brightness has been found at about 7 solar radii from the sun and it is possibly due to a fragmentation of the comet nucleus. An alternative explanation is that the brightness peak at 12 solar radii comes from the sublimation of amorphous olivines and the peak at 11.2 solar radii is from the sublimation of crystalline olivines. The peak at 7 solar radii could then be the sublimation of pyroxene. Sungrazing groups Kreutz Sungrazers The most famous sungrazers are the Kreutz Sungrazers, 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 and Ephorus in 371 BC is a possible candidate for this parent comet. The Great Comets of 1843 and 1882, Comet Ikeya–Seki in 1965 and C/2011 W3 (Lovejoy) in 2011 were all fragments of the original comet. Each of these four was briefly bright enough to be visible in the daytime sky, next to the Sun, 1882's comet outshining even the full moon. In 1979, C/1979 Q1 (SOLWIND) was the first sungrazer to be spotted by US satellite P78-1, in coronagraphs taken on 30 and 31 Aug 1979. Apart from Comet Lovejoy, 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. 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/Machholz. These comets have also been linked to several meteor streams, including the Daytime Arietids, the delta Aquariids, and the Quadrantids. Linked comet orbits suggest that both Marsden and Kracht groups have a small period, on the order of five years, but the Meyer group may have intermediate- or long-period orbits. The Meyer group comets are typically small, faint, and never have tails. 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. However, comet C/2012 S1 (ISON), which disintegrated shortly before perihelion, had orbital elements similar to the Great Comet of 1680 and