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Comet 21P/Giacobini-Zinner

Comet 21P/Giacobini-Zinner is currently in the constellation of Leo. The current Right Ascension of Comet 21P/Giacobini-Zinner is 11h 24m 11s and the Declination is -06° 03’ 16” (topocentric coordinates computed for the selected location: Greenwich, United Kingdom [change]). The current estimated magnitude of Comet 21P/Giacobini-Zinner is 23.18 (JPL).

Summary of key facts about Comet 21P/Giacobini-Zinner [tip: you can also create a Quick Access page for this data if you access it frequently and would like to have a simpler view]:

11h 24m 11s
-06° 03’ 16”
  • 21P/Giacobini-Zinner is above the horizon from Greenwich, United Kingdom [change].
  • It is visible looking in the West direction at an altitude of 0° above the horizon.
  • Given its current magnitude, 21P/Giacobini-Zinner is visible only through long exposure photography.
  • See also 21P/Giacobini-Zinner rise and set times.
  • Go to interactive sky chart

If you need to access this information frequently for your observations, you can create a simple customized Quick Access page, so that you can easily bookmark it in your browser favorites or add a shortcut to your mobile phones' home screen.

Additional information about Comet 21P/Giacobini-Zinner available on TheSkyLive:

Available Resources

Comet 21P/Giacobini-Zinner Position and Finder Charts

Below we provide Comet 21P/Giacobini-Zinner finder charts showing where the object is right now in the sky with respect to the brightest stars. The first finder chart has a field of view of 50 degrees, while the second one has a field of view of 10 degrees. Click on each finder chart to access a full screen interactive Online Planetarium.

Map showing Comet 21P/Giacobini-Zinner in Leo on May, 08 2021
Field of view: 50x30 degrees
View fullscreen
Map showing Comet 21P/Giacobini-Zinner in Leo on May, 08 2021
Field of view: 10x6 degrees
View fullscreen
 = visible to the naked eye
 = binocular, brighter than 10th magnitude
= current altitude ≥ 30°   = current altitude < 30°   = below the horizon
Location: Greenwich, United Kingdom [change]

Higher precision deep sky finder chart, 60 arcmin wide, showing where Comet 21P/Giacobini-Zinner is right now. Click on the image to see a more detailed fullscreen tracker view.

RA: 11h 24m 11s
Dec: -06° 03’ 16”
Deep sky finder chart for Comet 21P/Giacobini-Zinner
Field of view: 60x40 arcmins
View fullscreen

Also check out Where is Comet 21P/Giacobini-Zinner?, a page that provides all the information needed to find Comet 21P/Giacobini-Zinner in the sky and additional links to sky charts.

Comet 21P/Giacobini-Zinner Distance from Earth

The distance of Comet 21P/Giacobini-Zinner from Earth is currently 774,836,634 kilometers, equivalent to 5.179463 Astronomical Units. Light takes 43 minutes and 4.5768 seconds to travel from Comet 21P/Giacobini-Zinner and arrive to us.

43 minutes and 4.5768 seconds

The following chart shows the distance of Comet 21P/Giacobini-Zinner from Earth as a function of time. In the chart the distance data is measured in Astronomical Units and sampled with an interval of 1 day.

Distance of Comet 21P/Giacobini-Zinner from Earth between January 2013 and December 2100

The value of the reported distance might be somewhat inaccurate around the times of closest approach for objects passing extremely close to Earth. The value of the distance of 21P/Giacobini-Zinner from Earth is also available as a real time updated value in the Live Position and Data Tracker.

Closest approach of Comet 21P/Giacobini-Zinner to Earth

Between January 2013 and December 2100, the closest approach of Comet 21P/Giacobini-Zinner to Earth happens on Fri Oct 28 2078 at a distance of 0.255783 Astronomical Units, or 38,264,657 kilometers:

Fri Oct 28 2078

NOTE: values for the closest approach are computed with a sampling interval of 1 day.

Comet 21P/Giacobini-Zinner brightness

The current visual magnitude of Comet 21P/Giacobini-Zinner is 23.18.


The observed magnitude and coma diameter values are derived from the Comet Observers Database by averaging the values reported in recent observations (more recent than 4 days), when available. The Estimated Magnitude comes from the JPL Horizons ephemerides service and might be inaccurate given the highly dynamic and unpredictable behavior of comets. When available, please refer to the Observed Magnitude value and consider the Estimated Magnitude as a directional indication. We acknowledge with thanks the comet observations from the COBS Comet Observation Database contributed by observers worldwide and used in this table to report recent comet observations.

