© 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.

2022–2023 apparition of Mars

30 Oct 2022 – Mars enters retrograde motion
30 Nov 2022 – Mars at perigee
07 Dec 2022 – Mars at opposition
12 Jan 2023 – Mars ends retrograde motion

Observing Mars

Mars enters retrograde motion as its 2022–2023 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 05h39m20s 23°47'N Taurus -1.2 15.0"

The coordinates above are given in J2000.0.

From Seattle , it will be visible in the morning sky, becoming accessible around 21:17, when it reaches an altitude of 7° above your north-eastern horizon. It will then reach its highest point in the sky at 04:17, 66° above your southern horizon. It will be lost to dawn twilight around 07:32, 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
04 Sep 2022
Mars
02 Oct 2022
Mars
30 Oct 2022
Mars
27 Nov 2022
Mars
25 Dec 2022

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

Date Angular size Mag
21 Aug 20229.2”-0.0
04 Sep 202210.0”-0.2
18 Sep 202210.9”-0.4
02 Oct 202212.1”-0.6
16 Oct 202213.4”-0.9
30 Oct 202215.0”-1.2
13 Nov 202216.4”-1.5
27 Nov 202217.2”-1.8
11 Dec 202216.9”-1.8
25 Dec 202215.5”-1.4
08 Jan 202313.6”-1.0
The sky on 30 October 2022
Sunrise
07:52
Sunset
17:56
Twilight ends
19:40
Twilight begins
06:04

5-day old moon
Waxing Crescent

36%

5 days old

Planets
Rise Culm. Set
Mercury 07:20 12:35 17:49
Venus 08:00 13:01 18:03
Moon 14:14 18:08 22:07
Mars 20:17 04:17 12:17
Jupiter 16:39 22:35 04:31
Saturn 15:12 20:00 00:47
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

30 Nov 2022  –  Mars at perigee
07 Dec 2022  –  Mars at opposition
12 Jan 2025  –  Mars at perigee

Image credit

© NASA/Hubble Space Telescope

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