Astronomers have discovered a runaway supermassive black hole, leading to the formation of a wake of shocked gas and young stars behind it.
The black hole in question was seemingly ejected from its home galaxy and offers the first evidence of the phenomenon.
According to research, accepted for publication in The Astrophysical Journal Letters, the researchers made the ‘serendipitous discovery’ as they spotted the runaway black hole as a bright streak of light while observing the dwarf galaxy RCP 28 on the Hubble Space Telescope.
Follow-up observations showed that the streak measures more than 200,000 light-years long — roughly twice the width of the Milky Way.
The streak is thought to be made of compressed gas that is actively forming stars and points to the centre of a galaxy, where a supermassive black hole would sit.
Researchers believe that the black hole attached to the streak, is nearly 20 million times the mass of the sun and is speeding away from its home galaxy at 3.5 million mph (5.6 million km/h). That’s almost 4,500 times the speed of sound.
‘We found a thin line in a Hubble image that is pointing to the centre of a galaxy,’ lead study author Pieter van Dokkum, a professor of physics and astronomy at Yale University, told Live Science.
‘Using the Keck telescope in Hawaii, we found that the line and the galaxy are connected. From a detailed analysis of the feature, we inferred that we are seeing a very massive black hole that was ejected from the galaxy, leaving a trail of gas and newly formed stars in its wake.’
Most large galaxies host active supermassive black holes at their centres which often launch jets of material at high speeds. These appear as streaks of light called ‘astrophysical jets’.
To make sure that the streak they spotted wasn’t an astrophysical jet, the team further investigated it and found that, unlike astrophysical jets that grow weaker as they move away from their source of emission, this one got stronger as it moved away from its point of origin.
The team concluded that the explanation that best fits the streak is a supermassive black hole blasting through the gas that surrounds its galaxy.
‘If confirmed, it would be the first time that we have clear evidence that supermassive black holes can escape from galaxies,’ van Dokkum said
Researchers believe that the black hole could have been ejected due to a galactic merger where a third black hole ousted this one.
So, the runaway black hole might have once been part of a rare supermassive black hole binary that was disrupted.
Further observations with other telescopes are needed to confirm that it is indeed a black hole at the tip of the mysterious streak.
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