Kreutz Sungrazers
Encyclopedia
Sungrazing comet
A sungrazing comet is a comet that passes extremely close to the Sun at perihelion – sometimes within a few thousand kilometres of the Sun's surface. While small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages...
s, characterized by orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
s taking them 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. They are believed to be fragments of one large comet
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 broke up several centuries ago and are named for German astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
Heinrich Kreutz
Heinrich Kreutz
Heinrich Carl Friedrich Kreutz was a German astronomer, most notable for his studies of the orbits of several sungrazing comets, which revealed that they were all related objects, produced when a very large sun-grazing comet fragmented several hundred years previously...
, who first demonstrated that they were related.
Several members of the Kreutz family have become 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, occasionally visible near the Sun in the daytime sky. The most recent of these was Comet Ikeya–Seki in 1965, which may have been one of the brightest comets in the last millennium
Millennium
A millennium is a period of time equal to one thousand years —from the Latin phrase , thousand, and , year—often but not necessarily related numerically to a particular dating system....
. It has been suggested that another cluster of bright Kreutz system comets may begin to arrive in the inner Solar System in the next few years to decades.
Many hundreds of smaller members of the family, some only a few meters across, have been discovered 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. None of these smaller comets has survived its perihelion passage. Amateur astronomer
Amateur astronomy
Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
s have been successful at discovering Kreutz comets in the data available in real time via the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
.
Discovery and historical observations
C/1680 V1
C/1680 V1, also called the Great Comet of 1680, Kirch's Comet, and Newton's Comet, has the distinction of being the first comet discovered by telescope. Discovered by Gottfried Kirch on 14 November 1680, New Style, it became one of the brightest comets of the 17th century--reputedly visible even in...
. This comet was found to have passed just 200,000 km (0.0013 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
) above the sun's surface, equivalent to about half the distance between the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. It thus became the first known sungrazing comet
Sungrazing comet
A sungrazing comet is a comet that passes extremely close to the Sun at perihelion – sometimes within a few thousand kilometres of the Sun's surface. While small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages...
. Its perihelion distance was just 1.3 solar radii.
Astronomers at the time, including Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...
, speculated that this comet was a return of a bright comet seen close to the Sun in the sky in 1106. 163 years later, the Great Comet of 1843
Great Comet of 1843
The Great Comet of 1843 formally designated C/1843 D1 and 1843 I, was a long-period comet which became very bright in March 1843 . It was discovered on February 5, 1843 and rapidly brightened to become a great comet...
appeared and also passed extremely close to the Sun. Despite orbital calculations showing that it had a period of several centuries, some astronomers wondered if it was a return of the 1680 comet. A bright comet seen in 1880 was found to be travelling on an almost identical orbit to that of 1843, as was the subsequent Great Comet of 1882
Great Comet of 1882
The Great Comet of 1882 formally designated C/1882 R1, 1882 II, and 1882b, was a comet which became very bright in September 1882...
. Some astronomers suggested that perhaps they were all one comet, whose orbital period was somehow being drastically shortened at each perihelion passage, perhaps by retardation by some dense material surrounding the Sun.
An alternative suggestion was that the comets were all fragments of an earlier sun-grazing comet. This idea was first proposed in 1880, and its plausibility was amply demonstrated when the Great Comet of 1882 broke up into several fragments after its perihelion passage. In 1888, Heinrich Kreutz published a paper showing that the comets of 1843 (C/1843 D1, the Great March Comet), 1880 (C/1880 C1, the Great Southern Comet), and 1882 (C/1882 R1, Great September Comet) were probably fragments of a giant comet that had broken up several revolutions before. The comet of 1680 proved to be unrelated to this family of comets.
After another Kreutz Sungrazer was seen in 1887 (C/1887 B1, the Great Southern Comet of 1887
Great Southern Comet of 1887
The Great Southern Comet of 1887, or C/1887 B1 using its International Astronomical Union designation, was a bright comet seen from the Southern Hemisphere during January 1887. Later calculations indicated it to be part of the Kreutz Sungrazing group....
