Where Is the Closest Black Hole to Earth?
The short answer
The closest black hole we know of is Gaia BH1. It is about 1,600 light years away, in the constellation Ophiuchus, and has about 10 times the mass of the Sun. It is dormant: astronomers have detected no X rays or radio from it.
Driving there at 96.6 km/h (60 mph) would take about 17 billion years. And it can't hurt you. From that far away, a house cat across the room pulls on you millions of times harder.
How do you find something invisible?
You watch what it pulls on. The Gaia space telescope measured the positions of nearly two billion stars, over and over. Its third data release alone holds 1.81 billion sources from 34 months of watching.
A star on its own drifts across the sky in a straight line. One star, almost a twin of our Sun, also traced a loop every 185.6 days around a spot where nothing shows. Gaia's measurements showed the loop, and telescopes on the ground checked and sharpened it. The size and speed of the loop give the hidden partner's mass: 9.62 Suns in the 2023 discovery paper, and 9.27 in a sharper 2024 study. That much mass with no light of its own points to a black hole.
The star has 0.93 times the Sun's mass and a surface at 5,850 K, give or take 50 K. On average her orbit is 1.40 times Earth's distance from the Sun. It is an oval, so at her closest she swings in to about 0.77 times Earth's distance. NOIRLab's release quotes the discovery team: "Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is."
Why your cat wins
Gravity weakens with the square of distance. Twice as far, a quarter of the pull. Ten times as far, a hundredth.
Gaia BH1 is heavy, but it is 480 parsecs away, about 1,560 light years. Put a 4 kg cat 3 m from you and do the math: the cat pulls on you about 5.1 million times harder than the black hole does. At 1 m, it's about 46 million times.
The giant black hole at the center of our galaxy, Sagittarius A*, has about 4 million times the Sun's mass. But it is about 27,000 light years away. A 4 kg cat anywhere within about 175 m of you pulls harder than Sagittarius A* does. That's a few houses down the street.
Key numbers
| What | Number | Source |
|---|---|---|
| Distance to Gaia BH1 | 480 parsecs, about 1,560 light years (the film rounds to 1,600) | El-Badry et al. 2023 |
| Mass of Gaia BH1, discovery paper | 9.62 ± 0.18 times the Sun | El-Badry et al. 2023 |
| Mass of Gaia BH1, refined | 9.27 ± 0.10 times the Sun | Nagarajan et al. 2024 |
| Time for the star to go once around the black hole | 185.6 days | El-Badry et al. 2023 |
| Average size of the star's orbit | 1.40 times Earth's distance from the Sun (1.40 AU), eccentricity 0.45 | El-Badry et al. 2023 |
| The star's closest approach to the black hole | about 0.77 AU, inside the size of Earth's orbit | Our arithmetic from El-Badry et al. 2023 |
| The star itself | 0.93 times the Sun's mass, surface 5,850 ± 50 K | El-Badry et al. 2023 |
| Stars Gaia measured | nearly two billion | ESA, Farewell Gaia, 2025 |
| Driving time to Gaia BH1 at 96.6 km/h (60 mph) | about 17.4 billion years | Our arithmetic from El-Badry et al. 2023 |
| Pull of a 4 kg cat 3 m away, compared with Gaia BH1's pull | about 5.1 million times stronger | Our arithmetic from El-Badry et al. 2023 |
| Sagittarius A*, the black hole at the center of our galaxy | about 4 million times the Sun's mass, about 27,000 light years away | ESO, eso2208, 2022 |
| Distance within which a 4 kg cat out pulls Sagittarius A* | about 175 m | Our arithmetic from GRAVITY Collaboration 2019 and GRAVITY Collaboration 2022 |
What the film simplifies
- The film rounds the distance to about 1,600 light years and the drive to about 17 billion years. The paper's 480 parsecs is about 1,560 light years, which takes about 17.4 billion years at 96.6 km/h (60 mph). A full 1,600 light years would take nearer 18 billion.
- Gaia doesn't take flash photos. It measures where each star sits, again and again, and telescopes on the ground checked and sharpened the orbit it found. The flash, the black hole's eye and the star's face are cartoon.
- As Gaia sees them, single stars don't drift perfectly straight. Every star also traces a small yearly loop because Earth moves around the Sun. The black hole's pull adds a second loop on top of that.
