Astronomers Discover The First Wandering Black Hole In Milky Way
In what can be called yet another massive space discovery, a team of astronomers has detailed the discovery of the first-ever isolated stellar-mass black hole just wandering its way through the Milky Way galaxy. In 2019, scientists reported spotting a Jupiter-sized black hole passing through the galaxy that the Earth calls home. Last year, a study published in the Monthly Notices of the Royal Astronomical Society journal claimed that wandering giant black holes may be lurking around the galactic halos.
Galaxies the size of the Milky Way were touted to have about 12 such rogue black holes casually strolling along the outskirts. But so far, such a black hole's existence hasn't been verified using proper measurements and observation data. And that probably has to do with the fact that directly detecting a black hole wandering against the black backdrop of space is no cakewalk. However, it appears that a wandering black hole might also be making its way through the Milky Way galaxy and has just been spotted for the first time.
Name MOA-2011-BLG-191/OGLE-2011-BLG-0462, the black hole in question has a mass roughly seven times that of the sun. Local black holes are easier to detect as they shine bright due to the heated matter falling into them or when they collide and emit gravitational waves. For isolated black holes, the technique used to spot them is called gravitational lensing. And when a small object exhibits the phenomenon, it is classified as microlensing. In a nutshell, a large object like a black hole passing between a star and the observer bends the space around and warps light, making the star appear magnified or displaced from its actual position. In the case of the wandering MOA-2011-BLG-191/OGLE-2011-BLG-0462 black hole, scientists observed the lensing event eight times between 2011 and 2017 to see a deflection in the lensed star's position. The star observed for the study is located about 20,000 light-years away from Earth.
According to measurement data, scientists could calculate the wandering black hole's pace to about 45 kilometers per second. At that speed, the black hole is said to outpace most stars in its surroundings. A culmination of imaging duties by the Hubble Space Telescope over six years, scientists relied on the lensing technique to discover the massive black hole that is about 5,000 light-years away from the Earth. The team behind the discovery noticed that the lensed object did not emit any light while having a mass that is far beyond what a neutron star or white dwarf can achieve, leaving a black hole as the only candidate.
Titled "An Isolated Stellar-Mass Black Hole Detected Through Astrometric Microlensing," the paper adds that the wandering black hole may have received a "natal" kick from the supernova explosion that created it. However, it is unclear how old the black hole actually is. Scientists are now pinning their hopes on more advanced observation hardware such as the Vera C. Rubin Observatory in Chile (set to become operational in 2023) and NASA's Nancy Grace Roman Space Telescope (scheduled for launch in 2027) to collect more in-depth data about these free-floating black holes, how they are formed, and just how many of them are there lurking the Milky Way's backyard.
Source: arXiv