Mars ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed


Objects: Mars

1956 apparition of Mars

10 Aug 1956 – Mars enters retrograde motion
06 Sep 1956 – Mars at perigee
10 Sep 1956 – Mars at opposition
10 Oct 1956 – Mars ends retrograde motion

Mars 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 Mars. Not drawn to scale.

The panels below show the month-by-month change in Mars' apparent size in coming weeks, as it recedes from the Earth:

16 Jul 1956
17.5"
13 Aug 1956
22.4"
10 Sep 1956
24.7"
08 Oct 1956
20.9"
05 Nov 1956
15.5"

Observing Mars

Mars leaves retrograde motion as its 1956 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 17:42 (PST), 18° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 21:39, 46° above your southern horizon. It will continue to be observable until around 02:31, when it sinks below 7° above your western horizon.

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

The table below lists Mars' angular size and brightness at two-week intervals throughout its apparition:

Date Right ascension Declination Angular size Magnitude
02 Jul 195623h12m00s9°34'S15.3”-1.2
16 Jul 195623h31m50s8°14'S17.5”-1.6
30 Jul 195623h44m40s7°36'S20.0”-2.0
13 Aug 195623h48m10s7°50'S22.4”-2.3
27 Aug 195623h41m40s8°46'S24.3”-2.7
10 Sep 195623h28m00s9°54'S24.7”-2.9
24 Sep 195623h13m50s10°28'S23.4”-2.6
08 Oct 195623h06m20s10°03'S20.9”-2.2
22 Oct 195623h08m20s8°39'S18.1”-1.7
05 Nov 195623h19m00s6°30'S15.5”-1.3
19 Nov 195623h36m20s3°49'S13.3”-0.9

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

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 23h06m00s 9°56'S Aquarius -2.1 20.6"

The coordinates above are given in J2000.0.

The sky on 30 Jan 2026

The sky on 30 January 2026
Sunrise
06:48
Sunset
17:19
Twilight ends
18:46
Twilight begins
05:22


Waxing Gibbous

98%

12 days old

Planets
Rise Culm. Set
Mercury 07:18 12:32 17:45
Venus 07:14 12:28 17:43
Moon 15:01 22:35 06:01
Mars 06:37 11:44 16:50
Jupiter 15:16 22:24 05:33
Saturn 09:12 15:08 21:03
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

10 Oct 1956  –  Mars ends retrograde motion
10 Oct 1958  –  Mars enters retrograde motion
08 Nov 1958  –  Mars at perigee
16 Nov 1958  –  Mars at opposition

Image credit

© NASA/Hubble Space Telescope

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