Mars enters retrograde motion

Dominic Ford, Editor
From the Outer Planets feed


Objects: Mars

1960–1961 apparition of Mars

20 Nov 1960 – Mars enters retrograde motion
24 Dec 1960 – Mars at perigee
30 Dec 1960 – Mars at opposition
05 Feb 1961 – Mars ends retrograde motion

Mars will enter retrograde motion, halting its usual eastward movement through the constellations, and turning to move westwards instead. This reversal of direction is a phenomenon that all the solar system's outer planets periodically undergo, a few months before they reach 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:

04 Nov 1960
11.5"
02 Dec 1960
14.2"
30 Dec 1960
15.4"
27 Jan 1961
13.0"
24 Feb 1961
9.9"

Observing Mars

Mars enters retrograde motion as its 1960–1961 apparition gets underway, although it has already been visible for some weeks in the pre-dawn sky.

As retrograde motion starts, it will be visible in the morning sky, becoming accessible around 20:53, when it reaches an altitude of 8° above your north-eastern horizon. It will then reach its highest point in the sky at 03:18, 79° above your southern horizon. It will be lost to dawn twilight around 06:12, 50° above your western horizon.

Over the following weeks, Mars will reach its highest point in the sky four minutes earlier each night, gradually becoming visible in the evening sky, as well as the pre-dawn sky, as it approaches opposition.

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

Date Right ascension Declination Angular size Magnitude
21 Oct 196006h59m40s23°29'N10.4”-0.2
04 Nov 196007h16m30s23°34'N11.5”-0.5
18 Nov 196007h24m10s23°56'N12.9”-0.8
02 Dec 196007h20m30s24°44'N14.2”-1.1
16 Dec 196007h05m00s25°50'N15.2”-1.4
30 Dec 196006h41m30s26°47'N15.4”-1.5
13 Jan 196106h18m50s27°11'N14.5”-1.2
27 Jan 196106h05m00s27°08'N13.0”-0.8
10 Feb 196106h02m50s26°52'N11.4”-0.4
24 Feb 196106h10m50s26°32'N9.9”-0.0
10 Mar 196106h26m50s26°06'N8.7”0.3

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

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 07h24m20s 24°02'N Gemini -0.8 13.1"

The coordinates above are given in J2000.0.

The sky on 31 Jan 2026

The sky on 31 January 2026
Sunrise
06:47
Sunset
17:20
Twilight ends
18:46
Twilight begins
05:21


Waxing Gibbous

98%

13 days old

Planets
Rise Culm. Set
Mercury 07:20 12:35 17:50
Venus 07:14 12:29 17:45
Moon 16:14 23:34 06:45
Mars 06:36 11:43 16:50
Jupiter 15:11 22:20 05:28
Saturn 09:09 15:04 21:00
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

20 Nov 1960  –  Mars enters retrograde motion
24 Dec 1960  –  Mars at perigee
30 Dec 1960  –  Mars at opposition
05 Feb 1961  –  Mars ends retrograde motion

Image credit

© NASA/Hubble Space Telescope

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