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Comets » 

Comet 21P/Giacobini-Zinner

Above the horizon.  Rise: 5:59 | Tran: 12:00 | Set: 18:01
Alt: 28.72°   Az: 132.70°   Direction: South-East

Comet 21P/Giacobini-Zinner is in the constellation of Aquarius, at a distance of 310,981,661.0 kilometers from Earth. The current Right Ascension is 21h 46m 38s and the Declination is +00° 19’ 24” (apparent coordinates). The predicted magnitude of Comet 21P/Giacobini-Zinner is 15.25 (data provided by JPL Horizons).

Finder Charts

Map showing Comet 21P/Giacobini-Zinner in Aquarius on February, 16 2025. Field of view: 50x30 degrees
View interactive star map
Sky map showing Comet 21P/Giacobini-Zinner in Aquarius on February, 16 2025. Field of view: 15x9 degrees. View in interactive sky chart

High 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.

21P/Giacobini-Zinner
RA: 21h 45m 21s
Dec: +00° 12’ 24”
Deep sky finder chart for Comet 21P/Giacobini-Zinner. Field of view: 60x40 arcmins. View in deep sky object tracker

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.

Celestial Coordinates

Apparent

21h 46m 38s
+00° 19’ 24”
21h 19m 29s
19h 06m 07s

J2000

21h 45m 21s
+00° 12’ 24”

Additional Information

Aquarius
n/a
n/a
n/a
n/a
15.25

The observed values of Magnitude, Coma Diameter and Tail Length are derived from the most recent observation recorded at the Comet Observers Database. The value of Predicted Magnitude comes from the JPL Horizons ephemerides service and, in the case of comets, might be inaccurate given the highly dynamic and unpredictable behavior of these objects. When available, please refer to the Observed Magnitude value and consider the Predicted 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.

Rise and Set Times

Today's rise, transit and set times of Comet 21P/Giacobini-Zinner from Greenwich, UK (all times relative to the local timezone Europe/London):

Azimuth: 89.7°
Max altitude: 38.9°
Azimuth: 270.4°
  • 21P/Giacobini-Zinner is above the horizon from Greenwich, UK.
  • Right now it is placed in the South-East direction at an altitude of 28.72° above the horizon.
  • Given its current magnitude, 21P/Giacobini-Zinner is visible with the help of a telescope having an aperture of 20 inches (500mm) or more.
  • 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.

Distance from Earth

The distance of Comet 21P/Giacobini-Zinner from Earth is currently 310,981,661.0 kilometers, equivalent to 2.0787840064 Astronomical Units. Light takes 17m 17.323s to travel from Comet 21P/Giacobini-Zinner and arrive to us.

310,981,661.0
2.0787840064
17m 17.323s

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.

Chart of the distance of Comet 21P/Giacobini-Zinner from Earth in Astronomical Units (au)

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

Between 1 January 2000 and 31 December 2099, the closest approach of Comet 21P/Giacobini-Zinner to Earth happens on Sun Oct 30 2078 at a distance of 0.289030 Astronomical Units, or 43,238,333 kilometers:

Sun Oct 30 2078
43,238,333
0.289030

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

Light Curve

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.

Chart of the magnitude of Comet 21P/Giacobini-Zinner as a function of time

Orbital Elements

The following table lists the orbital elements of Comet 21P/Giacobini-Zinner at epoch 12 November 2017 00:00 UTC (JD: 2458070.5). Source: JPL Small-Body Database

Element Symbol Value
Orbit eccentricity e 0.71047048
Orbit inclination i 32.00259232°
Perihelion distance q 1.01344100 AU
151,608,616 km
Aphelion distance Q 5.98716470 AU
895,667,092 km
Semi-major axis a 3.50030285 AU
523,637,854 km
Orbital period period 6.5489 years
2,391.9762 days
Date of perihelion transit Tp 2018-Sep-10 06:22:53
2,458,371.7659 JD
Next perihelion transit 2025-Mar-29 05:48
2,460,763.7421 JD
Argument of perihelion peri 172.81248242749°
Longitude of the ascending node node 195.40448019669°
Mean anomaly M 314.65852733856°
Mean motion n 0.15050317°/day

Orbit Visualization

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

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. Apparent celestial coordinates are provided.

Date Right AscensionR.A. DeclinationDec. MagnitudeMag Constellation
2025 Feb 09 21h 17m 21s -00° 29’ 56” 15.45 Aquarius
2025 Feb 10 21h 21m 15s -00° 23’ 31” 15.42 Aquarius
2025 Feb 11 21h 25m 10s -00° 17’ 01” 15.39 Aquarius
2025 Feb 12 21h 29m 07s -00° 10’ 24” 15.37 Aquarius
2025 Feb 13 21h 33m 04s -00° 03’ 44” 15.34 Aquarius
2025 Feb 14 21h 37m 03s +00° 03’ 00” 15.31 Aquarius
2025 Feb 15 21h 41m 03s +00° 09’ 48” 15.29 Aquarius
2025 Feb 16 21h 45m 04s +00° 16’ 42” 15.26 Aquarius
2025 Feb 17 21h 49m 06s +00° 23’ 40” 15.24 Aquarius
2025 Feb 18 21h 53m 09s +00° 30’ 41” 15.21 Aquarius
2025 Feb 19 21h 57m 13s +00° 37’ 46” 15.19 Aquarius
2025 Feb 20 22h 01m 18s +00° 44’ 53” 15.16 Aquarius
2025 Feb 21 22h 05m 24s +00° 52’ 03” 15.14 Aquarius
2025 Feb 22 22h 09m 31s +00° 59’ 16” 15.12 Aquarius

Additional Resources