The Consequences of Introducing a Black Hole to the Sun

December 22, 2023

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By Max Planck Society

In a theoretical case, small primordial black holes could get trapped by nascent stars. The evolution of these so-called 'Hawking stars' has been modeled by an international team headed by researchers at the Max Planck Institute for Astrophysics. The team discovered that these stars can have unexpectedly long life spans, closely mimicking normal stars in several aspects. This research is published in The Astrophysical Journal.

Asteroseismology could assist in identifying such stars and could provide a testing ground for the existence of primordial black holes and their contribution to dark matter.

Expect a thought-provoking scientific exercise: What would happen to a star during its lifespan if, following the Big Bang, a large number of tiny black holes, or ‘primordial black holes’, were created and some were captured during the formation of new stars?

As per Selma de Mink, head of the stellar department at the Max Planck Institute for Astrophysics (MPA), scientists sometimes pose outlandish inquiries for further knowledge. Despite having no proof of their existence, a thought experiment regarding primordial black holes could be intriguing.

Primordial black holes, formed early in the universe, could vary in size from asteroids to those thousands of times the size of the sun. They could be integral to dark matter and could seed supermassive black holes in current galaxies.

A new star, on rare occasions, could capture a black hole the size of a small moon or an asteroid, which would then inhabit the star's center. This type of star is known as a 'Hawking star', an idea proposed by Stephen Hawking in a paper during the 1970s.

The black hole in a Hawking star would experience slow growth owing to the outgoing luminosity obstructing the gas intake needed to feed the black hole. A global team of scientists has modeled the development of such a star using various initial black hole masses and different accretion models for the star's core. To their amazement, a small black hole mass only renders the star virtually identical to a regular star.

Astonishingly, 'stars with a black hole at their core can have long lifespans,' states Earl Patrick Bellinger, MPA Postdoc, and now Assistant Professor at Yale University, who helmed the research. 'Our sun may even host a black hole as large as Mercury without us realizing.'

The main divergence between a normal star and a Hawking star would occur around the core, which could turn convective due to accretion onto the black hole. It would neither alter the star's surface properties nor would it be identifiable using existing detection capabilities. However, asteroseismology—a field that uses acoustic oscillations to examine the interior of a star—might detect it.

In their subsequent evolution, during the red giant phase, the black hole could create identifiable signatures. Upcoming ventures like PLATO might discover such objects, but further simulations need to be run to ascertain the consequences of introducing a black hole into stars of assorted masses and metallicity.

If primordial black holes were truly formed shortly after the Big Bang, the search for Hawking stars could lead to their discovery.

As Professor Matt Caplan at Illinois State University, a co-author of the study, indicates 'despite the sun being used for this exercise, there are solid reasons to assume that Hawking stars would be prevalent in globular clusters and ultra-faint dwarf galaxies.'

This implies that Hawking stars could serve as tools for verifying the existence of primordial black holes and their potential influence on dark matter.

Information regarding journal: Astrophysical Journal

Provided by Max Planck Society