Comet Ikeya Seki (C/1965 S1)

Discovered by:             Kaoru Ikeya and Tsutomu Seki
Discovery date:            September 18, 1965
Also known as:            The Great Comet of 1965
Peak magnitude:         -10.0
Aphelion (Part A):        183.2 AU (27.4 billion kilometres or 17.0 billion miles)
Aphelion (Part B):         207.4 AU (31.0 billion kilometres or 19.3 billion miles)
Perihelion (A):              0.00778 AU (1.16 million kilometers or 0.72 million miles)
Perihelion (B):              0.00778 AU (1.16 million kilometers or 0.72 million miles)
Semi-major axis (A):     91.6 AU (13.7 billion kilometres or 8.5 billion miles)
Semi-major axis (B):    103.7 AU (15.5 billion kilometres or 9.6 billion miles)
Eccentricity (A):           0.999915
Eccentricity (B):           0.999925
Orbital period (A):         876.7 years
Orbital period (B):         1056.1 years
Inclination (A):              141.9 degrees
Inclination (B):              141.9 degrees

Last perihelion:             October 21, 1965
Next perihelion:             2565 (estimate)

Comet Ikeya Seki photographed on October 30, 1965 (James W. Young - TMO/JPL/NASA)

Comet Ikeya–Seki is also known as the Great Comet of 1965.

Discovered independently on September 18, 1965 by Japanese astronomers Kaoru Ikeya and Tsutomu Seki.

Ikeya–Seki is a member of the Kreutz Sungrazers group of comets. These are believed to be fragments of a large comet that broke up in 1106.

At perihelion on October 21, 1965 it passed only 450,000 kilometres (280,000 miles) above the Sun's surface.

Reached magnitude –10 just before perihelion and was visible in daylight, appearing close to the Sun. 

Comet Ikeya–Seki was one of the brightest comets in recorded history and the brightest in the last millennium.

It broke into three pieces just before perihelion. The remains of the comet continued in almost identical orbits with it re-appearing in the morning sky in late October.

Spectacular naked-eye sight in late October with a beautiful long tail 60 degrees in length.

At its maximum length, Ikeya-Seki's tail extended for 113 million kilometers (70 million miles), ranking it as the fourth largest ever recorded. Only the Great Comets of 1680, 1811 and 1843 had longer tails.

Finally disappeared from view in early 1966.

Due to return around 2565 but with a shattered nucleus impossible to predict a repeat performance.