Astronomers just confirmed the first black hole star: "We’re seeing pure black hole star light"

Since it became operational in 2022, the James Webb Space Telescope (JWST) has persistently detected small, luminous red points in its images of the early universe. Called Little Red Dots (LRDs) by astronomers, these entities have been found to be abundant in the universe's infancy but are entirely absent in the present day.

The true nature of these LRDs remained a mystery until very recently. Astronomers initially suspected these dots were early, heavily redshifted galaxies, but what they observed suggested otherwise. On one hand, these LRDs were found to shine with the light similar to that of giant stars, while on the other, they had the brightness typical of active galactic nuclei powered by supermassive black holes. With traditional models failing to provide a satisfactory answer to this mystery, astronomers hypothesized that these dots could be 'black hole stars'—an entirely new type of astrophysical object. In a study published in Nature on August 12, astronomers confirmed this hypothesis by identifying the clearest, farthest known object of this kind.

The image shows an illustration of a black hole star.

While there had been other black hole star candidates prior to the publication of the August 12 study, their light was mixed with their host galaxies, making it difficult for astronomers to gather a clean signature. This all changed when a team of researchers used data from the JWST's Mirage or Miracle (MoM) survey and identified MoM-BH*-1. The first officially designated black hole star, MoM-BH*-1 is so bright that it outshines its host galaxy, making it observationally "naked." This allowed astronomers to see its light without any contamination.

"...What is special about MoM-BH*-1 is, the black hole star is essentially completely outshining its surrounding host galaxy, such that we’re seeing pure black hole star light," said study lead author Dr. Rohan Naidu, commenting on the findings.

MoM-BH*-1 is an incredibly dense powerhouse. At 100,000 times the mass of the Sun, this intermediate-mass black hole is surrounded by a thick envelope of gas that spans a volume comparable to the entirety of our solar system. Furthermore, MoM-BH*-1 radiates roughly 100 billion times more energy than what any known star can produce through fusion.

"You have something that looks a bit like a star but is 100 billion times brighter. That means you can’t be powering this by nuclear fusion, which is the energy source that sits at the heart of all the stars we have," said Naidu

While black hole stars had been hypothesized to exist, MoM-BH*-1's discovery is empirical proof of their existence. And while the standard, modern stars we see today carry out nuclear fusion of hydrogen into helium, these black hole stars are powered by accretion—the intense frictional heat and energy generated by matter continuously falling into the gas-shrouded black hole.

Scores of LRDs have been spotted by the JWST to date, all in the early universe. Thanks to the discovery of MoM-BH*-1, we now know that almost all of these objects are likely to be black hole stars. “Every little red dot is consistent with being a black hole star, embedded in a generic early galaxy,” lead author Naidu said.

This drastically alters our understanding of the universe's evolution. Up until now, our models suggested that supermassive black holes formed inside mature galaxies and took billions of years to grow into the cosmic monsters we know today. However, the abundance of LRDs in images of the early universe tells us that supermassive black holes do not necessarily need mature host galaxies and billions of years to reach gigantic proportions.

This image shows some of the Little Red Dots (LRDs) observed by the James Webb Space Telescope (JWST).