The Kreutz sungrazers ( KROYTS) are a family of sungrazing comets, characterized by orbits taking them extremely close to the Sun at perihelion. At the far extreme of their orbits, aphelion, Kreutz sungrazers can be a hundred times farther from the Sun than the Earth is, while their distance of closest approach can be less than twice the Sun's radius. 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 demonstrated that they were related. These sungrazers make their way from the distant outer Solar System to the inner Solar System, to their perihelion point near the Sun, and then leave the inner Solar System in their return trip to their aphelion. Several members of the Kreutz family have become great comets, 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. 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 decades. More than 5,000 members of the family have been discovered since the launch of the SOHO satellite in 1995. None of these smaller comets have survived their perihelion passage. Larger sungrazers such as the Great Comet of 1843 and C/2011 W3 (Lovejoy) have survived their perihelion passage. Amateur astronomers have been successful at discovering Kreutz comets in the data available in real time via the internet. Two of the most recent Kreutz comets include C/2026 A1 (MAPS) that comes to perihelion on 4 April 2026 and C/2024 S1 (ATLAS) that disintegrated in October 2024.
Discovery and historical observations The first comet whose orbit was recognized to take it extremely close to the Sun was the Great Comet of 1680. This comet was found to have passed about 235,000 kilometres (146,000 mi) above the Sun's surface, equivalent to around a sixth of Sun's diameter, or about half the distance between the Earth and the Moon. The Great Southern Comet of 1887 passed about 27,000 km (17,000 mi) from the surface of the Sun. Astronomers at the time, including Edmond Halley, speculated that the Great Comet of 1680 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 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 traveling on an almost identical orbit to that of 1843, as was the subsequent Great Comet of 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 orbits before. The comet of 1680 proved to be unrelated to this family of comets. It was a sungrazer, but not a member of the Kreutz group. After another Kreutz sungrazer was seen in 1887 (C/1887 B1, the Great Southern Comet of 1887), the next one did not appear until 1945. Two further sungrazers appeared in the 1960s, Comet Pereyra in 1963 and Comet Ikeya–Seki, which became extremely bright in 1965, and broke into three pieces after its perihelion. It is probably the most famous among the Kreutz sungrazers. The appearance of two Kreutz sungrazers in quick succession inspired further study of the dynamics of the group. Initially, the name "sungrazer" was applied exclusively to the Kreutz group.
Physical traits Most sungrazing comets are part of the Kreutz family. The group generally has an eccentricity approaching 1, orbital inclination of 139–144° (precluding close encounters with planets), a perihelion distance of less than 0.01 AU (less than the diameter of the Sun), an aphelion distance of about 100 AU (15 billion km) and an orbital period of about 500–1,000 years. Erosion of the comets by solar energy during close passages leads to progressive changes in their orbits. Most Kreutz sungrazers have radii of less than 100 metres (330 ft), but the brightest ones reach radii of 1–10 kilometres (0.62–6.21 mi). The bodies themselves have irregular shapes and appearances which have been described as diffuse, star-like or tailed. The material that makes up their cometary nuclei has a low tensile strength. They have only low concentrations of volatiles and thus become active only close to the Sun, since they have lost most of their volatiles during earlier transits. Their brightness may peak shortly before perihelion at 10–15 solar radii, after which they become dimmer. This may be due to the evaporation of minerals like olivine and pyroxene. Other studies find a more chaotic pattern of brightening and darkening. The water and organic materials of a comet evaporate first, exposing fluffy aggregations of olivines that form dust tails. Dust from these comets remains in the solar corona, where it interacts with the Sun's magnetic field.
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 1843, the Great Comet of 1882 and X/1106 C1. The progenitor of all Kreutz sungrazers observed to date may be the Great Comet of 371 BC, or comets seen in 214 BC, 423 AD or 467 AD. Another notable Kreutz sungrazer was the Eclipse Comet of 1882. Other candidate Kreutz sungrazers are comets observed in 582 AD in China and Europe, X/1381 V1 which was seen from Japan, Korea, Russia and Egypt, two comets seen in 1668 and 1695, C/1880 C1, the Great Southern Comet of 1887, C/1945 X1 (du Toit), C/1970 K1 and C/2005 S1, one of the best-observed Kreutz sungrazers.
Great Comet of 371 BC
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