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physical object > natural object > celestial body > X-ray source

X-ray source
subject			fact

X-ray source	has wavelength X-ray
	is a part of celestial sphere
	has definition A class of celestial objects whose dominant mechanism of energy dissipation is through X-ray emission. Galactic X-ray sources appear optically as starlike objects, peculiar in their ultraviolet intensity, variability (on time scales ranging from milliseconds to weeks), and spectral features. All known compact X-ray sources are members of close binary systems; a current popular model is mass accretion onto a compact object from a massive companion. (Four X-ray sources - all variable - are known to be associated with globular clusters.) The 21 known extended X-ray sources associated with clusters of galaxies seem to be clouds of hot gas trapped in the cluster's gravitational field.
	is a kind of celestial body
celestial body	has spectra
physical object	has location or center of gravity
	has angular momentum
	has mass
	has velocity
	has momentum
	has temperature
	has volume
	has extent
	has material

Kinds of X-ray source :

• Cassiopeia A (8 facts) (3C 461, 3U 2321+58) - A radio source in Cassiopeia, the strongest extrasolar source in the sky, believed to be the remnant of a Type II supernova whose light reached Earth about 1667. Optically it is a faint nebula. It has a mass of a few solar masses. It is also an extended source of soft X-rays.
• Cen X-4 (3 facts) - sporadic X-ray source
• Centaurus A (7 facts) (3U 1322-42, NGC 5128) - A strong radio source. Optically, it is an elliptical galaxy with a dark obscuring lane. It is the nearest known violent galaxy.
• Centaurus cluster (7 facts) (3U 1247-41) - A cluster of galaxies. Its radio counterpart is compact and located inside NGC 4696.
• Circinus X-1 (4 facts) (3U 1516-56) - A highly variable X-ray source. Many of its properties are similar to those of Cygnus X-1.
• Coma cluster (12 facts) (Coma X-1, Abell 1656) - The nearest massive cluster of galaxies. A symmetric cluster with primarily E and S0 galaxies. Luminous mass 4 × 10¹⁴ M_sun = 8 × 10⁴⁷ g; virial theorem mass about 5 × 10⁴⁸ g; mass needed to bind the cluster about 4 × 10⁴⁹ g. R ≈ 9 × 10²⁴ cm.
• Coma X-1 (5 facts) (3U 1257+28) - An extended X-ray source in the Coma cluster of galaxies.
• Cygnus A (5 facts) (3C 405, 2U 1957+40) - A double radio source, the third strongest radio source in the sky (after the Sun and Cas A), at one time believed to be caused by the collision of two galaxies. It has now been identified with a distant peculiar cD galaxy (z ≈ 0.056).
• Cygnus Loop (10 facts) (Veil Nebula, NG6 6992, Cygnus X-5) - A supernova remnant, consisting of a large loop of gas ejected from a star. It is 100 pc above the galactic plane. (X-ray observations give a distance of 2-3 kpc.) It is a thermal bremsstrahlung source of soft X-rays with a spectral temperature of 2 × 10⁶ K.
• Cygnus X-1 (11 facts) (3U 1956+35) - A black hole candidate in the constellation Cygnus and a source of X-rays., An X-ray source. The visible component is the ninth-magnitude supergiant HDE 226868 (O9.7 Iab). It has rapid night-to-night variations in spectral features.
• Cygnus X-2 (4 facts) (3U 2142+38) - An X-ray source optically identified with an irregular variable star.
• Cygnus X-3 (8 facts) (2U 2030+40) - An X-ray binary. It is also an infrared source, a cosmic ray source, and a strongly variable radio source (interstellar extinction is too high for visible light observations). It is best fitted by a model of an expanding cloud of relativistic electrons emitting synchrotron radiation around a neutron star.
• M 87 (12 facts) (3C 274, Virgo A, 2U 1228+12) - A strong radio source. Optically, it is an elliptical galaxy with a luminous blue jet about 1500 pc long. It is also one of the most powerful extragalactic sources of radiation at infrared wavelengths.
• NGC 1275 (11 facts) (3U 0316+41, Perseus X-1, Perseus A) - The strongest known extragalactic X-ray source. Also a strong radio source. Optically it is a Seyfert galaxy with a huge amount (about 10⁸ M_sun) of ionized gas receding from it.
• North Polar Spur (4 facts) - A radio continuum feature extending from the galactic plane to the vicinity of the North Galactic Pole. It is believed to be a supernova remnant. It is also an X-ray source.
• Puppis A (7 facts) (2U 0821-42) - A supernova remnant. It is an extended nonthermal radio source, and also a source of soft X-rays.
• Scorpius X-1 (7 facts) - A compact eclipsing X-ray source. It has day-to-day variations (period about 0.78 days?) of as much as 1 mag; it also has optical and radio counterparts but no correlation has been found among the flares observed at the three different wavelengths. It is a thermal X-ray source, probably associated with a rotating collapsed star surrounded by an extensive envelope. Tentative optical identification with the 13th mag blue variable V818 Sco. The spectrum of Sco X-1 is similar to that of an old nova. (3U 1617-15)
• transient X-ray source (4 kinds, 10 facts) - As of early 1974, four had been detected: Cen X-2, Cen X-1, 2U 1543-47, and Cep X-4. They resemble slow novae.
• Vela X-1 (11 facts) (HD 77581, 3U 0900-40)