Reviewed by Lexie CornerSep 10 2024
NASA scientists have discovered the closest confirmed pair of supermassive black holes, located about 300 light-years apart, using NASA's Chandra X-ray Observatory and Hubble Space Telescope. These black holes, described as akin to two Sumo wrestlers facing off, are deep within two colliding galaxies. Due to the infalling gas and dust, they shine brightly as active galactic nuclei (AGN). The study has been published in The Astrophysical Journal.
This is an artist's depiction of a pair of active black holes at the heart of two merging galaxies. They are both surrounded by an accretion disk of hot gas. Some of the material is ejected along the spin axis of each black hole. Confined by powerful magnetic fields, the jets blaze across space at nearly the speed of light as devastating energy beams. Image Credit: NASA, ESA, Joseph Olmsted (STScI)
This AGN pair is the closest found in the local universe through multiwavelength measurements, combining visible and X-ray radiation. While several hundred "dual" black holes have been previously observed, their separations are significantly higher than in the gas-rich galaxy MCG-03-34-64. Although astronomers have discovered one pair of binary black holes in closer proximity using radio telescopes, confirmation at other frequencies was lacking.
AGN binaries like this were likely more common in the early universe when galaxy mergers occurred more frequently. This discovery provides a rare, close-up view of a neighboring example, about 800 million light-years away.
The finding was unexpected. Hubble's high-resolution imaging revealed three optical diffraction spikes within the host galaxy, indicating a dense concentration of blazing oxygen gas in a confined region.
We were not expecting to see something like this. This view is not a common occurrence in the nearby universe, and told us there's something else going on inside the galaxy.
Anna Trindade Falcão, Study Lead Author, Center for Astrophysics|Harvard & Smithsonian, NASA
Diffraction spikes are image artifacts that occur when light from a small region in space bends around a telescope's internal mirrors. Falcão's team used NASA's Chandra observatory to study the same galaxy, MCG-03-34-64, in X-rays to better understand its structure.
Falcão explained, “When we looked at MCG-03-34-64 in the X-ray band, we saw two separated, powerful sources of high-energy emission coincident with the bright optical points of light seen with Hubble. We put these pieces together and concluded that we were likely looking at two closely spaced supermassive black holes.”
The team's conclusion was based on archival radio data from the Karl G. Jansky Very Large Array in Socorro, New Mexico. The powerful black hole pair also emits strong radio waves.
“When you see bright light in optical, X-rays, and radio wavelengths, a lot of things can be ruled out, leaving the conclusion these can only be explained as close black holes. When you put all the pieces together, it gives you the picture of the AGN duo,” stated Falcão.
A third bright light source observed by Hubble remains unexplained. It could be gas-shocked by a jet of ultra-high-speed plasma from one of the black holes, similar to how a stream of water from a garden hose impacts a mound of sand. More data is needed to fully understand its nature.
Falcão added, “We wouldn't be able to see all of these intricacies without Hubble's amazing resolution.”
The two supermassive black holes originally resided at the centers of their respective host galaxies. A merger between these galaxies brought the black holes closer together, and they will continue spiraling inward until they eventually collide—possibly in about 100 million years. This collision will produce gravitational waves that ripple through space and time.
While the National Science Foundation's Laser Interferometer Gravitational-Wave Observatory (LIGO) has detected gravitational waves from hundreds of stellar-mass black hole mergers, the longer wavelengths produced by merging supermassive black holes are beyond LIGO's current detection capabilities.
The next-generation gravitational wave detector, the Laser Interferometer Space Antenna (LISA) project, aims to capture these longer wavelength gravitational waves. LISA will consist of three space-based detectors separated by millions of kilometers, capable of detecting gravitational waves from deep space. This project, led by the European Space Agency (ESA) in collaboration with NASA and other partners, is set to launch in the mid-2030s.
NASA's Marshall Space Flight Center manages the Chandra program, with the Smithsonian Astrophysical Observatory overseeing science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts. Northrop Grumman Space Technologies of Redondo Beach, California, was the principal contractor for the spacecraft.
NASA’s Hubble, Chandra Find Supermassive Black Hole Duo
In a surprise finding, astronomers, using NASA’s Hubble Space Telescope have discovered that the jet from a supermassive black hole at the core of M87, a huge galaxy 54 million light years away, seems to cause stars to erupt along its trajectory. The stars, called novae, are not caught inside the jet, but in a dangerous area near it. Video Credit: NASA's Goddard Space Flight Center; Lead Producer: Paul Morris
Journal Reference:
Falcão, T, A., et al. (2024) Resolving a Candidate Dual Active Galactic Nucleus with ∼100 pc Separation in MCG-03-34-64. The Astrophysical Journal. doi.org/10.3847/1538-4357/ad6b91