), the next one did not appear until 1945. Two further sungrazers appeared in the 1960s, Comet Pereyra
Comet Pereyra
Comet Pereyra was a bright comet which appeared in 1963. It was a member of the Kreutz Sungrazers, a group of comets which pass extremely close to the Sun.- Discovery :...
in 1963 and Comet Ikeya–Seki, which became extremely bright in 1965, and broke into three pieces after its perihelion. The appearance of two Kreutz Sungrazers in quick succession inspired further study of the dynamics of the group.
Notable members
The brightest members of the Kreutz Sungrazers have been spectacular, easily visible in the daytime sky. The three most impressive have been the Great Comet of 1843Great Comet of 1843
The Great Comet of 1843 formally designated C/1843 D1 and 1843 I, was a long-period comet which became very bright in March 1843 . It was discovered on February 5, 1843 and rapidly brightened to become a great comet...
, the Great Comet of 1882
Great Comet of 1882
The Great Comet of 1882 formally designated C/1882 R1, 1882 II, and 1882b, was a comet which became very bright in September 1882...
and Comet Ikeya–Seki. Another notable Kreutz Sungrazer was the Eclipse Comet of 1882 (see further below).
The Great Comet of 1843
The Great Comet of 1843 was first noticed in early February of that year, just over three weeks before its perihelion passage. By February 27 it was easily visible in the daytime sky, and observers described seeing a tail 2–3° long stretching away from the sun before being lost in the glare of the sky. After its perihelion passage, it reappeared in the morning sky, and developed an extremely long tail. It extended about 45° across the sky on March 11 and was more than 2° wide; the tail was calculated to be more than 300 million kilometers (2 AU) long. This held the record for the longest measured cometary tail until 2000, when Comet HyakutakeComet Hyakutake
Comet Hyakutake is a comet, discovered on January 31, 1996, which passed very close to Earth in March of that year. It was dubbed The Great Comet of 1996; its passage near the Earth was one of the closest cometary approaches of the previous 200 years. Hyakutake appeared very bright in the night...
's tail was found to stretch to some 550 million kilometers in length. (The Earth–Sun distance—1 AU—is only 150 million kilometers.)
The comet was very prominent throughout early March, before fading away to almost below naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
visibility by the beginning of April. It was last detected on April 20. This comet apparently made a substantial impression on the public, inspiring in some a fear that judgement day was imminent.
The Eclipse Comet of 1882
A party of observers gathered in EgyptEgypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
to watch a solar eclipse
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
in May 1882 were greatly surprised when they observed a bright streak near to the Sun once totality began. By a remarkable coincidence, the eclipse had coincided with the perihelion passage of a Kreutz comet. The comet would otherwise have gone unnoticed — its sighting during the eclipse was the only observation of it. Photographs of the eclipse revealed that the comet had moved noticeably during the 1m50s eclipse, as would be expected for a comet racing past the Sun at almost 500 km/s. The comet is sometimes referred to as Tewfik, after Tewfik Pasha
Tewfik Pasha
HH Muhammed Tewfik Pasha ' was Khedive of Egypt and Sudan between 1879 and 1892, and the sixth ruler from the Muhammad Ali Dynasty.-Early life:...
, the Khedive of Egypt at the time.
The Great Comet of 1882
Great Comet of 1882
The Great Comet of 1882 formally designated C/1882 R1, 1882 II, and 1882b, was a comet which became very bright in September 1882...
was discovered independently by many observers, as it was already easily visible to the naked eye when it appeared in early September 1882, just a few days before perihelion. It grew rapidly brighter and was eventually so bright it was visible in the daytime for two days (16–17 September), even being seen through light cloud.
After its perihelion passage, the comet remained bright for several weeks. During October, its nucleus was seen to fragment into first two and then four pieces. Some observers also reported seeing diffuse patches of light several degrees away from the nucleus. The rate of separation of the fragments of the nucleus was such that they will return about a century apart, between 670 and 960 years after the break-up.
