An image of LRG 3-757, known as the “Cosmic Horseshoe,” taken by the Hubble Space Telescope. (Image credit: NASA, ESA)
Astronomers have identified a gigantic black hole the size of 36 billion suns hiding in the “Cosmic Horseshoe.” The colossal object is one of the largest black holes ever discovered.
First discovered in 2007, the Cosmic Horseshoe is a pair of galaxies located in the constellation Leo. Images of the system show a halo of light surrounding the foreground galaxy, LRG 3-757. Known as an Einstein ring, this phenomenon occurs when the galaxy's significant mass distorts and amplifies the light from a more distant galaxy behind it.
This magnifying process is called gravitational lensing, and was first predicted by Albert Einstein in 1915. New research has shown how LRG 3-757 gets the mass it needs to distort light: from the enormous supermassive black hole at its center. The researchers posted their results on February 19 on the preprint server arXiv, meaning they have not yet been peer-reviewed.
Einstein's general theory of relativity describes how massive objects warp the fabric of the universe, known as space-time. Gravity, Einstein discovered, is not the result of an invisible force, but is a consequence of the distortion and warping of space-time in the presence of matter and energy.
This distorted space, in turn, sets rules for the movement of energy and matter. Although light travels in a straight line, light passing through a highly distorted region of space-time, such as around a massive galaxy, also moves in a curved path — looping around the galaxy and blurring into a halo.
To search for evidence of a black hole inside the Cosmic Horseshoe, astronomers used data obtained by the Multi Unit Spectroscopic Explorer spectrograph in the Chilean Atacama Desert, as well as images taken by the Hubble Space Telescope.
By analyzing the powerful gravitational lensing of LRG 3-757, a galaxy 100 times the mass of the Milky Way, and studying the speed and motion patterns of stars around it, the researchers concluded that the presence of a supermassive black hole “is required to simultaneously fit both sets of data.”
The discovery places LRG 3-757's black hole among the largest ever discovered. The largest, known as Ton 618, is estimated to weigh 66 billion solar masses and extends to a distance of up to 40 times the distance between Neptune and the Sun. While the black hole at the center of the Holm 15A galaxy cluster has a mass of 44 billion solar masses and extends to a distance of up to 30 times the distance between Neptune and the Sun.
Supermassive Mystery
Astronomers have not yet investigated how exactly the giant black hole LRG 3-757 formed. But the stars orbiting it move relatively slowly, and their movements are less random than would be expected for a black hole of its size.
This could be because some of the stars near it were ejected by previous galaxy mergers, or because the black hole once had powerful jets that suppressed star formation, or because the black hole rapidly gobbled up many of the stars around it early in its life.
Astronomers hope to get some answers to these questions with the Euclid space telescope, which is a year into its six-year mission to catalog a third of the entire night sky, taking thousands of wide-angle images. Eventually, Euclid will capture light from more than one billion galaxies that are as old as
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