© NASA/Hubble Space Telescope

Mars enters retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Mars
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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 a planet in the outer solar system. Not drawn to scale.

2024–2025 apparition of Mars

06 Dec 2024 – Mars enters retrograde motion
12 Jan 2025 – Mars at perigee
15 Jan 2025 – Mars at opposition
23 Feb 2025 – Mars ends retrograde motion

Observing Mars

Mars enters retrograde motion as its 2024–2025 apparition gets underway, although it has already been visible for some weeks in the pre-dawn sky.

Its celestial coordinates as it enters retrograde motion will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 08h35m40s 21°32'N Cancer -0.6 12.2"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the morning sky, becoming accessible around 21:00, when it reaches an altitude of 8° above your eastern horizon. It will then reach its highest point in the sky at 03:29, 70° above your southern horizon. It will be lost to dawn twilight around 06:41, 44° above your western horizon.

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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 panels below show the month-by-month change in Mars' apparent size in coming weeks:

Mars
11 Oct 2024
Mars
08 Nov 2024
Mars
06 Dec 2024
Mars
03 Jan 2025
Mars
31 Jan 2025

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

Date Angular size Mag
27 Sep 20247.4”0.5
11 Oct 20248.0”0.4
25 Oct 20248.8”0.2
08 Nov 20249.8”-0.0
22 Nov 202410.9”-0.3
06 Dec 202412.2”-0.6
20 Dec 202413.5”-1.0
03 Jan 202514.4”-1.2
17 Jan 202514.5”-1.4
31 Jan 202513.7”-1.1
14 Feb 202512.3”-0.7
The sky on 06 December 2024
Sunrise
07:05
Sunset
16:25
Twilight ends
18:05
Twilight begins
05:25

5-day old moon
Waxing Crescent

37%

5 days old

Planets
Rise Culm. Set
Mercury 06:52 11:38 16:24
Venus 10:17 14:55 19:33
Moon 11:32 16:34 21:48
Mars 20:05 03:29 10:53
Jupiter 16:23 23:49 07:16
Saturn 12:16 17:49 23:21
All times shown in EST.

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

08 Dec 2022  –  Mars at opposition
12 Jan 2025  –  Mars at perigee
15 Jan 2025  –  Mars at opposition
19 Feb 2027  –  Mars at opposition

Image credit

© NASA/Hubble Space Telescope

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