Black holes should be common in our Milky Way galaxy, but their dark nature means only dozens have been discovered to date. Here are a few nearby black holes astronomers know a little about.
By nature, it is impossible to see black holes directly. But astronomers can sense their presence by the way they interact with their environments, letting us glimpse these objects whose gravity is so strong that nothing can escape. In the past century, not only have astronomers shown that black holes do exist, but they’ve found dozens in our own galaxy.
However, based on the number of stars in our galaxy, there should actually be tens of millions out there. Let us now see the top 10 black holes which are closest to our Earth.
1. A0620-00, or V616 Monocerotis:
This black hole occassionally releases dramatic outbursts of X-Ray light. One of these happened in 1917 and that is how it was discovered. During the outburst in 1975 this black hole brightened over 1,00,000 times becoming the brightest X-Ray source at that time. Some of the details of this black hole are given below
- It is about 3,500 light-years away
- 6.6 solar masses
- Paired with a K-type main sequence star orbiting every 7.75 hours — less than the average work day
- Its companion star is only around 40 percent of our sun’s mass. And the star is continually losing mass to the black hole, whose pull is so strong it’s squeezed into an ellipsoid instead of a sphere.
2. Cygnus X-1:
It is suspected by scientists that this black hole Cygnus X-1 began its life as a star 40 times the mass of our Sun. It is likely collapsed directly to form a black hole some 5 million years ago. Some details of this black hole are given below.
- 6,000 light-years away
- 14.8 solar masses
- The black hole has an event horizon 185 miles across — about the length of New Hampshire.
- Cygnus X-1’s companion star is a blue supergiant variable star that orbits every 5.6 days at just one-fifth of the sun-Earth distance.
3. V404 Cygni:
Scientists reported a wobble in giant jets of particles shot out by the black hole in V404 Cygni in 2019. They think this wobble could be caused by a black hole warping space-time. Some details of this black hole are given below.
- 7,800 light-years away
- 9 solar masses
- Paired with an early K giant star that’s 70 percent as massive as our own sun, but six times larger in diameter.
4. GRO J0422+32:
This black hole is either the smallest ever found that formed from the collapse of star, or it could be a neutron star — the verdict is still out. Some details of this black hole are
- 7,800 light-years away
- 3.66 to 5 solar masses
- Companion to an M-type main sequence star named V518 Per
5. Cygnus X-3:
The mass of this black hole is not well measured and the scientists are uncertain if Cygnus X-3 actually holds a black hole or a neutron star. The object is paired with a Wolf-Rayet star — an incredibly bright object with an unusual distribution of elements, particularly on its surface — that is one of the brightest stars in the galaxy. The star will likely become a black hole itself fairly soon, so stay tuned — for the next million years or so. Some details of this black hole are
- 20,00 light-years away
- Roughly 2 to 5 solar masses
6. GRO J1655-40:
This black hole and star are traveling through the galaxy at 250,000 mph. For comparison, the sun cruises at only 44,740 mph. Astronomers think they achieved their breakneck pace when the black hole was created by an asymmetric supernova, which gave the system a kick. Some details of this black hole are
- 11,000 light-years away (perhaps much closer)
- 7 solar masses
- Paired with an evolved F-type star that’s two times as massive as our sun.
- The star and black hole are locked in an orbit every 2.6 days.
- The black hole spins 450 times per second — fast enough to warp the space around it.
7. Sagittarius A*:
Sagittarius A* (pronounced A-star) is the Milky Way’s central supermassive black hole. It was first noticed in 1931, thanks to a radio signal coming from the center of the galaxy. But by observing the motions of nearby stars over decades, and watching clumps of gas near the object, astronomers have since firmly determined that it is indeed a supermassive black hole. What’s more, they now know most large galaxies also have them. Some details of this black hole are
- 25,640 light-years away
- More than 4 million solar masses
8. 47 Tuc X9:
Scientists are still debating whether there’s actually a black hole in the globular cluster 47 Tucanae. Recent studies offer evidence for and against the idea. But, if it is there, it would be a rare example of a black hole in a globular cluster — something astronomers long thought was impossible. It would also have the closest orbit ever seen between a black hole and a star. Some details of this black hole are
- 14,800 light-years away
- Mass unknown
- Every 28 minutes, the black hole orbits its companion white dwarf star at a separation of just 2.5 times the distance between Earth and the moon.
9. XTE J1118+480:
Some details of this black hole are as follows.
- 5,000 to 11,000 light-years away
- More than 6 solar masses
- Paired with a star that packs just 20 percent of the sun’s mass
- Suspected to have been formed by a metal-rich star that underwent a supernova
10. GS2000+25:
- 8,800 light-years away
- 7 solar masses
- Paired with a late K-type star with 50 percent of the sun’s mass
- Binary pair orbits every 8.26 hours
