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Comet White-Ortiz-Bolelli

2007 Schools Wikipedia Selection. Related subjects: Space (Astronomy)

   Approximate relationship of the largest members of the Kreutz
   Sungrazers. Note that the perihelion passage at which fragmentations
   occurred may not be well established
   Enlarge
   Approximate relationship of the largest members of the Kreutz
   Sungrazers. Note that the perihelion passage at which fragmentations
   occurred may not be well established

   Comet White-Ortiz-Bolelli (formal designation: C/1970 K1) was a bright
   comet which appeared in 1970. It was a member of the Kreutz Sungrazers,
   a family of comets which resulted from the break-up of a large parent
   comet several centuries ago. It was already easily visible to the naked
   eye when first discovered, and reached a maximum apparent magnitude of
   1.

Discovery

   Comet White-Ortiz-Bolelli was first spotted on May 18 by Graeme White,
   an Australian amateur astronomer in Wollongong, New South Wales. He
   sighted the comet in binoculars shortly after sunset, and described it
   as having a star-like head at apparent magnitude 1-2, and a short tail
   about 1 degree long. He spotted it again on May 20 by naked 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 by Air France pilot
   Emilio Ortiz, from a location about 400 km east of Madagascar. Ortiz
   saw the comet from his cockpit, and reported a magnitude of 0.5 to 1.0
   and a tail about 5–8° long. A few hours later, Carlos Bolelli, a
   technician at the Cerro Tololo Inter-American Observatory in Chile
   became the third independent discoverer of the comet, although he saw
   only the tail, as the head was beneath the horizon.

Subsequent observations

   Numerous independent discoveries were made in the days immediately
   following the comet's discovery, but astronomical naming conventions
   only allowed the comet to be given the names of the first three. All
   sightings of the comet were made from the southern hemisphere, due to
   the orientation of its orbit with respect to the Earth.

   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-defined
   nebulosity. Increasing moonlight and the comet's decreasing brightness
   prevented any further visual sightings of the comet.

A sungrazer

   The comet's sudden appearance very close to the sun and rapid
   subsequent decline in brightness both pointed to it being a sungrazing
   comet, and calculations of its orbit by Brian Marsden backed this
   suggestion. Marsden showed that the comet had reached perihelion on May
   14, at a distance of just 1.35 million km, or 2 solar radii.

   The calculated orbit pinned down White-Ortiz-Bolelli as a member of the
   Kreutz 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 the Sun as seen from
   Earth; the only previous Kreutz Sungrazer seen during these months was
   the Eclipse Comet of 1882, which was only observed once, during a total
   solar 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.
   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.
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