Comet

Thatcher

C/1861 G1 (Thatcher)

Thatcher is a comet in the Comet orbit class. Its orbit takes it from 0.92 AU to 110.44 AU from the Sun; one orbit takes 415 years.

Where is it now

Distance from Sun: 107.589 AU
True anomaly: 178.29°
Distance from Earth: 106.746 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. Thatcher is 106.746 AU from Earth today (14.8 light-hours).

In the sky

Right ascension: 01h 29m 39s
Declination: +43° 31′ 04″
Constellation: Andromeda
Distance from Earth: 106.74 AU
Elongation from the Sun: 148° — well clear of the Sun

Favours the northern hemisphere; low or below the horizon from far south.

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: 55.682 AU
Eccentricity: 0.9835
Inclination: 79.77°
Orbital period: 415 years
Perihelion: 0.921 AU
Aphelion: 110.443 AU
Longitude of ascending node: 31.87°
Argument of periapsis: 213.45°
Epoch · J2000: 2400920.5
Orbit class · COM: Comet
Tisserand (Jupiter): 0.304

Orbit quality

Observations used: 187
Data arc: 149 days
First observed: 11 April 1861
Last observed: 7 September 1861

Discovery & classification

Also known as 1861 G1

Named

Sources

orbital elements: JPL SBDB