“There are only about five dozen known black holes in the entire galaxy—120,000 light years wide—and there are supposed to be 10,000 to 20,000 of these things in a region just six light years wide that no one has been able to find,” said Columbia University astrophysicist Chuck Hailey, co-director of the Columbia Astrophysics Lab, adding that extensive fruitless searches have been made for black holes around Sgr A*, the closest SMBH to Earth and therefore the easiest to study. “There hasn’t been much credible evidence.”
“It is possible that there’s a zoo of different compact objects, and while some of them are the black holes that follow Einstein and Hawking’s laws, others may be slightly different beasts,” says Maximiliano Isi, a NASA Einstein Postdoctoral Fellow in MIT’s Kavli Institute for Astrophysics and Space Research and lead author of a study about a signal from a gravitational wave merger.
While the billion-dollar Laser Interferometer Gravitational-Wave Observatory (LIGO) detector watches 24/7 for gravitational waves to pass through the Earth, new research shows those waves leave behind “memories” –a permanent displacement of spacetime that comes from strong-field, general relativistic effects–that could help detect them even after they’ve passed, creating the potential to tell us about everything from the time following the Big Bang and the creation of cosmic strings–to more recent events in galaxy centers.
This week’s newsletter covers news reports from “Why aren’t we talking more about UFOs?” asks Megan McArdle in the Washington Post to the first matter in the universe may have been a perfect liquid to the Milky Way’s supermassive black hole, Sagittarius A*, may actually be a colossal glob of dark matter.
“According to Einstein’s Theory of General Relativity, nothing can escape from the gravity of a black hole once it has passed a point of no return, known as the event horizon,” explained Niayesh Afshordi, a physics and astronomy professor at Waterloo in 2020 about echoes in gravitational wave signals that hint that the event horizon of a black hole may be more complicated than scientists currently think. Afshordi’s conjecture is based on research reporting the first tentative detection of these echoes, caused by a microscopic quantum “fuzz” that surrounds newly formed black holes.
New research suggests that in massive galaxies, the central black hole –a strange galactic monster, for which creation is destruction, death is life, and chaos is order – is like a parasite that ultimately grows and kills off star formation. Although many theories have been proposed to explain this process, known as “quenching,” a new study concludes that the growth rate of black holes must change as galaxies evolve from one stage to the next., Suggesting that most of the black hole growth occurs in the “green valley” when galaxies are beginning to quench.