordinary red giant, it would be expected to thrum with a particular combination of frequencies. Such waves can be detected in the way the star's light pulses and throbs. Bellinger is applying for funding to study the known red stragglers and see whether any display the characteristic vibrations of a black hole. The study has been published in The Astrophysical Journal.

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