The following chart is the predicted light curve (visual magnitude as a function of time) of Comet 21P/Giacobini-Zinner, according to the most recent ephemerides data. Magnitude data is sampled with a 2 days interval and there might be inaccuracies for objects changing brightness very rapidly during the course of a few days. For comets there could be large discrepancies between the observed and predicted brightness because of their highly dynamic behaviour.

Predicted magnitude of Comet 21P/Giacobini-Zinner between January 2013 and December 2100

Comet 21P/Giacobini-Zinner rise and set times

Location: Greenwich, United Kingdom [change]
Latitude: 51° 28’ 47” N
Longitude: 0° 00’ 00” E
Timezone: Europe/London

Today's Comet 21P/Giacobini-Zinner rise, transit and set times from Greenwich, United Kingdom [change] are the following (all times relative to the local timezone Europe/London):

Azimuth: 96.0°
Max altitude: 32.5°
Azimuth: 263.9°

The rise and set times are defined as the time at which the upper limb of Comet 21P/Giacobini-Zinner touches the horizon, considering the effect of the atmospheric refraction. As the atmospheric conditions cannot be modeled precisely the times reported here should be considered correct with an approximation of few minutes.

Comet 21P/Giacobini-Zinner Orbital Elements

The following table lists the orbital elements of Comet 21P/Giacobini-Zinner at epoch 05 November 2017 00:00 UTC (JD: 2458063.5). Source: JPL Small-Body Database

Element Symbol Value
Orbit eccentricity e 0.71046678
Orbit inclination i 32.00303376°
Perihelion distance q 1.01349375 AU
151,616,507 km
Aphelion distance Q 5.98738696 AU
895,700,342 km
Semi-major axis a 3.50044036 AU
523,658,425 km
Orbital period period 6.5500 years
2,392.1172 days
Date of perihelion transit Tp 2018-Sep-10 06:22:16
2,458,371.7655 JD
Next perihelion transit 2025-Mar-29 09:11
2,460,763.8826 JD
Argument of perihelion peri 172.80915964581°
Longitude of the ascending node node 195.40514495049°
Mean anomaly M 313.60780403717°
Mean motion n 0.15049430°/day

Visualization of Comet 21P/Giacobini-Zinner Orbit

This 3d orbit diagram is a feature of our 3D Solar System Simulator and shows the orbit of Comet 21P/Giacobini-Zinner with respect of the Sun and the orbits of the major planets. The position of Comet 21P/Giacobini-Zinner and the planets along their orbits in this diagram accurately represents the current configuration of the objects in the Solar System. This is an experimental feature and it requires a WebGL enabled browser. Please provide us feedback!

Orbit Diagram of Comet 21P/Giacobini-Zinner
View Comet 21P/Giacobini-Zinner in the 3D Solar System Simulator

Comet 21P/Giacobini-Zinner 15 Days Ephemeris

The following table lists the ephemerides of Comet 21P/Giacobini-Zinner computed for the past and next 7 days, with a 24 hours interval. Click on each row of the table to locate Comet 21P/Giacobini-Zinner in our Online Planetarium at the chosen date.

Date Right AscensionR.A. DeclinationDec. MagnitudeMag Constellation
2021 May 01 11h 25m 56s -06° 35’ 21” 23.14 Leo
2021 May 02 11h 25m 40s -06° 30’ 38” 23.14 Leo
2021 May 03 11h 25m 23s -06° 25’ 58” 23.15 Leo
2021 May 04 11h 25m 08s -06° 21’ 21” 23.15 Leo
2021 May 05 11h 24m 52s -06° 16’ 50” 23.16 Leo
2021 May 06 11h 24m 38s -06° 12’ 20” 23.17 Leo
2021 May 07 11h 24m 24s -06° 07’ 55” 23.17 Leo
2021 May 08 11h 24m 11s -06° 03’ 34” 23.18 Leo
2021 May 09 11h 24m 00s -05° 59’ 17” 23.19 Leo
2021 May 10 11h 23m 48s -05° 55’ 05” 23.20 Leo
2021 May 11 11h 23m 38s -05° 50’ 57” 23.20 Leo
2021 May 12 11h 23m 27s -05° 46’ 53” 23.21 Leo
2021 May 13 11h 23m 17s -05° 42’ 52” 23.22 Leo
2021 May 14 11h 23m 08s -05° 38’ 57” 23.22 Leo