Jupiter ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed


Objects: Jupiter

1998 apparition of Jupiter

17 Jul 1998 – Jupiter enters retrograde motion
15 Sep 1998 – Jupiter at perigee
15 Sep 1998 – Jupiter at opposition
13 Nov 1998 – Jupiter ends retrograde motion

Jupiter will reach the end of its retrograde motion, ending its westward movement through the constellations and returning to more usual eastward motion instead. This reversal of direction is a phenomenon that all the solar system's outer planets periodically undergo, a few months after they pass opposition.

The retrograde motion is caused by the Earth's own motion around the Sun. As the Earth circles the Sun, our perspective changes, and this causes the apparent positions of objects to move from side-to-side in the sky with a one-year period. This nodding motion is super-imposed on the planet's long-term eastward motion through the constellations.

The diagram below illustrates this. The grey dashed arrow shows the Earth's sight-line to the planet, and the diagram on the right shows the planet's apparently movement across the sky as seen from the Earth:


The retrograde motion of a planet in the outer solar system. Not drawn to scale.

Observing Jupiter

Jupiter leaves retrograde motion as its 1998 apparition comes to an end, although it will remain visible for some weeks in the dusk sky.

As retrograde motion ends, it will be visible in the evening sky, becoming accessible around 17:06 (PST), 36° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 19:38, 49° above your southern horizon. It will continue to be observable until around 00:43, when it sinks below 7° above your western horizon.

Over the following weeks, Jupiter will reach its highest point in the sky four minutes earlier each night, gradually disappearing into evening twilight.

As it leaves retrograde motion, its celestial coordinates will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Jupiter 23h18m40s 5°59'S Aquarius -2.7 43.5"

The coordinates above are given in J2000.0.

The sky on 11 Jan 2026

The sky on 11 January 2026
Sunrise
06:56
Sunset
17:01
Twilight ends
18:30
Twilight begins
05:27


Waning Crescent

35%

23 days old

Planets
Rise Culm. Set
Mercury 06:40 11:33 16:26
Venus 07:06 12:04 17:02
Moon 00:54 06:18 11:36
Mars 06:59 11:56 16:53
Jupiter 16:42 23:49 06:57
Saturn 10:23 16:16 22:10
All times shown in PST.

Source

The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

13 Nov 1998  –  Jupiter ends retrograde motion
24 Aug 1999  –  Jupiter enters retrograde motion
23 Oct 1999  –  Jupiter at opposition
20 Dec 1999  –  Jupiter ends retrograde motion

Image credit

© NASA/Cassini

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