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.
1977–1978 apparition of Jupiter
| 24 Oct 1977 | – | Jupiter enters retrograde motion |
| 21 Dec 1977 | – | Jupiter at perigee |
| 22 Dec 1977 | – | Jupiter at opposition |
| 19 Feb 1978 | – | Jupiter ends retrograde motion |
Observing Jupiter
Jupiter leaves retrograde motion as its 1977–1978 apparition comes to an end, although it will remain visible for some weeks in the dusk sky.
Its celestial coordinates as it leaves retrograde motion will be:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| Jupiter | 05h44m10s | 23°17'N | Taurus | -2.5 | 41.4" |
The coordinates above are given in J2000.0.
From Columbus , it will be visible in the evening sky, becoming accessible around 18:31 (EDT), 62° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 20:17, 73° above your southern horizon. It will continue to be observable until around 02:55, when it sinks below 7° above your north-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.
The sky on 17 Jul 2024
| The sky on 17 July 2024 | ||||||||||||||||||||||||||||||||||
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84% 12 days old |
All times shown in EDT.
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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
| 19 Feb 1978 | – Jupiter ends retrograde motion |
| 25 Nov 1978 | – Jupiter enters retrograde motion |
| 24 Jan 1979 | – Jupiter at opposition |
| 25 Mar 1979 | – Jupiter ends retrograde motion |
Image credit
© NASA/Cassini