Comet

Ikeya-Seki

C/1965 S1-A (Ikeya-Seki)

Ikeya-Seki is a comet in the Comet orbit class. Its orbit takes it from 0.01 AU to 183.19 AU from the Sun; one orbit takes 880 years.

Where is it now

Distance from Sun: 78.282 AU
True anomaly: 179.14°
Distance from Earth: 78.045 AU
As of: 24 October 2026

Two-body Kepler propagation — accurate to ~0.1% for major planets over decades, less so for highly-perturbed bodies. Use JPL Horizons for high precision.

Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Ikeya-Seki is 78.045 AU from Earth today (10.8 light-hours).

In the sky

Right ascension: 06h 49m 27s
Declination: -12° 18′ 07″
Constellation: Canis Major
Distance from Earth: 78.04 AU
Elongation from the Sun: 104.02° — well clear of the Sun

Visible from both hemispheres.

From your location

See how high it is right now, whether it is up after civil twilight, and when it rises and sets where you are.

Paste a location

How do I find my coordinates?

Google Maps on a computer

Right-click the spot where you'll be observing.
The first line of the menu is the coordinates, e.g. 51.50722, -0.12758 — click it and they're copied.
Paste them above.

Google Maps on a phone

Press and hold the spot to drop a pin.
The coordinates appear in the search bar (or on the pin's card) — tap to copy, then paste above.

A full Google Maps link works too, but the short maps.app.goo.gl share links don't carry coordinates — copy the numbers instead. We round to about a kilometre; that's all the sky calculation needs.

Know your what3words address? Paste it, e.g. ///filled.count.soap. This is optional — the three words are sent to what3words to convert them, and we don't store the address or the result.

Your location stays in your browser and is sent only for this calculation. Using a what3words address is optional; if you do, the three words go to what3words to be converted and we don't record them. Set a location first, then you can save an email alert for this object. See our privacy policy.

Two-body approximation, good to about a degree for the planets — enough to find the constellation and know whether it is up.

Orbital elements

Semi-major axis: 91.6 AU
Eccentricity: 0.9999
Inclination: 141.86°
Orbital period: 880 years
Perihelion: 0.008 AU
Aphelion: 183.192 AU
Longitude of ascending node: 346.99°
Argument of periapsis: 69.05°
Epoch · J2000: 2439040.5
Orbit class · COM: Comet
Tisserand (Jupiter): -0.029

Orbit quality

Observations used: 119
Data arc: 115 days
First observed: 21 September 1965
Last observed: 14 January 1966

Discovery & classification

Also known as 1965 S1-A

Named

Sources

orbital elements: JPL SBDB