A pair of Japanese astrophysicists wants to reveal millions of missing black holes hiding in our galaxy. The hidden black holes take matter from interstellar space, including dust and rocks floating around them and stars. They face various difficulties in this process, but a new paper aims to explain why scientists haven’t been so successful in revealing these black holes.
The researchers published their findings on the preprint website arXiv. They used x-rays to observe interstellar black holes (IBH,) but they wrote in their study that this is a “naïve way” because once a black hole sucks in matter from space, it accelerates at its corners and forms accretion disks. The matter in the disks rubs itself as it spins toward the event horizon, the point at which nothing that enters black hole can return.
However, isolated black holes (IBH) are significantly smaller than the supermassive black holes at the centers of galaxies, and they don’t emit x-rays that can be detected. Their accretion disks don’t generate enough energy to shoot out x-rays. Past researchers who focused on the search for IBHs with x-rays didn’t produce any fruitful results, which is why scientists believe there are millions of missing black holes in the Milky Way.
“These outflows can possibly make the IBHs detectable in other wavelengths,” researchers Daichi Tsuna of the University of Tokyo and Norita Kawanaka of Kyoto University wrote in their paper. “The outflows can interact with the surrounding matter and create strong collisionless shocks at the interface. These shocks can amplify magnetic fields and accelerate electrons, and these electrons emit synchrotron radiation in the radio wavelength.”
“Interesting paper,” Leiden University astrophysicist Simon Portegies Zwart, who was not involved in the study, told Live Science. “It would be a great way to find IMBHs. I think that with LOFAR [the Low-Frequency Array in the Netherlands], such research should already be possible, but the sensitivity may pose a problem.”
As Portegies Zwart explained, IBHs are seen as the “missing link” between the two different types of black holes that scientists can detect. The two types are stellar-mass black holes, which can measure up to 100 times the size of the sun, and supermassive black holes, which are colossal space beasts residing at the centers of galaxies, including the Milky Way. Now scientists want to uncover millions of missing black holes in the Milky Way.
Stellar-mass black holes can be occasionally detected in binary star systems with regular stars. Scientists have previously found that binary systems can emit gravitational waves that help them study dark matter and dark energy. On the other hand, supermassive black holes have incredibly powerful accretion disks which power their x-ray jets and gravitational waves.