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Comet

Longmore

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77P/Longmore

Where is it now

Distance from Sun
4.887 AU
True anomaly
183.67°
Distance from Earth
3.909 AU
As of
22 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.

Orbit of Mercury Orbit of Venus Orbit of Mars Sun Earth — 0.995 AU from the Sun Earth Longmore — 4.887 AU from the Sun Longmore
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Longmore is 3.909 AU from Earth today (32.5 light-minutes).

In the sky

Right ascension
01h 55m 21s
Declination
+22° 59′ 10″
Constellation
Aries
Distance from Earth
3.91 AU
Elongation from the Sun
168.31° — near opposition — up most of the night

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.

How do I find my coordinates?

Google Maps on a computer

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

Google Maps on a phone

  1. Press and hold the spot to drop a pin.
  2. 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
3.613 AU
Eccentricity
0.3542
Inclination
24.34°
Orbital period
6.87 years
Perihelion
2.333 AU
Aphelion
4.892 AU
Longitude of ascending node
14.89°
Argument of periapsis
196.95°
Epoch · J2000
2456696.5
Orbit class · JFc
Jupiter-family comet (P < 20 y)
Earth MOID · 521.1 LD
1.3389 AU
Tisserand (Jupiter)
2.86

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
2,631
Data arc
50.25 years
First observed
11 August 1975
Last observed
9 November 2025
Residual RMS
0.8 ″
Solution · Shantanu Naidu
8 September 2026

Physical properties

Mean radius
4.10 km

Visual & observation

Absolute magnitude (H)
9.2
Total magnitude M₁ · K₁ 14.5
9.2

Discovery & classification

Discovered by
Longmore, Andrew Jonathan
Discovery date
10 June 1975
Discovery site
Siding Spring Observatory, Australia

Also known as 77P · 1974 XIV · 1975g · 1981 XVI · 1981a · 1988 XVIII · 1994q · 77P/1975 L1

Named

Close approaches 12 on record

When (UTC) Body Distance Lunar distances Relative speed
2046-10-15 13:47:00 Juptr 0.3132 AU 121.9 LD 6.2 km/s
2046-10-15 13:47:00 Jupiter 0.3132 AU 121.9 LD 6.2 km/s
2058-10-10 04:13:00 Juptr 1.8566 AU 722.5 LD 10.6 km/s
2118-03-24 03:14:00 Juptr 0.9947 AU 387.1 LD 6.1 km/s
2129-09-14 21:53:00 Jupiter 0.3476 AU 135.3 LD 7 km/s
2129-09-14 21:53:00 Juptr 0.3476 AU 135.3 LD 7 km/s
2177-02-16 15:26:00 Juptr 0.4028 AU 156.7 LD 7 km/s
2177-02-16 15:26:00 Jupiter 0.4028 AU 156.7 LD 7 km/s

Next ten from today. 1 lunar distance = 384,400 km. Source: JPL close-approach data.

Sources