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Comet Near-Earth

Giacobini-Zinner

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21P/Giacobini-Zinner

Where is it now

Distance from Sun
4.734 AU
True anomaly
153.14°
Distance from Earth
5.567 AU
As of
11 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 — 0.998 AU from the Sun Earth Giacobini-Zinner — 4.734 AU from the Sun Giacobini-Zinner
Seen from above the ecliptic, north up, to scale. Grid: Earth's orbit in blue. Giacobini-Zinner is 5.567 AU from Earth today (46.3 light-minutes).

In the sky

Right ascension
11h 05m 23s
Declination
-10° 01′ 57″
Constellation
Crater
Distance from Earth
5.57 AU
Elongation from the Sun
30.78° — near the Sun — look low at dusk or dawn

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
3.5 AU
Eccentricity
0.7105
Inclination
32°
Orbital period
6.55 years
Perihelion
1.013 AU
Aphelion
5.987 AU
Longitude of ascending node
195.4°
Argument of periapsis
172.81°
Epoch · J2000
2458070.5
Orbit class · JFc
Jupiter-family comet (P < 20 y)
Earth MOID · 6.9 LD
0.0178 AU
Tisserand (Jupiter)
2.465

Orbit quality

Orbit very well determined (uncertainty code 0).

Observations used
1,993
Data arc
13.48 years
First observed
1 May 2011
Last observed
21 October 2024
Residual RMS
0.52 ″
Solution · Shantanu Naidu
23 November 2025

Physical properties

Mean radius
1.00 km

Visual & observation

Absolute magnitude (H)
13.2
Total magnitude M₁ · K₁ 8.3
13.2

Discovery & classification

Discovered by
Giacobini, M.
Discovery date
20 December 1900
Discovery site
Nice Observatory, France

Also known as 21P · 1900 III · 1900c · 1913 V · 1913e · 1926 VI · 1926e · 1933 III

Near-Earth Object Named

Close approaches 17 on record

Flyby geometry
Ecliptic flyby of Giacobini-Zinner at 2105-09-22 07:40 UTC Top-down view of the ecliptic, Earth at the centre, for the 2105-09-22 07:40 UTC close approach of Giacobini-Zinner. Catalogue miss distance 66.6 LD · 2.56 × 10⁷ km. The curve is the geocentric path from 2105-09-19 to 2105-09-25, with a mark at UTC midnights and an arrow for the direction of motion. The circle is the Moon’s mean orbit; the Moon is plotted at closest approach. A ray shows the Sun’s direction. The labelled distance is the full separation. The drawn radius is the part that lies in the ecliptic plane. The path is approximate: a two-body Kepler propagation of the catalogue orbital elements, not a numerical integration. The Moon’s position is approximate. The inset is a heliocentric view and is approximate. approximate Sun 66.6 LD · 2.56 × 10⁷ km 2105-09-22 07:40 UTC Earth Moon Heliocentric, approximate

Top-down view of the ecliptic, Earth at the centre, for the 2105-09-22 07:40 UTC close approach of Giacobini-Zinner. Catalogue miss distance 66.6 LD · 2.56 × 10⁷ km. The curve is the geocentric path from 2105-09-19 to 2105-09-25, with a mark at UTC midnights and an arrow for the direction of motion. The circle is the Moon’s mean orbit; the Moon is plotted at closest approach. A ray shows the Sun’s direction. The labelled distance is the full separation. The drawn radius is the part that lies in the ecliptic plane. The path is approximate: a two-body Kepler propagation of the catalogue orbital elements, not a numerical integration. The Moon’s position is approximate. The inset is a heliocentric view and is approximate.

When (UTC) Body Distance Lunar distances Relative speed
2029-02-14 04:42:00 Jupiter 0.3638 AU 141.6 LD 8.2 km/s
2029-02-14 04:42:00 Juptr 0.3638 AU 141.6 LD 8.2 km/s
2040-04-15 16:27:00 Juptr 1.8189 AU 707.9 LD 10.3 km/s
2076-08-10 22:38:00 Juptr 0.2389 AU 93.0 LD 8.7 km/s
2076-08-10 22:38:00 Jupiter 0.2389 AU 93.0 LD 8.7 km/s
2087-08-06 10:26:00 Juptr 1.2223 AU 475.7 LD 8.8 km/s
2105-09-22 07:40:00 Earth 0.1713 AU 66.6 LD 19.2 km/s
2124-01-19 02:13:00 Juptr 0.6207 AU 241.6 LD 9.6 km/s
2135-05-09 19:58:00 Juptr 0.7964 AU 309.9 LD 7.7 km/s
2158-10-18 04:45:00 Earth 0.1663 AU 64.7 LD 21 km/s

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

Sources