© NASA/Cassini

Saturn ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Saturn
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Saturn 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.

1961 apparition of Saturn

09 May 1961 – Saturn enters retrograde motion
19 Jul 1961 – Saturn at opposition
27 Sep 1961 – Saturn ends retrograde motion

Observing Saturn

Saturn leaves retrograde motion as its 1961 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
Saturn 19h42m40s 21°35'S Sagittarius 0.2 17.2"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the evening sky, becoming accessible around 19:12 (EDT) as the dusk sky fades, 25° above your southern horizon. It will then reach its highest point in the sky at 20:07, 27° above your southern horizon. It will continue to be observable until around 23:39, when it sinks below 10° above your south-western horizon.

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

The sky on 10 May 2021
Sunrise
05:38
Sunset
20:02
Twilight ends
21:50
Twilight begins
03:46

28-day old moon
Waning Crescent

0%

28 days old

Planets
Rise Culm. Set
Mercury 06:35 14:12 21:49
Venus 06:18 13:38 20:58
Moon 05:17 12:06 19:03
Mars 08:46 16:23 00:00
Jupiter 02:29 07:47 13:06
Saturn 01:44 06:43 11:43
All times shown in EDT.

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 Jul 1961  –  Saturn at opposition
31 Jul 1962  –  Saturn at opposition
13 Aug 1963  –  Saturn at opposition
24 Aug 1964  –  Saturn at opposition

Image credit

© NASA/Cassini

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41.14°N
73.26°W
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