Astronomers have uncovered a cosmic giant that could be the most massive black hole ever detected, a discovery that pushes the limits of what we thought possible about these mysterious celestial objects.
This newly measured ultramassive black hole tips the scales at a staggering 36 billion times the mass of our Sun, making it roughly 10,000 times heavier than the one lurking at the heart of the Milky Way.
Its home is the core of one of the universe’s largest known galaxies, a colossal system nicknamed the Cosmic Horseshoe, located around 5 billion light-years from Earth.
A Galaxy That Bends Light Into a Cosmic Ring
The galaxy earns its striking name from the way it bends light from an even more distant galaxy into a perfect horseshoe-shaped arc, known as an Einstein ring. This phenomenon, caused by the galaxy’s immense gravitational field, provided scientists with the perfect opportunity to spot the hidden black hole.
Researchers combined gravitational lensing, which is the bending of light by massive objects, with stellar kinematics, the motion of stars swirling around the black hole, to determine its extraordinary size. This dual approach allowed for one of the most precise measurements of a black hole’s mass ever recorded.
“This is among the top 10 most massive black holes ever found, and quite possibly the single most massive,” said Professor Thomas Collett of the University of Portsmouth, who led the study.
Unlike the raging, light-spewing quasars often associated with massive black holes, this one is “dormant.” It is not actively devouring matter or blazing with radiation. Instead, its presence is revealed only by its gravitational pull, bending light from far-off galaxies and propelling nearby stars at speeds close to 400 kilometres per second.
Unlocking Secrets of Galaxy and Black Hole Growth
Carlos Melo of the Universidade Federal do Rio Grande do Sul in Brazil, a co-author of the study, called the method a breakthrough. By combining these two lines of evidence, astronomers can now detect and measure hidden black holes that remain silent in the cosmic dark.
The find also provides important clues about the relationship between galaxies and the black holes at their centers. Larger galaxies tend to host larger black holes, and the Cosmic Horseshoe appears to be a “fossil group” galaxy. This means it is the final stage of multiple large galaxies merging into one, with their central black holes eventually fusing into a single, colossal object.
For comparison, the Milky Way’s central black hole weighs in at a relatively modest four million solar masses. It is also dormant today but has a history of quasar activity and the potential to become active again in the future.
The technique used in this research could help uncover many more ultramassive black holes in distant parts of the universe. Upcoming observatories, such as the European Space Agency’s Euclid space telescope, may soon offer new insights into how these cosmic giants form and evolve.