Crab Pulsar

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**Crab Pulsar**
Observation data Epoch J2000
The Crab Pulsar. Image combines optical data from Hubble (in red) and X-ray images from Chandra (in blue).
Constellation (pronunciation)	Taurus
Right ascension	05h 34m 31.97s
Declination	+22° 00' 52.1"'
Apparent magnitude (V)	16.5
Characteristics
Spectral type	F
U-B color index	-0.45
B-V color index	+0.5
Variable type	None
Astrometry
Radial velocity (R_v)	0.0 km/s
Proper motion (μ)	RA: 0.0 mas/yr Dec.: 0.0 mas/yr
Parallax (π)	7.0 ± 10.0 mas
Distance	6500 ly (2000 pc)
Absolute magnitude (M_V)	?
Details
Mass	? M_☉
Radius	? R_☉
Luminosity	? L_☉
Temperature	? K
Metallicity	?
Rotation	?
Age	? years
Other designations
SNR G184.6-05.8, PULS NP 0531, 3A 0531+219, NAME CRABE, AJG 1, 1ES 0532+21.5, NAME CRAB NEBULA, 2C 481, GeV J0534+2159, NAME CRAB SN, SN 1054, 3C 144.0, GRS 184.60 -05.80, NAME CRAB NEB SN 1054A, 3C 144, NAME CRAB PSR, 2U 0531+22, 4C 21.19, H 0531+219, NGC 1952, 3U 0531+21, 1CG 185-05, NOVA Tau 1054, 4U 0531+21, V* CM Tau, NRL 2, VRO 21.05.01, PKS 0531+219, W 9, CTA 36, LBN 184.62-05.65, PLX 1266, X Tau XR-1, CTB 18, LBN 833, PSR 0531, X Tau X-1, Cul 0531+219, PSR B0531+21, Cul 0531+21, Mills 05+2A, PSR 0532, DA 179, M 1, PSR B0532+21, NAME TAU A, PSR J0534+2200, NAME CRAB PULSAR, PSR B0531+21.9, NAME TAURUS A, PULS NP 0532.

A slow-motion movie of the Crab Pulsar taken at 800 nm wavelength using a Lucky Imaging camera from Cambridge University, showing the bright pulse and fainter interpulse.

The Crab Pulsar (PSR B0531+21 or PSR J0534+2200) is a relatively young neutron star located in the Crab Nebula, discovered in 1969. The optical pulsar is roughly 25 km in diameter and the pulsar "beams" rotate once every 33 milliseconds, or 30 times each second. The outflowing relativistic wind from the neutron star generates synchrotron emission, which produces the bulk of the emission from the nebula, seen from radio waves through to gamma rays. The most dynamic feature in the inner part of the nebula is the point where the pulsar's equatorial wind slams into the surrounding nebula, forming a termination shock. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar into the main body of the nebula. The period of the pulsar's rotation is slowing by 38 nanoseconds per day due to the large amounts of energy carried away in the pulsar wind.^[1]

The Crab Nebula is often used as a calibration source in X-ray astronomy. It is very bright in X-rays and the flux density and spectrum are known to be constant, with the exception of the pulsar itself. The pulsar provides a strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, 'crab' and 'millicrab' are sometimes used as units of flux density. A millicrab corresponds to a flux density of about 2.4x10^-11 erg s^-1 cm⁻² (2.4x10^-14 W m⁻²) in the 2–10 keV X-ray band, for a "crab-like" X-ray spectrum, which is roughly a powerlaw in photon energy, I(E)=9.5 E^-1.1. Very few X-ray sources ever exceed one crab in brightness.