C/1975 V1 (West)

Observational history

It was discovered photographically by Richard M. West, of the European Southern Observatory, on 10 August 1975. The comet came to perihelion (closest approach to the Sun) on 25 February 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 25 to 27 February, 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.

The New York Times, however, reported this about Comet West on 2 March 1976:

From tomorrow until Sunday a comet that may prove one of the brightest in this decade is expected to reach maximum visibility in the eastern sky before sunrise. ... By Wednesday, Dr. Marsden believes, it will be far enough from the sun to be visible to the unaided eye

— Walter Sullivan, The New York Times (2 March 1976)

Breakup

Before the perihelion passage, and using 28 positions obtained between 10 August 1975 and 27 January 1976, Comet West was estimated to have an orbital period of about 254,000 years. As the comet passed within 30 million km of the Sun, the nucleus was observed to split into four fragments.

The first report of the split came around 7 March 1976 at 12:30 UTC, when reports were received that the comet had broken into two pieces. Astronomer Steven O'Meara, using the 9-inch Harvard Refractor, reported that two additional fragments had formed on the morning of 18 March.

The fragmentation of the nucleus was, at the time, one of very few comet breakups observed, one of the most notable previous examples being the Great Comet of 1882, a member of the Kreutz Sungrazing 'family' of comets. More recently, comets Schwassmann–Wachmann-3 (73P), C/1999 S4 LINEAR, and 57P/du Toit-Neujmin-Delporte, have been observed to split or disintegrate during their passage close to the Sun.