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Comet

Siding Spring

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C/2004 T3 (Siding Spring)

Siding Spring is a comet in the Comet orbit class. Its orbit takes it from 8.86 AU to 11,606.64 AU from the Sun; one orbit takes 442,608.9 years. Orbit from the JPL solution of 9 June 2026.

Where is it now

Distance from Sun
39.163 AU
True anomaly
123.26°
Distance from Earth
38.334 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 Siding Spring — 39.163 AU from the Sun Siding Spring
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Siding Spring is 38.334 AU from Earth today (5.3 light-hours).

In the sky

Right ascension
03h 19m 25s
Declination
+41° 24′ 48″
Constellation
Perseus
Distance from Earth
38.33 AU
Elongation from the Sun
146.58° — 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
5,807.75 AU
Eccentricity
0.9985
Inclination
71.96°
Orbital period
442,608.9 years
Perihelion
8.864 AU
Aphelion
11,606.637 AU
Longitude of ascending node
50.35°
Argument of periapsis
259.69°
Epoch · J2000
2453411.5
Orbit class · COM
Comet
Earth MOID · 3,315.4 LD
8.5191 AU
Tisserand (Jupiter)
1.143

Orbit quality

Observations used
110
Data arc
476 days
First observed
12 October 2004
Last observed
31 January 2006
Residual RMS
0.57 ″
Solution · Otto Matic
9 June 2026

Visual & observation

Absolute magnitude (H)
6.4
Total magnitude M₁ · K₁ 7.3
6.4

Discovery & classification

Also known as 2004 T3

Named

Sources