Comet Ikeya–Seki
Comet Ikeya–Seki is the most recent very bright Kreutz sungrazer. It was discovered independently by two JapanJapan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese amateur astronomers on September 18, 1965, within 15 minutes of each other, and quickly recognised as a Kreutz Sungrazer. It brightened rapidly over the following four weeks as it approached the sun, and reached apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
2 by October 15. Its perihelion passage occurred on October 21, and observers across the world easily saw it in the daytime sky. A few hours before perihelion passage on October 21 it had a visible magnitude from −10 to −11, comparable to the first quarter
Lunar phase
A lunar phase or phase of the moon is the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases change cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun...
of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and brighter than any other comet seen since 1106. A day after perihelion its magnitude decreased to just −4.
Japanese astronomers using a coronagraph
Coronagraph
A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved...
saw the comet break into three pieces 30 minutes before perihelion. When the comet reappeared in the morning sky in early November, two of these nuclei were definitely detected with the third suspected. The comet developed a very prominent tail, about 25° in length, before fading throughout November. It was last detected in January 1966.
Dynamical history and evolution
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
of perihelion at 280–282°, with a couple of outlying points probably due to uncertain orbital calculations. A greater range of values existed for the argument of perihelion
Argument of periapsis
The argument of periapsis , symbolized as ω, is one of the orbital elements of an orbiting body...
and longitude of the ascending node
Longitude of the ascending node
The longitude of the ascending node is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the origin of longitude, to the direction of the ascending node, measured in a reference plane...
.
Marsden found that the Kreutz Sungrazers could be split into two groups, with slightly different orbital elements, implying that the family resulted from fragmentations at more than one perihelion. Tracing back the orbits of Ikeya–Seki and the Great Comet of 1882, Marsden found that at their previous perihelion passage, the difference between their orbital elements was of the same order of magnitude as the difference between the elements of the fragments of Ikeya–Seki after it broke up. This meant it was realistic to presume that they were two parts of the same comet which had broken up one orbit ago. By far the best candidate for the progenitor comet was that seen in 1106 (Great Comet of 1106): Ikeya–Seki's derived orbital period gave a previous perihelion almost exactly at the right time, and while the Great Comet of 1882's derived orbit implied a previous perihelion a few decades later, it would only require a small error in the orbital elements to bring it into agreement.
The sungrazing comets of 1668, 1689, 1702 and 1945 seem to be closely related to those of 1882 and 1965, although their orbits are not well enough determined to establish whether they broke off from the parent comet in 1106, or the previous perihelion passage before that, some time in the 3–5th centuries AD. This subgroup of comets is known as Subgroup II. Comet White–Ortiz–Bolelli, which was seen in 1970, is more closely related to this group than Subgroup I, but appears to have broken off during the previous orbit to the other fragments.
The sungrazing comets observed in 1843 (Great Comet of 1843) and 1963 (Comet Pereyra
Comet Pereyra
Comet Pereyra was a bright comet which appeared in 1963. It was a member of the Kreutz Sungrazers, a group of comets which pass extremely close to the Sun.- Discovery :...
) seem to be closely related and belong to the subgroup I, although when their orbits are traced back to one previous perihelion, the differences between the orbital elements are still rather large, probably implying that they broke apart from each other one revolution before that. They may not be related to the comet of 1106, but rather a comet that returned about 50 years before that. Subgroup I also includes comets seen in 1695, 1880 (Great Southern Comet of 1880) and in 1887 (Great Southern Comet of 1987), as well as the vast majority of comets detected by SOHO mission (see below).
The distinction between the two sub-groups is thought to imply that they result from two separate parent comets, which themselves were once part of a 'grandparent' comet which fragmented several orbits previously. One possible candidate for the grandparent is a comet observed 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. Ephorus claimed to have seen this comet break into two. However modern astronomers are skeptical of the claims of Ephorus, because they were not confirmed by other sources. Instead comets that arrived between 3rd and 5th centuries AD (comets of 214, 426 and 467) are considered as possible progenerators of the Kreutz family. The original comet must certainly have been very large indeed, perhaps as large as 100 km across (for comparison, the nucleus of Comet Hale–Bopp was about 40 km across).