- "Her orbit's a bit bigger than Earth's" describes the average, 1.40 times Earth's distance. The orbit is an oval, and at its closest it comes in to about 0.77 times Earth's distance.
- "It isn't eating, so it doesn't glow" is the film's shorthand. What astronomers measured is that no X rays or radio could be detected from it. That is why it's called dormant. The glowing disk in the cat's thought bubble shows what it isn't doing.
- "A little hotter" is the best estimate: her 5,850 K, give or take 50 K, against the Sun's 5,772 K. The 78 K gap is only about 1.6 times that margin, so the two may be even closer than the film suggests.
At a glance
Runtime 1 minute 14 seconds · Topics: Black holes, Gravity, Gaia space telescope · Captions on YouTube · Full script below
Test yourself
Gaia BH1 gives off no light we can detect. How did astronomers find it?
Answer
Gaia saw a star much like our Sun loop around an empty spot every 185.6 days. A star on its own drifts in a straight line, so the loop meant something about 10 times the Sun's mass was pulling on it.
Gravity falls with the square of distance. If a cat moves from 1 m to 2 m away from you, how does its pull on you change? What about from 1 m to 3 m?
Answer
At 2 m it pulls a quarter as hard, and at 3 m a ninth as hard. That's why the cat's lead over Gaia BH1 drops from about 46 million times at 1 m to about 5.1 million times at 3 m.
Why does the film say "the closest black hole we know of" and not just "the closest black hole"?
Answer
A dormant black hole gives off no light we can detect, and Gaia BH1 was found only through its pull on a companion star. A closer one could exist that nobody has spotted yet.
The script
Host: Your cat pulls on you harder than the closest black hole to Earth.
Host: It's about sixteen hundred light years that way.
Host: Driving? About seventeen billion years. The universe isn't that old.
Host: You get there. Nothing. It isn't eating, so it doesn't glow.
Host: How do you find something invisible? Watch what it pulls on.
Host: A space telescope called Gaia photographed nearly two billion stars.
Host: One star kept looping around... nothing.
The Star: Nobody here! I'm single! Totally, completely single!
Host: Single stars drift straight. A loop means something's pulling.
Host: Something about ten times heavier than the Sun. The closest black hole we know of.
The Star: Okay, fine! He just doesn't do photos.
Host: And she's nearly our Sun's twin.
The Star: Nearly? I'm a little hotter. Look it up.
Host: Anyway. Her orbit's a bit bigger than Earth's.
Host: It's our solar system, with a black hole where the Sun goes.
Host: Gravity fades fast with distance. Twice as far, a quarter of the pull.
Host: Your cat has gravity too. He's just about sixteen hundred light years closer.
Host: So he pulls on you millions of times harder.
The Star: What about the giant black hole in the middle of the galaxy?
Host: Your neighbor's cat, a few houses down, still wins.
Host: That's why your cat looks at you like that.
Sources
- Gaia BH1 is the nearest known black hole by a factor of 3; distance 480 pc; mass 9.62 ± 0.18 Suns; orbital period 185.6 days; eccentricity 0.45; semi major axis 1.40 AU; the star is a G dwarf of 0.93 Suns, radius 0.99, Teff 5,850 ± 50 K, in Ophiuchus.El-Badry et al. 2023
- Gaia BH1 is about 1,600 light years away in Ophiuchus and dormant; "Take the Solar System, put a black hole where the Sun is, and the Sun where the Earth is".NOIRLab 2022
- Refined black hole mass 9.27 ± 0.10 Suns, using Gaia's inclination.Nagarajan et al. 2024
- No X rays or radio detected from the nearest black holes: "We did not detect either system".Rodriguez et al. 2024
- Gaia mapped the positions, distances and motions of nearly two billion stars.ESA, Farewell Gaia, 2025
- Gaia DR3 holds 1.81 billion sources from 34 months of data.ESA, Gaia Data Release 3, 2022
- Gravity follows the inverse square law.HyperPhysics, Georgia State University
- Sagittarius A* is about four million times the Sun's mass and about 27,000 light years from Earth.ESO, eso2208, 2022
- Distance to the Galactic Center R0 = 8,178 pc.GRAVITY Collaboration 2019
- Mass of Sagittarius A* 4.30 million Suns.GRAVITY Collaboration 2022