© 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 Mars. Not drawn to scale.

1954 apparition of Mars

23 May 1954 – Mars enters retrograde motion
24 Jun 1954 – Mars at opposition
02 Jul 1954 – Mars at perigee
29 Jul 1954 – Mars ends retrograde motion

Observing Mars

Mars enters retrograde motion as its 1954 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 18h40m30s 25°16'S Sagittarius -1.6 17.1"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the morning sky, becoming accessible around 00:04, when it reaches an altitude of 7° above your south-eastern horizon. It will then reach its highest point in the sky at 03:32, 23° above your southern horizon. It will be lost to dawn twilight around 05:09, 19° above your south-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
28 Mar 1954
Mars
25 Apr 1954
Mars
23 May 1954
Mars
20 Jun 1954
Mars
18 Jul 1954

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

Date Angular size Mag
14 Mar 19548.3”0.3
28 Mar 19549.5”0.0
11 Apr 195410.9”-0.3
25 Apr 195412.6”-0.7
09 May 195414.7”-1.1
23 May 195417.1”-1.6
06 Jun 195419.5”-2.0
20 Jun 195421.3”-2.4
04 Jul 195421.9”-2.4
18 Jul 195421.0”-2.2
01 Aug 195419.2”-1.9

The sky on 25 Jun 2024

The sky on 25 June 2024
Sunrise
05:19
Sunset
20:29
Twilight ends
22:38
Twilight begins
03:10

19-day old moon
Waning Gibbous

74%

19 days old

Planets
Rise Culm. Set
Mercury 06:13 13:50 21:26
Venus 05:45 13:19 20:53
Moon 23:04 03:58 09:00
Mars 02:19 09:14 16:10
Jupiter 03:35 10:56 18:16
Saturn 00:18 05:59 11:41
All times shown in EDT.

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

23 May 1954  –  Mars enters retrograde motion
24 Jun 1954  –  Mars at opposition
02 Jul 1954  –  Mars at perigee
29 Jul 1954  –  Mars ends retrograde motion

Image credit

© NASA/Hubble Space Telescope

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