How Many Black Holes Are in the Milky Way?
The short answer
Maybe 100 million. That's the estimate NASA and ESA/Hubble give for our galaxy. But only about two dozen have been confirmed. On its own, a black hole gives off no light, so we only find the ones doing something to the things around them.
The biggest is Sagittarius A*, at the center of the Milky Way. It's about 4 million times the mass of the Sun. The film's scoreboard leaves it out and counts only the much smaller ones.
Three ways to catch something dark
Watch it eat. Most black holes we know have a partner star. The black hole pulls gas off the star, and the gas heats up until it glows in X rays. That's Kevin and his glowing crumbs. In the film, this trap catches about 20.
Watch a star dance. Sometimes a star circles a spot where nothing shows. Something heavy and dark has to be there. The Gaia space telescope has found black holes this way. In the film, they're Doug, Steve and Barb.
Watch the light bend. A lone black hole has no partner to give it away. But its gravity bends light. When one drifts in front of a distant star, the star looks brighter for a while and shifts a tiny bit. Telescopes on the ground caught one event like this, and Hubble measured the shift to weigh the object. It sits about 5,000 light years away. It's still the only lone black hole ever confirmed.
Most of them are loners
Lone black holes are probably the most common kind. Two simulations of the galaxy agree. Olejak and colleagues (2020) get about 120 million single black holes and about 9 million in pairs. Wagg and colleagues (2026) find that about 91% are on their own today. That's where the film's 9 in 10 comes from.
So nearly all of the two dozen we know are the unusual kind: black holes with company. The common kind, alone and dark, almost never shows up.
Why counting takes so long
The owl in the film plans to be done by lunch. The film's answer: at the pace we've found them so far, it would take something like 200 million years.
Here's another way to picture 100 million. Fill stadiums that hold 100,000 each with black holes, and you need about 1,000 stadiums.
Key numbers
| What | Number | Source |
|---|---|---|
| Black holes in the Milky Way (estimate) | maybe 100 million | NASA, Black Hole Types |
| Mass of Sagittarius A*, at the center of the galaxy | about 4 million times the mass of the Sun | NASA, Black Hole Types |
| Lone black holes ever confirmed | 1 | Sahu et al. 2025 |
| Distance to that lone black hole | about 5,000 light years | ESA/Hubble heic2210, 2022 |
| Its speed when it crossed in front of a star | about 160,000 km/h | ESA/Hubble heic2210, 2022 |
| Share of black holes on their own today | about 91% | Wagg et al. 2026 |
| Single black holes against black holes in pairs | about 120 million single, about 9 million in pairs | Olejak et al. 2020 |
| Stadiums of 100,000 needed to seat 100 million black holes | about 1,000 | Our arithmetic from NASA, Black Hole Types |
What the film simplifies
- The film's scoreboard stops at 24 and leaves out Sagittarius A*, the giant at the center of the galaxy. It counts only the much smaller black holes.
- 100 million is an estimate, not a count. That's why the film says 'maybe'.
- 'About 9 in 10' rounds two simulations: about 91% alone in one, and about 120 million single against about 9 million in pairs in the other.
- The 200 million years is a rough joke about how slowly we find them, not a forecast.
- Black holes don't wear sneakers, eat snacks or have cousins, and stars don't waltz. The faces, the crumbs, the light dots and the stadiums are drawn as cartoon.
At a glance
Runtime 1 minute 3 seconds · Topics: Black holes, The Milky Way, Gravity bending light · Captions on YouTube · Full script below
Test yourself
There may be 100 million black holes in the Milky Way. Why have we confirmed only about two dozen?
Answer
On its own, a black hole gives off no light. We only see the ones that do something to their surroundings: pulling glowing gas off a partner star, making a star circle an empty spot, or bending a distant star's light.
A stadium holds 100,000 people. How many stadiums would you need to seat 100 million black holes?
Answer
About 1,000, because 100 million divided by 100,000 is 1,000.
Most black holes we've found have a partner star, yet about 9 in 10 black holes are alone. How can both be true?
Answer
A partner star gives a black hole away, so those are the ones we find. A lone one only shows up when it happens to pass in front of a distant star, and that has led to only one confirmed loner so far.
The script
Lone Black Hole: Bet you can't find me!
The Owl: I'll count every black hole in our galaxy.
Lone Black Hole: There's maybe 100 million of us, bird!
The Owl: Easy. Done by lunch.
Host: At our pace so far? Something like 200 million years.
The Owl: ...Late lunch.
Host: On its own, a black hole gives off no light.
Lone Black Hole: Zero light. I'm a professional.
The Owl: Trap one. Follow the crumbs.
Kevin: Ooh. Snack!
Host: Messy eater. His crumbs glow at millions of degrees.
The Owl: Gotcha. About 20 of you!
Lone Black Hole: Kevin! I said no snacks.
Lone Black Hole: Doug, Steve, Barb! No dancing!
The Owl: Stars don't waltz alone. 23!
Lone Black Hole: Amateurs. I fly solo.
Host: Maybe a thousand stadiums of black holes. The owl knows nobody here.
Lone Black Hole: Psst. My cousin's probably closer than most stars you can see.
The Owl: Then I'll just watch a star.
Lone Black Hole: Zero light!
The Owl: Your gravity bent its light! 24!
Host: That's how we caught our only known loner, far away.
Lone Black Hole: I'm one of a kind!
Host: About 9 in 10 black holes are loners.
Sources
- Maybe 100 million black holes in the Milky Way; Sagittarius A* is about 4 million times the mass of the Sun; in pairs, the black hole pulls gas off its star and the gas heats up enough to glow in X rays.NASA, Black Hole Types
- Astronomers estimate 100 million black holes in the Milky Way. The lone black hole found when its gravity brightened a distant star and shifted its image: about 5,000 light years away, spotted by ground telescopes, weighed by measuring the shift with Hubble, moving at about 160,000 km/h.ESA/Hubble heic2210, 2022
- OGLE 2011 BLG 0462 is the first and only isolated black hole confirmed so far (as of 2025).Sahu et al. 2025
- About 91% of Milky Way black holes are currently isolated.Wagg et al. 2026
- About 120 million single black holes against about 9 million in binaries in the Milky Way.Olejak et al. 2020