Sungrazing comet
Encyclopedia
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...
that passes extremely close to the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
at perihelion – sometimes within a few thousand kilometres of the Sun's surface. While small sungrazers can be completely evaporated
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
during such a close approach to the Sun, larger sungrazers can survive many perihelion passages. However, the strong evaporation and tidal force
Tidal force
The tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force per unit mass exerted on one body by a second body is not constant across its diameter, the side nearest to the second being more attracted by it than the side...
s they experience often lead to their fragmentation.
The Kreutz Sungrazers
The most famous sungrazers are the Kreutz SungrazersKreutz Sungrazers
The Kreutz Sungrazers are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. They are believed to be fragments of one large comet that broke up several centuries ago and are named for German astronomer Heinrich Kreutz, who first...
, which all originate from one giant comet that broke up into many smaller comets during its first passage through the inner solar system. An extremely bright comet seen by Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
and Ephorus
Ephorus
Ephorus or Ephoros , of Cyme in Aeolia, in Asia Minor, was an ancient Greek historian. Information on his biography is limited; he was the father of Demophilus, who followed in his footsteps as a historian, and to Plutarch's claim that Ephorus declined Alexander the Great's offer to join him on his...
in 371 BC is a possible candidate for this parent comet.
The Great Comet
Great comet
A Great Comet is a comet that becomes exceptionally bright. There is no official definition; often the term will be attached to comets that become bright enough to be noticed by casual observers who are not actively looking for them, and become well known outside the astronomical community. Great...
s of 1843 and 1882, and Comet Ikeya-Seki
Comet Ikeya-Seki
Comet Ikeya–Seki, formally designated C/1965 S1, 1965 VIII, and 1965f, was a long-period comet discovered independently by Kaoru Ikeya and Tsutomu Seki...
in 1965 were all fragments of the original comet. Each of these three was briefly bright enough to be visible in the daytime sky, next to the Sun, outshining even the full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...
.
In 1979, C/1979 Q1 (SOLWIND) was the first sungrazer to be spotted by US satellite P78-1
P78-1
P78-1 or Solwind was a United States satellite launched aboard an Atlas F rocket from Vandenberg Air Force Base in California on February 24, 1979. The satellite operated until September 13, 1985, when it was shot down in orbit by an F-15 Eagle fighter aircraft during an US Air Force ASM-135 ASAT...
, in coronographs taken on 30 and 31 Aug 1979.
Since the launch of the SOHO
Solar and Heliospheric Observatory
The Solar and Heliospheric Observatory is a spacecraft built by a European industrial consortium led by Matra Marconi Space that was launched on a Lockheed Martin Atlas IIAS launch vehicle on December 2, 1995 to study the Sun, and has discovered over 2100 comets. It began normal operations in May...
satellite in 1995, hundreds of tiny Kreutz Sungrazers have been discovered, all of which have either plunged into the sun or been destroyed completely during their perihelion passage. The Kreutz family of comets is apparently much larger than previously suspected. It will only be a matter of time before another large member of the group passes through the inner solar system and gives a display to rival the great Kreutz comets of the past.
Other sungrazers
About 83% of the sungrazers observed with SOHO are members of the Kreutz group. The other 17% contains some sporadic sungrazers, but three other related groups of comets have been identified among them: the Kracht, Marsden and Meyer groups. The Marsden and Kracht groups both appear to be related to Comet 96P/Machholz96P/Machholz
Comet 96P/Machholz or 96P/Machholz 1 is a short-period comet discovered on May 12, 1986 by amateur astronomer Donald Machholz in Loma Prieta, California. Comet 96P/Machholz will next come to perihelion on July 14, 2012....
, which is also the parent of two meteor
METEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
streams, the Quadrantids
Quadrantids
The Quadrantids are an easily visible January meteor shower.The radiant of this shower is an area inside the constellation Boötes. The name comes from Quadrans Muralis, an obsolete constellation that is now part of Boötes...
and the Arietids
Arietids
The Arietids are a strong meteor shower that lasts from May 22 to July 2 each year, and peaks on June 7. The Arietids, along with the Zeta Perseids, are the most intense daylight meteor showers of the year...
. It is considered that both Marsden and Kracht groups have a small period, but Meyer group rather have intermediate or long period because Meyer comets have high orbit inclination.
The Great Comet of 1680 was a sungrazer and while used by Newton to verify Kepler's equations on orbital motion, it was not a member of any larger groups.
Origin of sungrazing comets
Studies show that for comets with high orbital inclinations and perihelion distances of less than about 2 astronomical unitAstronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s, the cumulative effect of gravitational perturbations over many orbits is adequate to reduce the perihelion distance to very small values. One study has suggested that Comet Hale-Bopp
Comet Hale-Bopp
Comet Hale–Bopp was perhaps the most widely observed comet of the 20th century, and one of the brightest seen for many decades...
has about a 15% chance of eventually becoming a sungrazer.