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Comet

Hartley

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110P/Hartley 3

Where is it now

Distance from Sun
4.057 AU
True anomaly
230.69°
Distance from Earth
3.738 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 Hartley — 4.057 AU from the Sun Hartley
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Hartley is 3.738 AU from Earth today (31.1 light-minutes).

In the sky

Right ascension
20h 45m 20s
Declination
-09° 57′ 02″
Constellation
Aquarius
Distance from Earth
3.74 AU
Elongation from the Sun
101.22° — 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.

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
3.604 AU
Eccentricity
0.3163
Inclination
11.7°
Orbital period
6.84 years
Perihelion
2.464 AU
Aphelion
4.744 AU
Longitude of ascending node
287.53°
Argument of periapsis
167.39°
Epoch · J2000
2458260.5
Orbit class · JFc
Jupiter-family comet (P < 20 y)
Earth MOID · 576.7 LD
1.482 AU
Tisserand (Jupiter)
2.99

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
2,428
Data arc
13.01 years
First observed
11 August 2013
Last observed
14 August 2026
Residual RMS
0.52 ″
Solution · Davide Farnocchia
4 September 2026

Physical properties

Mean radius
2.15 km
Rotation period
10.15 hours

Visual & observation

Absolute magnitude (H)
4.9
Total magnitude M₁ · K₁ 25.3
4.9

Discovery & classification

Discovered by
Hartley, Malcolm
Discovery date
19 February 1988
Discovery site
U. K. Schmidt Telescope, Siding Spring

Also known as 110P · 110P/1988 D1 · 110P/1993 M1 · 1987 XII · 1988d · 1993m · 1994 XII

Named

Close approaches 8 on record

When (UTC) Body Distance Lunar distances Relative speed
2032-03-13 23:17:00 Juptr 0.7073 AU 275.3 LD 3.9 km/s
2091-05-29 01:49:00 Juptr 0.6341 AU 246.8 LD 3.5 km/s
2138-12-11 06:32:00 Juptr 0.426 AU 165.8 LD 3.7 km/s
2138-12-11 06:32:00 Jupiter 0.426 AU 165.8 LD 3.7 km/s
2174-11-11 16:36:00 Juptr 1.8862 AU 734.1 LD 7.4 km/s
2195-10-21 03:24:00 Juptr 1.9424 AU 755.9 LD 2.7 km/s

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

Sources