The Milky Way galaxy contains some 100 billion stars. Roughly one out of every thousand stars that form is massive enough to become a black hole. Therefore, our galaxy must harbor some 100 million stellar-mass black holes. Most of these are invisible to us, and only about a dozen have been identified.
Most stellar black holes, however, are very difficult to detect. Judging from the number of stars large enough to produce such black holes, however, scientists estimate that there are as many as ten million to a billion such black holes in the Milky Way alone.
On 10 April 2019, the first direct image of a black hole and its vicinity was published, following observations made by the Event Horizon Telescope (EHT) in 2017 of the supermassive black hole in Messier 87's galactic centre.
Astronomers have discovered a black hole closer to Earth than any other previously found. It's about ten times as massive as our sun and is located just 1,600 light-years away—rather nearby on a cosmic scale.
Astronomers estimate that 100 million black holes roam among the stars in our Milky Way galaxy, but they have never conclusively identified an isolated black hole.
Wormholes are shortcuts in spacetime, popular with science fiction authors and movie directors. They've never been seen, but according to Einstein's general theory of relativity, they might exist.
Astronomers scanning through our Milky Way galaxy have made a remarkable and possibly rare discovery. Roughly 8,000 light years away is a binary star with the somewhat convoluted name "2MASS J05215658+4359220".
The 'missing' black hole
The black hole is supposed to be located in Abell 2261, an enormous galaxy cluster that is about 2.7 billion light-years away from our planet. One light-year is the distance that a beam of light travels in one Earth year, which is 9 trillion km.
Last year, scientists announced the discovery of J0313–1806, the most distant quasar on record at over 13 billion light-years from Earth, signifying the oldest supermassive black hole ever found.
There's no getting out. Even if you were still alive, you'd have to travel faster than the speed of light in order to escape. But as we know, nothing in the known universe can do that. But don't fret just yet; the closest known black hole to Earth is still a daunting 1,000 light-years away.
In pure general relativity, with no other modifications or considerations of other physics, they remain black for eternity. Once one forms, it will just hang out there, being a black hole, forever.
Just 1560 light-years away, this record is temporary. Gaia BH1, at ~10 solar masses, with an orbital period of ~180 days, and located just 1560 light-years away, now holds the record (as of 2022) for closest black hole known to our Solar System.
Black Holes, explained. These infinitely dense points in space will spaghettify anything that ventures too close. Black holes are points in space that are so dense they create deep gravity sinks. Beyond a certain region, not even light can escape the powerful tug of a black hole's gravity.
Well, even though black holes are extreme in many ways, they don't have infinite mass—and it's mass that determines the force of their gravity. Some black holes—known as stellar black holes. —have about the amount of mass that very massive stars do.
The largest black hole ever found in the known universe is found in Ton 618. This is a hyper luminous Lyman-alpha blob that has a black hole that measures 6.6×1010 solar masses. It has a mass that equals about 66 billion times that of the Sun. This supermassive black hole is some 18.2 billion light-years from Earth.
Astronomers have discovered the nearest known black hole to Earth, and it's twice as close as the previous record holder. The space-time singularity, named Gaia BH1, is 1,566 light-years away in the constellation Ophiuchus and is roughly 10 times more massive than our sun.
The remnant is located some 26,000 light-years from Earth and is just over a thousand years old (which is extremely young in cosmological terms). In fact, W49B is believed to be the youngest black hole that has been discovered in the Milky Way.
There is no theoretical upper limit to the mass of a black hole. However, astronomers have noted that the ultra-massive black holes (UMBHs) found in the cores of some galaxies never seem to exceed about 10 billion solar masses.
Because nothing can get out of black holes, physicists struggle understanding these objects. Not even the laws of physics tell us what happens when something falls into a black hole—at least not yet. Therefore, black holes remain cosmic mysteries, and many scientists work hard to solve the mystery of black holes.
Nothing escapes a black hole. Any trip into a black hole would be one way. The gravity is too strong and you could not go back in space and time to return home. Aside from this, your body would be stretched and destroyed by the warping of space and the amount of radiation surrounding the event horizon.
At the center of a black hole the gravity is so strong that, according to general relativity, space-time becomes so extremely curved that ultimately the curvature becomes infinite. This results in space-time having a jagged edge, beyond which physics no longer exists -- the singularity.
Despite their abundance, there is no reason to panic: black holes will not devour Earth nor the Universe. It is incredibly unlikely that Earth would ever fall into a black hole. This is because, at a distance, their gravitational pull is no more compelling than a star of the same mass.
There is no black hole near our Solar System, so there is no chance of Earth ever getting sucked into a black hole. In fact, the closest black hole to Earth is 1560 light years away from us. It would take us around 30 million years to travel there in a rocket!
Our Milky Way is on a collision course with another spiral galaxy called Andromeda. Today Andromeda is visible as a speck of light in the night sky, but about 5 billion years from now, it will be tangled up with us. Our galaxy's spiral arms will disappear, and so will our supermassive black hole.