Millions of High-Speed Black Holes Could Be Zooming Around The Milky Way
“Natal Kicks” sounds like a great name for a band or a bad thing to happen during childbirth, but it’s actually an astrophysics term for the velocity at birth of a black hole. If you’re looking for something else to keep you awake at night besides the latest political news, the latest astrophysics news tells us that there may be millions of black holes with a very high natal kick velocity speeding around our galaxy and looking for stars and planets to consume. Sweet dreams.
“This work basically talks about the first observational evidence that you can actually see black holes moving with high velocities in the galaxy and associate it to the kick the black hole system received at birth.”
ScienceAlert brings us the news of a new study about natal kicks and more accepted by the Monthly Notices of the Royal Astronomical Society. Co-author Pikky Atri (a top contender for Best Name for an Astronomer) explains the good news that she and her colleagues at Curtin University in Western Australia have found a way to track black holes feeding off of their partner in a binary system and follow their history back to their origin. Feeding black holes are the only ones astronomers can track because, although they can’t be seen, they belch X-rays and radio waves that can be picked up by telescopes.
“We tracked how these systems were moving in our galaxy – so, figured out their velocities today, moved back in time, and tried to understand what the velocity was of the system when it was born, individually for each of these 16 systems. Based on the velocities, you can actually find out if they were born with a supernova explosion, or if the stars just directly collapsed onto themselves without a supernova explosion.”
It’s been commonly accepted that black holes form when an elderly star implodes into itself. While it was known they could also form as the result of a sideways kick out of a particular type of supernova explosion that is lopsided, the number of these types of natal or Blaauw kicks births of black holes was a mystery. Atri found 16 binaries with feeding black holes and backtracked them to their births. She and her team then measured their velocities and trajectories and found that 12 of them showed the high speed and erratic movement which indicated that they were born by natal kick. Twelve. That’s not so bad, is it?
That’s 75 percent of the sample. If this scales up to the estimated 10 million black holes in the Milky Way, that might mean around 7.5 million high-speed black holes careening out there. And 10 million is a low estimate.
Thanks a lot, ScienceAlert. That’s a lot of hungry black holes in the Milky Way … and there’s probably more. Fortunately, Pikky Atri brings some astronomer logic to comfort us.
“The closest black hole, we think it’s two kiloparsecs away [6,523 light-years]. It’s very, very far away. So there’s no chance that we’re getting sucked up by any black hole any time soon.”
We would have felt better with “no chance” had she not added “we think” and “anytime soon.” Still, it’s big news that astronomers are getting better at tracking black holes as they travel around the universe. Perhaps by the time one gets close, we’ll have a better early warning system and deflection/destruction plan than our current asteroid watchers do.
And now, let’s give it up for the Natal Kicks!