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Comet

SWAN

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C/2021 D1 (SWAN)

SWAN is a comet in the Comet orbit class. Its orbit takes it from 0.9 AU to 191.97 AU from the Sun; one orbit takes 947 years. Orbit from the JPL solution of 6 July 2021.

Where is it now

Distance from Sun
16.647 AU
True anomaly
154.23°
Distance from Earth
17.384 AU
As of
24 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 SWAN — 16.647 AU from the Sun SWAN
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. SWAN is 17.384 AU from Earth today (2.4 light-hours).

In the sky

Right ascension
11h 08m 22s
Declination
-17° 37′ 20″
Constellation
Crater
Distance from Earth
17.38 AU
Elongation from the Sun
41.6° — near the Sun — look low at dusk or dawn

Favours the southern hemisphere; low or below the horizon from far north.

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
96.437 AU
Eccentricity
0.9906
Inclination
31.46°
Orbital period
947 years
Perihelion
0.902 AU
Aphelion
191.972 AU
Longitude of ascending node
311.27°
Argument of periapsis
72.22°
Epoch · J2000
2459292.5
Orbit class · COM
Comet
Earth MOID · 82.8 LD
0.2127 AU
Tisserand (Jupiter)
1.056

Orbit quality

Orbit reasonably well determined (uncertainty code 5).

Observations used
342
Data arc
72 days
First observed
28 February 2021
Last observed
11 May 2021
Residual RMS
0.72 ″
Solution · Javier Roa
6 July 2021

Visual & observation

Absolute magnitude (H)
13.3
Total magnitude M₁ · K₁ 14.5
13.3

Discovery & classification

Also known as 2021 D1

Named

Sources