| Discovery[1][2] | |
|---|---|
| Discovered by | Graeme White Emilio Ortiz Carlos Bolelli |
| Discovery date | 18 May 1970 |
| Designations | |
| 1970 VI, 1970f[3] | |
| Orbital characteristics[4] | |
| Epoch | 29 May 1970 (JD 2440735.5) |
| Observation arc | 14 days |
| Earliestprecovery date | 16 May 1970 |
| Number of observations | 9 |
| Orbit type | Kreutz sungrazer |
| Aphelion | 347.565 AU |
| Perihelion | 0.00884 AU |
| Semi-major axis | 173.787 AU |
| Eccentricity | 0.99995 |
| Orbital period | 2,291.04 years |
| Inclination | 138.95° |
| 336.82° | |
| Argument of periapsis | 61.103° |
| Last perihelion | 14 May 1970 |
| TJupiter | –0.058 |
| EarthMOID | 0.4901 AU |
| JupiterMOID | 2.8494 AU |
| Physical characteristics[5] | |
Mean radius | 1.1 km (0.68 mi) |
| Mass | 2.10×1015 kg |
| 1.0 (1970 apparition) | |
Comet White–Ortiz–Bolelli (formal designations:C/1970 K1,1970 VI, and1970f) was a brightcomet which appeared in 1970. It was a member of theKreutz sungrazers,[6] a family of comets which resulted from the break-up of a large parent comet several centuries ago. It was already easily visible to thenaked eye when first discovered, and reached a maximumapparent magnitude of +1 (about as bright as planet Saturn).
Comet White–Ortiz–Bolelli was discovered on May 18 by Graeme White, anAustralian amateurastronomer inWollongong,New South Wales.[6] He sighted the comet inbinoculars shortly after sunset, and described it as having a star-like head atapparent magnitude 1-2, and a short tail about 1degree long. He spotted it again on May 20 bynaked eye as well as binoculars, and by this time the tail had grown to 10° in length.
The second independent discovery was made on May 21 byAir France pilot Emilio Ortiz, from a location about 400 km east ofMadagascar. Ortiz saw the comet from his cockpit, and reported a magnitude of 0.5 to 1.0 and a tail about 5–8° long.[6] A few hours later, Carlos Bolelli, a technician at theCerro Tololo Inter-American Observatory inChile became the third independent discoverer of the comet, although he saw only the tail, as the head was beneath the horizon.[6]
Numerous independent discoveries were made in the days immediately following the comet's discovery, butastronomical naming conventions only allowed the comet to be given the names of the first three. All sightings of the comet were made from theSouthern Hemisphere, due to the orientation of its orbit with respect to theEarth.
Throughout the comet's brief appearance, it could only be seen low in the sky for a short time after sunset, but it was most easily visible on May 24. After that it faded rapidly, and by 1 June it had already faded to below naked-eye visibility. The last definite detection of the comet was made on June 7, when it appeared as a faint, ill-definednebulosity. Increasingmoonlight and the comet's decreasing brightness prevented any further visual sightings of the comet.
The comet's sudden appearance very close to the Sun and rapid subsequent decline in brightness both pointed to it being asungrazing comet, and calculations of itsorbit byBrian G. Marsden backed this suggestion.[6] Marsden showed that the comet had reachedperihelion (closest approach to the Sun) on May 14, at a distance of just 0.0088 AU (1.32 million km), or 2solar radii.[4]
The calculated orbit pinned down White-Ortiz-Bolelli as a member of theKreutz sungrazers, a group of comets which all originate from the fragmentation of one giant parent comet several hundred years ago, and which has provided some of the brightest comets ever seen. Kreutz Sungrazers all travel on similar orbits, which result in them being most easily visible from the southern hemisphere, between August and April. Kreutz sungrazers appearing between May and July may come and go unseen, as they approach from directly behind theSun as seen from Earth; the only previous Kreutz Sungrazer seen during these months was theEclipse Comet of 1882, which was only observed once, during a totalsolar eclipse.
Before White–Ortiz–Bolelli, studies had divided the Kreutz Sungrazers into two sub-groups, originating from fragmentations at different orbits, but White-Ortiz-Bolelli seemed to be a member of neither.[7] Studies showed that it probably broke away from the comet that spawned Subgroup II, before the main fragmentation, and it was classed as the first (and so far only) member of Subgroup IIa.[7]
Having an observationarc of only 14 days,[4] the long-term trajectory of the comet is poorly constrained. The orbital period is basically unknown but assumed to be a few thousand years with anorbital inclination of 139 degrees.[4]
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