Although its orbit is rather different from those of the main two groups, it is possible that the comet of 1680 is also related to the Kreutz Sungrazers via a fragmentation many orbits ago.
The Kreutz Sungrazers are probably not a unique phenomenon. Studies have shown that for comets with high orbital inclinations and perihelion distances of less than about 2 AU, the cumulative effect of gravitational perturbations tends to result in sungrazing orbits. One study has estimated that Comet Hale–Bopp has about a 15% chance of eventually becoming a sun-grazing comet.
Recent observations
Until recently, it would have been possible for even a very bright member of the Kreutz Sungrazers to pass through the inner solar system unnoticed, if its perihelion had occurred between about May and August. At this time of year, as seen from EarthEarth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, the comet would approach and recede almost directly behind the sun, and could only become visible extremely close to the sun if it became very bright. Only a remarkable coincidence between the perihelion passage of the Eclipse Comet of 1882 and a total solar eclipse allowed its discovery.
However, during the 1980s, two Sun-observing satellites serendipitously discovered several new members of the Kreutz family, and 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...
Sun-observing satellite in 1995, it has been possible to observe comets very close to the sun at any time of year. The satellite provides a constant view of the immediate solar vicinity, and SOHO has now discovered hundreds of new sungrazing comets, some just a few metres across. About 83% of the sungrazers found by SOHO are members of the Kreutz group, with the other being referred to as 'non-Kreutz' or 'sporadic' sungrazers (Meyer, Marsden, and Kracht1&2 families). None of the sungrazers seen by SOHO has survived its perihelion passage; some may have plunged into the Sun itself, but most are likely to have simply evaporated away completely.
More than 75% of the SOHO sungrazers have been discovered by amateur astronomers analysing SOHO's observations via the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
. Some amateurs have managed remarkable numbers of discoveries, with Rainer Kracht of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
having chalked up 176 identifications, and Michael Oates of the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
making 144 discoveries. As of October 2008, 1500 Kreutz Sungrazers have been identified.
SOHO observations have shown that Sungrazers frequently arrive in pairs separated by a few hours. These pairs are too frequent to occur by chance, and cannot be due to break-ups on the previous orbit, because the fragments would have separated by a much greater distance. Instead, it is thought that the pairs result from fragmentations far away from the perihelion. Many comets have been observed to fragment far from perihelion, and it seems that in the case of the Kreutz Sungrazers, an initial fragmentation near perihelion can be followed by an ongoing 'cascade' of break-ups throughout the rest of the orbit.
The number of Subgroup I Kreutz comets discovered is about four times the number of Subgroup II members. This suggests that the 'grandparent' comet split into parent comets of unequal size.
Future
Dynamically, the Kreutz sungrazers might continue to be recognised as a distinct family for many thousands of years yet. Eventually their orbits will be dispersed by gravitational perturbations, although depending on the rate of fragmentation of the constituent parts, the group might be completely destroyed before it is gravitationally dispersed. The continuing discovery of large numbers of the smaller members of the family by SOHO will undoubtedly lead to a greater understanding of how comets break up to form families.As of October 2008, the last Kreutz Sungrazer to become bright was Comet White–Ortiz–Bolelli in 1970. It is not possible to estimate the chances of another very bright Kreutz comet arriving in the near future, but given that at least 10 have reached naked eye visibility over the last 200 years, another great comet from the Kreutz family seems almost certain to arrive at some point.
Further reading
- Marsden B. G. (1989), The Sungrazing Comets Revisited, Asteroids, comets, meteors III, Proceedings of meeting (AMC 89), Uppsala: Universitet, 1990, eds C. I. Lagerkvist, H. Rickman, B. A. Lindblad., p. 393