Mars ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed


Objects: Mars

2106 apparition of Mars

13 Jan 2106 – Mars enters retrograde motion
22 Feb 2106 – Mars at opposition
22 Feb 2106 – Mars at perigee
04 Apr 2106 – 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:

28 Dec 2105
9.7"
25 Jan 2106
12.2"
22 Feb 2106
13.8"
22 Mar 2106
12.4"
19 Apr 2106
9.9"

Observing Mars

Mars leaves retrograde motion as its 2106 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 19:30 (PST), 55° above your eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 21:42, 73° above your southern horizon. It will continue to be observable until around 03:43, when it sinks below 9° 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
14 Dec 210510h38m20s11°26'N8.6”0.3
28 Dec 210510h51m50s10°34'N9.7”0.0
11 Jan 210610h58m00s10°26'N10.9”-0.3
25 Jan 210610h55m20s11°13'N12.2”-0.7
08 Feb 210610h42m40s12°50'N13.4”-1.0
22 Feb 210610h22m50s14°50'N13.8”-1.2
08 Mar 210610h02m10s16°27'N13.4”-1.0
22 Mar 210609h47m40s17°11'N12.4”-0.7
05 Apr 210609h42m40s17°00'N11.1”-0.3
19 Apr 210609h47m00s16°03'N9.9”-0.0
03 May 210609h58m40s14°31'N8.8”0.3

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

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 09h42m40s 17°03'N Leo -0.4 11.2"

The coordinates above are given in J2000.0.

The sky on 12 Jan 2026

The sky on 12 January 2026
Sunrise
06:55
Sunset
17:02
Twilight ends
18:31
Twilight begins
05:27


Waning Crescent

29%

23 days old

Planets
Rise Culm. Set
Mercury 06:43 11:36 16:29
Venus 07:07 12:05 17:04
Moon 01:52 07:02 12:06
Mars 06:58 11:56 16:53
Jupiter 16:37 23:45 06:52
Saturn 10:19 16:13 22:06
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

04 Apr 2106  –  Mars ends retrograde motion
18 Feb 2108  –  Mars enters retrograde motion
28 Mar 2108  –  Mars at opposition
01 Apr 2108  –  Mars at perigee

Image credit

© NASA/Hubble Space Telescope

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