Cygnus X-3 is a high-mass X-ray binary (HMXB), one of the stronger binary X-ray sources in the sky. It is often considered to be a microquasar, and it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion. It is one of only two known HMXBs containing a Wolf-Rayet star. It is invisible visually, but can be observed at radio, infrared, X-ray, and gamma-ray wavelengths. Observations Cygnus X-3 is a prominent X-ray source, with soft and hard X-rays both varying in intensity. Periods where the hard X-rays are at minimum intensity are known as soft states. It is less than half a degree from a gamma-ray pulsar, but is itself a weak gamma-ray source. It also shows periodic gamma-ray flares, apparently all occurring during the soft state. It is undetectable at visual wavelengths due to extreme extinction in the galactic plane. However, there is an infrared point source at its position. Cygnus X-3 is also notable as the only microquasar firmly detected in the high energy gamma rays in the range >100 MeV. Because of the variations in emission at various wavelengths, Cygnus X-3 has been given the variable star designation V1521 Cygni. Flares Cygnus X-3 is notable for its intense X-ray emission, but it is also remarkable for its gamma-ray and radio flares during which it becomes the brightest radio source in the Milky Way. The gamma-ray flares apparently occur in the quiet radio period before a major radio flare. During the giant radio flares, a relativistic jet has been resolved within about of being aimed directly towards us. Binary system Cygnus X-3 shows consistent variations across all wavelengths with a period. The nature of the infrared spectrum and the x-ray emission is interpreted as a binary system containing a Wolf-Rayet (WR) star and a compact object. The variations have been interpreted as eclipses, but this is thought to be unlikely because there are not well-defined periodic dips in the brightness. The orbit of the binary system is not known accurately, other than the period. Therefore, the masses of the components are not known accurately. Orbital analysis suggested that the mass of the compact object is less than , probably around . It could possibly be a neutron star but is more likely to be a black hole. The combination of a WR star and