Comet West

C/1975 V1 (West)
	Comet West on March 9, 1976
Discovery
Discovered by	Richard M. West
Discovery date	August 10, 1975
Designations
Alternative designations	C/1975 V1, 1976 VI, 1975n
Orbital characteristics
Epoch	1976-Mar-03; (JD 2442840.5)
Aphelion	1,500 AU (inbound)
Perihelion	0.197 AU
Eccentricity	0.99997 (near parabolic)
Orbital period	chaotic (estimates up to 558,000 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 described as one of the brightest objects to pass through the inner Solar System in 1976. It is often described as a "great comet."^[3]

History

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.^[1] 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.^[2] From February 25–27, observers reported that the comet was bright enough to study during full daylight.^[2]

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.^[4]

The New York Times, however, reported on March 2, 1976 that West was "a comet that may prove one of the brightest in this decade" and would be "visible to the unaided eye."^[5]

Period

With a nearly parabolic trajectory, estimates for the orbital period of this comet have varied from 254,000^[2] to 558,000 years.^[6] 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).

Breakup

Before the perihelion passage, and using 28 positions obtained between 1975 August 10 and 1976 January 27, Comet West was estimated to have an orbital period of about 254,000 years.^[2] As the comet passed within 30 million km of the Sun, the nucleus was observed to split into four fragments.^[7]

The first report of the split came around 7 March 1976 12:30UT, 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.^{[citation needed]}

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.^{[citation needed]}

The comet has been more than 50 AU (7.5 billion km) from the Sun since 2003.^[8]

Nomenclature

In the nomenclature of the time, it was known as Comet 1976 VI or Comet 1975n, but the modern nomenclature is C/1975 V1. (Note that "1976 VI" uses the Roman numeral VI = 6, while "C/1975 V1" is the letter V and the number 1).

References

^ ^a ^b ^c ^d ^e ^f "JPL Small-Body Database Browser: C/1975 V1-A (West)" (1976-09-25 last obs (arc=412 days)). Jet Propulsion Laboratory. Retrieved 2011-08-07.
^ ^a ^b ^c ^d ^e ^f Gary W. Kronk. "C/1975 V1 (West)". Cometography. Retrieved 2011-02-01.
^ Donald K. Yeomans (April 2007). "Great Comets in History". Jet Propulsion Laboratory/California Institute of Technology (Solar System Dynamics). Retrieved 2007-12-28.
^ Burnham, R. and Levy, D. Great Comets, Cambridge: Cambridge University Press, 2000, p. 73
^ Sullivan, Walter (March 2, 1976). "Comet Expected in Sky for Week". nytimes.com. New York City: New York Times. p. 17. Retrieved November 16, 2023. 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.
^ Jerry Coffey (2009-09-21). "Comet West". Universe Today. Archived from the original on 2012-09-20. Retrieved 2011-02-01.
^ COMETS!: Visitors from Deep Space pg77
^ Horizons output. "Observer Table for Comet C/1975 V1-A (West)". Retrieved 2019-02-25. (Observer Location:@sun)