LMC X-1
What is LMC X-1?
Black holes & quasars· Distance 160,000 ly. The first X-ray source found outside our galaxy and the first black hole confirmed in another galaxy. Inside the Large Magellanic Cloud it circles a hot 30-solar-mass giant every 3.9 days, feeding on the giant's stellar wind.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where LMC X-1 is in your sky right now: https://nowsky.org/solar/sky?sel=lmc x-1 — location and time set automatically, no login.
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 |
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.
Frequently asked
- What is the mass of LMC X-1?
- ~11 Suns.
- How far is LMC X-1 from Earth?
- ~160,000 ly (LMC).
- When was LMC X-1 discovered?
- 1969, first extragalactic X-ray source.
- Where in the sky is LMC X-1?
- In the direction of Mensa.
- Where is LMC X-1 in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
A black hole spinning at 92 percent of light speed — the 2009 measurement
A 2009 analysis of LMC X-1's X-ray spectrum gave the black hole's spin parameter as 0.92 — fast rotation, close to the maximum of 1. The method fits the thermal spectrum of the accretion disk, using the fact that how close the disk's inner edge reaches to the black hole depends on the spin. The mass (11 Suns), distance and inclination must first be fixed from the companion's orbit, and LMC X-1 was one of the rare systems in which all three were well measured.
Whether the spin dates from birth or was gained by swallowing the companion's gas is hard to separate. LMC X-1's companion is a hot star of 30 solar masses, so the system is young, about five million years old, and the spin that could be acquired by accretion in that time is small. The black hole is therefore read as having been born spinning fast — a specimen of how much angular momentum survives when a massive star's core collapses.
The black hole in depth
LMC X-1 was picked up in a 1969 rocket-borne X-ray survey toward the Large Magellanic Cloud, the first X-ray source found outside the Milky Way. Inside that galaxy, about 160,000 light-years away, a black hole of roughly 11 solar masses and an O-type giant of about 30 Suns orbit each other every 3.9 days. The companion is so massive and hot that, as in Cygnus X-1, the black hole feeds on its powerful stellar wind and glows in X-rays.
In 1983 radial-velocity measurements of the companion showed the unseen object exceeded the neutron-star limit, making it the first black hole confirmed in another galaxy. Precise work in 2009 fixed its mass and orbit, and X-ray spectra indicate the black hole spins at about 92 percent of the maximum rate. Because the LMC's distance is well known, its luminosity and mass are actually better constrained than those of many black holes in our own galaxy.
The companion star is fourteenth magnitude, reachable with medium telescopes from the southern hemisphere, but the Large Magellanic Cloud never rises from Korea. Select LMC X-1 in the Sky view to see its position inside the LMC in Dorado near the Tarantula Nebula, and switch the observing site to a southern city to watch it climb into the sky.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.