Almost every massive galaxy hosts a supermassive black hole at its central region. When two galaxies join together, their black holes can create a binary pair, a system where they are in a bound orbit with one another.
It has been hypothesized that these binary pairs are fated to merge, although this has never been observed. For several years, the question of whether such an event will likely happen has been a topic of debate among astronomers.
Dynamics of Black Hole Duo
In a recent study, a team of researchers has presented new insight into the mystery of black hole merging. Their findings are discussed in the paper "The Central Kinematics and Black Hole Mass of 4C+37.11".
Led by Tirth Surti, the scientists focused on a supermassive black hole binary located within the elliptical galaxy B2 0402+379. To analyze this system, they used data provided by the Gemini North telescope in Hawai'i.
This pair is the only supermassive black hole binary ever explored in enough detail to see both members separately. At only 24 light-years, it also holds the record for having the smallest separation process ever measured directly. Although this close separation predicted a powerful merger, further study also revealed that the duo has been stalled at this distance for more than three billion years.
To gain more insight on the dynamics of the binary system and its halted merger, the astronomers looked to archival data provided by Gemini North's Gemini Multi-Object Spectrograph (GMOS). The data enabled them to determine the speed of the stars within the surrounding area of the black holes.
The excellent sensitivity of GMOS allowed the researchers to trace the increasing velocities of the stars as one looks closer to the center of the galaxy. From here, the scientists can infer the total mass of the black holes residing in the central region.
Surti and colleagues estimate the mass of the black hole binary to be a whopping 28 billion times that of the Sun. This qualifies the pair as the heaviest black hole ever measured. The measurement can offer valuable context to the formation of the binary system as well as the history of its host galaxy. Additionally, it supports the theory that the mass of a supermassive binary black hole can contribute in hindering a potential merger.
Understanding Galactic Merging
The insight on the formation of this binary can help in predicting if and when it will join together. As a matter of fact, several clues point to the black hole pair formation through multiple galaxy mergers.
Aside from their large combined mass, the presence of two supermassive black holes suggests that the binary resulted from the amalgamation of multiple smaller black holes from several galaxies.
After a galactic merger, supermassive black holes do not collide head-on. Instead, they begin to slingshot past each other as they settle into a bound orbit. For every pass they make, energy is transferred from the black holes to the surrounding stars. As they lose energy in the process, the duo is dragged down closer until they are just light-years apart, in areas where gravitational radiation takes over and allows them to merge.
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