© NASA/Cassini

Saturn ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Saturn
Please wait
Loading 0/4
Click and drag to rotate
Mouse wheel to zoom in/out
Touch with mouse to dismiss
The sky at

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.

2021 apparition of Saturn

23 May 2021 – Saturn enters retrograde motion
01 Aug 2021 – Saturn at opposition
10 Oct 2021 – Saturn ends retrograde motion

Observing Saturn

Saturn leaves retrograde motion as its 2021 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 20h36m40s 19°25'S Capricornus 0.3 17.4"

The coordinates above are given in J2000.0.

From Seattle , it will be visible in the evening sky, becoming accessible around 19:07 (PDT), 20° above your southern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 20:28, 22° above your southern horizon. It will continue to be observable until around 23:38, when it sinks below 10° above your south-western horizon.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

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 October 2021
Sunrise
07:23
Sunset
18:31
Twilight ends
20:15
Twilight begins
05:39

4-day old moon
Waxing Crescent

32%

4 days old

Planets
Rise Culm. Set
Mercury 07:13 12:44 18:15
Venus 11:46 15:56 20:06
Moon 12:53 17:06 21:11
Mars 07:17 12:54 18:31
Jupiter 16:35 21:29 02:23
Saturn 15:55 20:28 01:01
All times shown in PDT.

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

01 Aug 2021  –  Saturn at opposition
14 Aug 2022  –  Saturn at opposition
27 Aug 2023  –  Saturn at opposition
07 Sep 2024  –  Saturn at opposition

Image credit

© NASA/Cassini

Share

Follow

Seattle

Latitude:
Longitude:
Timezone:

47.61°N
122.33°W
PDT

Color scheme