Ikeya–Seki and the Kreutz sungrazers
A family of comets that skim the surface of the Sun, including Ikeya–Seki, one of the brightest comets of the last thousand years.
Key facts
- Designation
- C/1965 S1 (Ikeya–Seki) and the Kreutz group
- Type
- Sungrazing comets
- Orbital period
- about 500 to 1,000 years for the larger members
- Closest to the Sun
- about 450,000 km above the Sun's surface for Ikeya–Seki
- Farthest from the Sun
- about 100 to 200 AU
- Tilt of orbit
- about 142° (retrograde)
- Nucleus
- Ikeya–Seki perhaps a few kilometres; most Kreutz comets are only metres to tens of metres
- Discovered
- Ikeya–Seki by Kaoru Ikeya and Tsutomu Seki in Japan on 18 September 1965
- Returns
- Ikeya–Seki passed the Sun on 21 October 1965 and broke into pieces
Orbit
The Kreutz sungrazers all follow nearly the same orbit, which brings them within about a solar radius of the Sun's surface, so close that they pass through the Sun's outer atmosphere. Heinrich Kreutz, a German astronomer, showed in the 1880s that several great comets shared this path and must be pieces of one parent that broke up long ago. Many astronomers suspect the parent was a great comet seen in the fourth century BC, but this cannot be proved.
Size and nature
The largest pieces can survive their pass and become dazzling. Ikeya–Seki was so bright in October 1965 that it was seen in daylight near the Sun. It split into at least three pieces at perihelion. Most Kreutz comets are tiny and are destroyed outright, evaporating in the Sun's heat.
History
Kaoru Ikeya and Tsutomu Seki, two young Japanese amateurs, found the comet independently within minutes of each other in September 1965. Other famous Kreutz comets include the Great Comets of 1843 and 1882 and Comet Lovejoy in 2011, which survived its pass to the surprise of astronomers.
Missions
The SOHO solar observatory, launched in 1995, uses a disc to block the Sun's glare and see its faint outer atmosphere. It has found more than 5,000 comets, the majority of them small Kreutz sungrazers falling to their end. Many were spotted in SOHO's public images by amateurs around the world.
Space missions
- SOHO A solar observatory that has become the greatest comet discoverer in history.
Key dates
| Date | What happened |
|---|---|
| 18 September 1965 | Kaoru Ikeya and Tsutomu Seki discovered the great sungrazing comet Ikeya–Seki. |
| 21 October 1965 | Comet Ikeya–Seki passed about 450,000 km above the Sun's surface. |
Did you know?
SOHO has found more comets than any other observatory in history.
Sungrazers lose so much material at once that some show metals such as iron and nickel glowing in their spectra.
Tsutomu Seki also discovered many asteroids and more comets from Kochi in Japan.