Comet West

C/1975 V1 (West)

Comet West on March 9, 1976
Discovery
Discovered by	Richard M. West
Discovery date	August 10, 1975
Alternative designations	C/1975 V1, 1976 VI, 1975n
Orbital characteristics A
Epoch	1976-Mar-03 (JD 2442840.5)
Aphelion	up to 70,000 AU (1.1 light-years)
Perihelion	0.197 AU
Eccentricity	0.99997 (near parabolic)
Orbital period	chaotic (more than 250 thousand years and maybe millions of years)
Inclination	43.0664°
Last perihelion	February 25, 1976
Next perihelion	unknown

Comet West, formally designated C/1975 V1, 1976 VI, and 1975n, was a comet which became one of the brightest objects in the night sky as it passed through the inner solar system in 1976. It is often described as a "great comet".

It was discovered photographically by Richard M. West, of the European Southern Observatory, on August 10, 1975. The comet came to perihelion (closest approach to the Sun) on February 25, 1976. During perihelion the comet had a minimum solar elongation of 6.4° and as a result of forward scattering reached a peak apparent magnitude of -3. From February 25 through the 27th, observers reported that the comet was bright enough to study during full daylight.

Despite its brightness, Comet West went largely unreported in the popular media. This was partly due to the relatively disappointing display of Comet Kohoutek in 1973, which had been widely predicted to become extremely prominent: scientists were wary of making predictions that might raise public expectations.

With a nearly parabolic trajectory, estimates for the orbital period of this comet have varied from 254,000 to 558,000 years, and even as high as 6.5 million years. Computing the best-fit orbit for this long-period comet is made more difficult since it underwent a splitting event which may have caused a non-gravitational perturbation of the orbit. The 2008 SAO Catalog of Cometary Orbits shows 195 observations for C/1975 V1 and 135 for C/1975 V1-A, for a combined total of 330 (218 observations were used in the fit). Comet C/1999 F1 has a similar period. Aphelion is estimated at 70,000 AU, but orbital periods of millions of years are very unstable as they are subject to perturbations by passing stars and the galactic tide.