© 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 a planet in the outer solar system. Not drawn to scale.

2027 apparition of Mars

10 Jan 2027 – Mars enters retrograde motion
19 Feb 2027 – Mars at opposition
19 Feb 2027 – Mars at perigee
01 Apr 2027 – Mars ends retrograde motion

Observing Mars

Mars leaves retrograde motion as its 2027 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 09h36m00s 17°40'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 19:41 (EDT), 53° above your south-eastern horizon, as dusk fades to darkness. It will then reach its highest point in the sky at 21:50, 66° above your southern horizon. It will continue to be observable until around 04:02, when it sinks below 8° above your western horizon.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

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:

04 Feb 2027
04 Mar 2027
01 Apr 2027
29 Apr 2027
27 May 2027

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

Date Angular size Mag
21 Jan 202712.2”-0.6
04 Feb 202713.3”-1.0
18 Feb 202713.8”-1.2
04 Mar 202713.5”-1.0
18 Mar 202712.4”-0.7
01 Apr 202711.2”-0.4
15 Apr 20279.9”-0.0
29 Apr 20278.8”0.3
13 May 20278.0”0.5
27 May 20277.2”0.7
10 Jun 20276.6”0.9
The sky on 01 April 2027
Twilight ends
Twilight begins

24-day old moon
Waning Crescent


24 days old

Rise Culm. Set
Mercury 05:58 11:37 17:16
Venus 05:23 10:52 16:21
Moon 04:03 09:00 14:02
Mars 14:42 21:50 04:58
Jupiter 14:26 21:30 04:35
Saturn 07:00 13:18 19:37
All times shown in EDT.


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

19 Feb 2027  –  Mars at perigee
25 Mar 2029  –  Mars at opposition
29 Mar 2029  –  Mars at perigee
04 May 2031  –  Mars at opposition

Image credit

© NASA/Hubble Space Telescope






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