Astronomers have discovered evidence of a runaway black hole, giving us what could be the first known evidence that supermassive black holes can be ejected from their home galaxies. The researchers publishing their findings on arXiv.org, though it has been accepted to The Astrophysical Journal Letters. According to those findings, a supermassive black hole was removed from its galaxy and is roaming interstellar space.
It’s an intriguing discovery, and one that sits up there with the fact that rogue black holes exist. The discovery was made when astronomers noted a bright streak of light while observing RCP 28, a dwarf galaxy roughly 7. 5 billion light-years from Earth. The first sign of a runaway black hole was discovered by Hubble’s astronomers, who observed the galaxy using Hubble.
Further observations of the galaxy showed that the bright streak of light was roughly 200,000 light-years long. That’s twice the width of our own Milky Way galaxy. It is thought that the streak may be composed of compressed gas, which could actively form new stars. Following the streak, the astronomers discovered a runaway black hole estimated to measure 20 million times the mass of the Sun.
The newly discovered black hole is currently speeding away from its home galaxy at around 3. 5 million miles per hour (5. 6 million km/h) – roughly 4,000 times the speed of sound. The most striking thing is the fact that the streak from the black hole runs back to the centre of the galaxy. Of course, confirming that the streak is being left behind by a black hole was important.
Black holes often eject streams of material into space, known as astrophysical jets. These jets matched what astronomers saw in the bright streak of light, so they had to determine if that was the cause or if the streak had actually been left behind by a runaway black hole kicked from its home galaxy. The researchers say the streak didn’t contain the tell-tale markers of an astrophysical jet.
One big difference between the two is the fact that the streak doesn’t get weaker as it travels further from its galaxy. Instead, it’s actually getting stronger, giving more evidence that it could be a runaway black hole storming through interstellar space. How does a blackhole get out of its galaxy? It could be caused by another black hole entering a binary system and causing one or more cosmic entities to be expelled outward.
Astronomers aren’t sure how common these runaway black holes might be. Perhaps we’ll find evidence of other black holes like this as we observe the universe more.
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