Crab Nebula
What is Crab Nebula?
Nebulae· Distance 6,500 ly. The debris of a supernova seen in daylight in AD 1054, still expanding at 1,500 km/s around a pulsar that spins 30 times a second. Find it near the tip of the Bull's southern horn in the Sky view.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Crab Nebula is in your sky right now: https://nowsky.org/solar/sky?sel=crab nebula — location and time set automatically, no login.
Its place in the sky
A pulsar, in the direction of Taurus, spanning about 6 arcminutes of sky — 0.2 times the width of the full Moon.
Distance and scale
| Distance | 6,500 ly |
|---|---|
| Size | ~11 ly across |
| Type | supernova remnant + pulsar |
| Constellation | Taurus |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
Remains of the "guest star" of 1054 recorded in China and Arabia; Messier mistook it for a comet and made it his No. 1.
Frequently asked
- How far is Crab Nebula from Earth?
- 6,500 ly.
- What kind of object is Crab Nebula?
- supernova remnant + pulsar.
- Where in the sky is Crab Nebula?
- In the direction of Taurus.
- Where is Crab Nebula in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The name "Crab" — Lord Rosse's sketch
M1 became the Crab Nebula in 1844, when Lord Rosse in Ireland sketched what he saw through his 91 cm telescope. Filaments spreading in all directions looked like a crab's legs and the name stuck, though a few years later, viewing it with a larger telescope, he redrew it and admitted the shape was different. The name stayed with the first sketch, and the nebula in modern photographs resembles an exploding firework more than a crab.
Name aside, the Crab is among the most studied objects in astronomy. It was tied to the supernova of 1054 in 1921, when the nebula was found to be expanding and running the expansion backward gathered it to a point nine centuries earlier. The whole nebula shines on the energy of its central pulsar, and its X-ray brightness is so steady that it serves as the calibration standard for X-ray telescopes — which is why astronomers quote X-ray brightness in "crabs".
The nebula in depth
The Crab Nebula is the first entry in Messier's catalogue, M1. In July 1054 Chinese, Japanese and Arab records noted a "guest star" that stayed visible in daylight for 23 days and lingered in the night sky for nearly two years. Where that star exploded now lies an irregular cloud of gas about 11 light-years across, its filaments resembling the legs of a crab.
At its heart sits the Crab Pulsar, found in 1968: a neutron star barely 20 km wide that spins 30 times per second and flashes across radio, visible, X-ray and gamma-ray wavelengths. Its rotational energy powers the whole nebula like a dynamo, and the gas is still expanding at about 1,500 km/s. The Crab is so steady that astronomers use it as a standard candle for X-ray brightness.
In the Sky view, look just beside Zeta Tauri, the star at the tip of the Bull's southern horn. It rides high in the winter evening sky. At 8th magnitude it is invisible to the naked eye, a faint smudge in binoculars and an oval glow in a small telescope. Compare it with the solar system on the size ladder to appreciate how vast this remnant is.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.