© NASA/Hubble Space Telescope

Mars ends retrograde motion

Dominic Ford, Editor
From the Outer Planets feed

Objects: Mars
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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.

1980 apparition of Mars

16 Jan 1980 – Mars enters retrograde motion
25 Feb 1980 – Mars at opposition
26 Feb 1980 – Mars at perigee
06 Apr 1980 – Mars ends retrograde motion

Observing Mars

Mars leaves retrograde motion as its 1980 apparition comes to an end, although it will remain visible for some weeks in the dusk sky.

Its celestial coordinates as it leaves retrograde motion will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 09h57m50s 15°39'N Leo -0.4 11.2"

The coordinates above are given in J2000.0.

From Fairfield , it will be visible in the evening sky, becoming accessible around 18:49 (EDT), 53° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 20:48, 64° above your southern horizon. It will continue to be observable until around 02:54, when it sinks below 9° 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 disappearing into evening twilight.

The panels below show the month-by-month change in Mars' apparent size in coming weeks, as it recedes from the Earth:

Mars
10 Feb 1980
Mars
09 Mar 1980
Mars
06 Apr 1980
Mars
04 May 1980
Mars
01 Jun 1980

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

Date Angular size Mag
27 Jan 198012.1”-0.6
10 Feb 198013.3”-1.0
24 Feb 198013.8”-1.2
09 Mar 198013.5”-1.0
23 Mar 198012.5”-0.7
06 Apr 198011.2”-0.4
20 Apr 198010.0”-0.0
04 May 19808.9”0.2
18 May 19808.1”0.5
01 Jun 19807.3”0.7
15 Jun 19806.7”0.8

The sky on 28 Mar 2024

The sky on 28 March 2024
Sunrise
06:40
Sunset
19:13
Twilight ends
20:47
Twilight begins
05:06

18-day old moon
Waning Gibbous

87%

18 days old

Planets
Rise Culm. Set
Mercury 07:08 13:57 20:46
Venus 06:08 11:53 17:38
Moon 21:47 02:58 08:00
Mars 05:29 10:52 16:16
Jupiter 08:21 15:22 22:23
Saturn 05:52 11:26 17:00
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

06 Apr 1980  –  Mars ends retrograde motion
20 Feb 1982  –  Mars enters retrograde motion
31 Mar 1982  –  Mars at opposition
05 Apr 1982  –  Mars at perigee

Image credit

© NASA/Hubble Space Telescope

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41.14°N
73.26°W
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