Jupiter

by Dominic Ford, Editor
Last updated: 24 Mar 2020

The planets of the solar system:
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune


Jupiter is currently an early evening object. From Fairfield, it is visible in the evening sky, becoming accessible around 18:24 (EDT), 25° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 20:40, 33° above your southern horizon. It will continue to be observable until around 00:58, when it sinks below 7° above your south-western horizon.

19 Aug 2021  –  Jupiter at opposition
26 Sep 2022  –  Jupiter at opposition
03 Nov 2023  –  Jupiter at opposition
07 Dec 2024  –  Jupiter at opposition
Jupiter

Jupiter, as seen by Cassini when it passed the planet on its way to Saturn. Image courtesy of NASA.

Jupiter is the fifth planet from the Sun, orbiting at a distance of 5.20 AU once every 11.86 years.

It is the solar system's largest and most massive planet, with 2.5 times the mass of all the other planets combined, and over 300 times that of the Earth. Its radius is over 10 times that of the Earth, but despite this, it rotates on its axis at phenomenal speed, completing one revolution every 9.9 hours.

Apparitions of Jupiter

The table below lists apparitions of Jupiter around the year 2021, computed from NASA's DE430 planetary ephemeris. To show events around other years, use the control below.

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Apparitions of Jupiter around 2021

Date Event Declination Angular size
Date Event Declination Angular size
28 Oct 2011 21:34 EDTJupiter at opposition11°49'N48.6"
02 Dec 2012 20:37 ESTJupiter at opposition21°19'N47.4"
05 Jan 2014 16:04 ESTJupiter at opposition22°41'N45.8"
06 Feb 2015 13:12 ESTJupiter at opposition16°31'N44.4"
08 Mar 2016 05:49 ESTJupiter at opposition6°04'N43.5"
07 Apr 2017 17:31 EDTJupiter at opposition5°36'S43.3"
08 May 2018 20:31 EDTJupiter at opposition16°00'S43.8"
10 Jun 2019 11:20 EDTJupiter at opposition22°25'S45.0"
14 Jul 2020 03:50 EDTJupiter at opposition21°57'S46.6"
19 Aug 2021 20:20 EDTJupiter at opposition13°38'S48.0"
26 Sep 2022 15:25 EDTJupiter at opposition0°08'S48.8"
03 Nov 2023 00:55 EDTJupiter at opposition13°31'N48.4"
07 Dec 2024 15:50 ESTJupiter at opposition22°01'N47.1"
10 Jan 2026 03:34 ESTJupiter at opposition22°14'N45.6"
10 Feb 2027 19:21 ESTJupiter at opposition15°16'N44.2"
12 Mar 2028 11:29 EDTJupiter at opposition4°29'N43.4"
11 Apr 2029 23:57 EDTJupiter at opposition7°09'S43.3"
13 May 2030 07:25 EDTJupiter at opposition17°11'S44.0"
15 Jun 2031 05:12 EDTJupiter at opposition22°49'S45.2"

Composition

Jupiter is a gas giant planet, composed mostly of hydrogen and helium. It does not have a solid surface and is comprised almost entirely of gas, though it may have a small solid core at its center.

Within this gaseous atmosphere there are thick clouds of tiny solid crystals, predominantly of ammonia. It is these clouds which make Jupiter opaque and determine its visual appearance.

These clouds are highly varied in color, meaning that Jupiter's disk has the greatest color contrasts of any of the planets. The pale-colored bright zones represent up-wellings of warm material, and the clouds tops of these zones are at higher altitude than those of the darker belts that separate them.

The dark belts appear to comprise of cooler sinking material, and it is believed that their deep red color stems from the interaction of the Sun's ultraviolet light with molecules dredged up from deeper within Jupiter's atmosphere by convection currents. While chemists refer to these molecules as chromophores, this is merely a generic term for any brightly colored compound, and the precise chemical composition of the chromophores present in Jupiter's atmosphere is not well understood.

The planet's rapid rotation drives weather systems which mean these rising and sinking regions predominate at alternate latitudes, in much the same way that the Earth's trade winds form. This creates Jupiter's familiar striped sequence of bands.

The two centre-most dark belts, closest to the equator, should be immediately apparent in even moderately poor seeing conditions. These are the North Equatorial Belt (NEB) and the South Equatorial Belt (SEB). On the southern edge of the SEB lies the famous Great Red Spot (GRS) which, when is readily apparent even in poor conditions.

Observing Jupiter

Jupiter's large angular size of up to 55" is rivalled only by Venus, and makes its disk quite apparent even through a modest pair of binoculars.

Its rapid rotation, however, makes long-exposure imaging tricky. Modern image-stacking software such as AutoStakkert not only use lucky imaging – selecting frames from long video sequences with the best atmospheric conditions – but also correct for the fact that the planet may have rotated over the course of the observation.

Finding Jupiter

Jupiter comes to opposition once every 399 days – its synodic period.

Where it lies in the sky affects how easily it can be observed from the northern or southern hemispheres, and because, by definition, it lies almost directly opposite the Sun at opposition, there is a close relationship between the time of year when Jupiter comes to opposition, and how well placed it is for observation.

When Jupiter comes to opposition in the northern summer months, the Sun is high in the northern sky, which places the opposite side of the eclipic plane in the southern sky. This means that Jupiter is poorly placed for observation from the northern hemisphere when at opposition in the summer.

Conversely, if Jupiter is at opposition in December, it is sure to be high in the northern sky.

The chart below shows the time of year of all of Jupiter's oppositions between the years 2000 and 2120, together with the declination that Jupiter will have at the time, measured on the vertical axis.

A chart of the time of day when Jupiter rises and sets on any given day of the year can be found here . A chart of Jupiter's path relative to the background stars can be found here.

NORAD ID COSPAR ID Name Launch date Flight ended Owner
NORAD ID COSPAR ID Name Launch date Flight ended Owner
5860 1972-012A PIONEER 10 03 Mar 1972 United States
6421 1973-019A PIONEER 11 05 Apr 1973 United States
10271 1977-076A VOYAGER 2 19 Aug 1977 United States
10321 1977-084A VOYAGER 1 04 Sep 1977 United States
20842 1990-090B ULYSSES 05 Oct 1990 United States
28928 2006-001A NEW HORIZONS 19 Jan 2006 United States

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