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Comet

Lemmon

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C/2021 T4 (Lemmon)

Lemmon is a comet in the Comet orbit class. Its orbit takes it from 1.48 AU to 36,262.09 AU from the Sun; one orbit takes 2,441,569.6 years. Orbit from the JPL solution of 14 April 2025.

Where is it now

Distance from Sun
11.004 AU
True anomaly
136.93°
Distance from Earth
11.48 AU
As of
25 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.

Sun Earth — 0.994 AU from the Sun Earth Lemmon — 11.004 AU from the Sun Lemmon
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Lemmon is 11.48 AU from Earth today (1.6 light-hours).

In the sky

Right ascension
10h 55m 00s
Declination
+26° 01′ 18″
Constellation
Leo Minor
Distance from Earth
11.47 AU
Elongation from the Sun
59.88° — near the Sun — look low at dusk or dawn

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
18,131.787 AU
Eccentricity
0.9999
Inclination
160.78°
Orbital period
2,441,569.6 years
Perihelion
1.483 AU
Aphelion
36,262.09 AU
Longitude of ascending node
257.88°
Argument of periapsis
329.81°
Epoch · J2000
2460048.5
Orbit class · COM
Comet
Earth MOID · 193.6 LD
0.4975 AU
Tisserand (Jupiter)
-1.426

Orbit quality

Observations used
1,259
Data arc
3.63 years
First observed
7 August 2021
Last observed
24 March 2025
Residual RMS
0.69 ″
Solution · Otto Matic
14 April 2025

Visual & observation

Absolute magnitude (H)
12.4
Total magnitude M₁ · K₁ 4.5
12.4

Discovery & classification

Also known as 2021 T4

Named

Sources