The comet 21P/Giacobini-Zinner

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From Ashburn , 21P/Giacobini-Zinner is not readily observable since it is very close to the Sun, at a separation of only 11° from it.

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Name 21P/Giacobini-Zinner
Object Type Comet
Current Position
Constellation:Crater
Magnitude:24.06 (V) [2]
Absolute mag (H):9.40 [2]
Slope parameter (n):5.84 [2]
Right ascension:11h25m [1]
Declination:-08°03' [1]
Distance:6.34 AU
52.73 lightmin [1]
Orbital Elements [1]
Semi-major axis:3.50 AU
Eccentricity:0.710710
Inclination:32.02°
Longitude ascending node:195.36°
Argument of perihelion:172.85°
Epoch of elements:22 September 2020
Mean Anomaly at epoch:111.97°
Derived quantities
Perihelion:1.01 AU
Aphelion:5.98 AU
Orbital period:6.54 years
Visibility from Ashburn

All times shown in Ashburn local time.

Events
24 Mar 2025  –  21P/Giacobini-Zinner at perihelion
Additional sources

The position of this comet was calculated from orbital elements published by the Minor Planet Center (MPC).

We estimate the brightnesses of comets from magnitude parameters published by the BAA Comet Section, where these are available. These are computed from the observations they receive from amateur astronomers.

Comets are intrinsically highly unpredictable objects, since their brightness depends on the scattering of sunlight from dust particles in the comet's coma and tail. This dust is continually streaming away from the comet's nucleus, and its density at any particular time is governed by the rate of sublimation of the ice in the comet's nucleus, as it is heated by the Sun's rays. It also depends on the amount of dust that is mixed in with that ice. This is very difficult to predict in advance, and can be highly variable even between successive apparitions of the same comet.

In consequence, while the future positions of comets are usually known with a high degree of confidence, their future brightnesses are not. For most comets, we do not publish any magnitude estimates at all. For the few comets where we do make estimates, we generally prefer the BAA's magnitude parameters to those published by the Minor Planet Center, since they are typically updated more often.

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39.04°N
77.49°W
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