LMC X-1
What is LMC X-1?
Black holes & quasars· Distance 160,000 ly. The first X-ray source found in the Large Magellanic Cloud and one of the earliest black holes identified in another galaxy. A black hole of about 11 Suns and a hot star of about 30 Suns circle each other every 3.9 days, and the black hole swallows gas blown off the star.
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Its place in the sky
A black hole, in the direction of Mensa.
Mass, distance, nature
| Mass | ~11 Suns |
|---|---|
| Distance | ~160,000 ly (LMC) |
| Companion | O-type giant of 30 Suns, 3.9-day orbit |
| Size | event-horizon radius ~32 km |
| Discovered | 1969, first extragalactic X-ray source |
| How the mass is measured | the companion star’s Doppler-measured orbit, its tilt and the companion’s mass |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
An X-ray source found in 1969 — the first black hole confirmed outside our galaxy.
How fast LMC X-1's black hole spins
A 2009 study of LMC X-1's X-rays found that the black hole spins at about 92 percent of the fastest rate theory allows. The faster a black hole spins, the closer its gas disk can come to it, and the hotter the inner disk becomes. So the shape of the X-ray light from the disk shows roughly how fast the black hole is turning.
The calculation needs the black hole's mass, its distance and the tilt of the disk to be known first, and LMC X-1 was a rare system where all three were well measured. Because the companion is so massive, the pair is young, only a few million years old. In so short a time the black hole could hardly have been spun up this much by swallowing gas, so scientists think it was born spinning fast.
The black hole in depth
LMC X-1 was found in 1969 in data from a rocket flight, the first X-ray source discovered in the Large Magellanic Cloud. The LMC is a small galaxy that orbits the Milky Way, about 160,000 light-years away. Inside it, a black hole of about 11 solar masses and a hot star of about 30 solar masses circle each other every 3.9 days — a very tight pair compared with Earth's one-year orbit.
The companion is so heavy and hot that it blows gas off its surface in a strong wind. The black hole pulls in and swallows this gas, which heats up as it falls and gives off X-rays. In the 1980s measurements of the companion's motion showed that the unseen partner was too heavy to be a neutron star. Because the distance to the LMC is well known, the brightness and mass of this system are fairly easy to work out.
The companion is about 14th magnitude, visible in medium-sized telescopes from the southern hemisphere, but the Large Magellanic Cloud never rises from Europe or the continental United States. In the Sky view it appears inside the LMC in Dorado, near the Tarantula Nebula, and switching the observing site to a southern city shows it up in the sky.
Frequently asked
- What is the mass of LMC X-1?
- The mass of LMC X-1 is ~11 Suns.
- How far is LMC X-1 from Earth?
- The distance of LMC X-1 is ~160,000 ly (LMC).
- When was LMC X-1 discovered?
- LMC X-1 was discovered in 1969, first extragalactic X-ray source.
- Where in the sky is LMC X-1?
- LMC X-1 lies in the direction of Mensa.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.