Up until recently, astronomers had only observed black holes in two sizes.
A black hole is an area in space with a gravitational force so strong matter, radiation and light cannot escape.
A stellar black hole is small and forms when a star collapses. It’s about the size of a small city. Then there are supermassive black holes which can be up to billions of times larger than Earth’s sun. Galaxies tend to revolve around these.
However, physicist Nelson Christensen, research director of the French National Centre for Scientific Research, discovered that black holes can actually merge to form stellar black holes bigger than 70 times the size of our sun.
“Two very massive black holes merged together and emit gravitational waves as they do so,” Christensen told the Associated Press. “Now we’ve seen black holes merge and produce gravitational waves already, but what’s interesting here is that this system is so massive.”
In May 2019, astronomers detected a signal that was the energy from two stellar black holes, one 66 times our sun’s mass and the other 85 times our sun’s mass, crashing together. Combined they created a black hole that was 142 times our sun’s mass. Previously observed stellar black hole mergers never resulted in any this big.
The collision released a gravitational wave, a space ripple that moves at the speed of light — this was the signal the astronomers heard. Yes, heard. The detectors called LIGO and Virgo turn gravitational waves into audio signals. The “thud” lasted one-tenth of a second.
But here’s the real kicker. The crash is so distant from Earth it happed 7 billion years ago and astronomers could only detect it now.
“We have the great breakthrough today where we’re looking towards the future already with future detectors that will tell us even more about the universe,” Christensen told the Associated Press. “And I just find that incredible to think that we’ve discovered so much but we’re also working hard to continue this with even more in the future.”
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