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Comet

McNaught-Hartley

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C/1999 T1 (McNaught-Hartley)

McNaught-Hartley is a comet in the Comet orbit class. Its orbit takes it from 1.17 AU to 16,246.68 AU from the Sun; one orbit takes 732,246.4 years. Orbit from the JPL solution of 15 April 2021.

Where is it now

Distance from Sun
47.99 AU
True anomaly
162.05°
Distance from Earth
47.321 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 McNaught-Hartley — 47.99 AU from the Sun McNaught-Hartley
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. McNaught-Hartley is 47.321 AU from Earth today (6.6 light-hours).

In the sky

Right ascension
22h 45m 06s
Declination
+28° 14′ 40″
Constellation
Pegasus
Distance from Earth
47.33 AU
Elongation from the Sun
131.38° — 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.

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
8,123.927 AU
Eccentricity
0.9999
Inclination
79.98°
Orbital period
732,246.4 years
Perihelion
1.172 AU
Aphelion
16,246.683 AU
Longitude of ascending node
182.48°
Argument of periapsis
344.76°
Epoch · J2000
2451866.5
Orbit class · COM
Comet
Earth MOID · 75.5 LD
0.194 AU
Tisserand (Jupiter)
0.234

Orbit quality

Observations used
661
Data arc
787 days
First observed
7 October 1999
Last observed
2 December 2001
Residual RMS
0.76 ″
Solution · Otto Matic
15 April 2021

Visual & observation

Absolute magnitude (H)
8.3
Total magnitude M₁ · K₁ 7.5
8.3

Discovery & classification

Also known as 1999 T1

Named

Sources