© 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.

2035 apparition of Mars

15 Aug 2035 – Mars enters retrograde motion
11 Sep 2035 – Mars at perigee
15 Sep 2035 – Mars at opposition
15 Oct 2035 – Mars ends retrograde motion

Observing Mars

Mars enters retrograde motion as its 2035 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 00h01m40s 6°09'S Pisces -2.2 21.8"

The coordinates above are given in J2000.0.

From Ashburn , it will be visible in the morning sky, becoming accessible around 22:39, when it reaches an altitude of 7° above your eastern horizon. It will then reach its highest point in the sky at 03:37, 44° above your southern horizon. It will be lost to dawn twilight around 06:02, 33° 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
20 Jun 2035
Mars
18 Jul 2035
Mars
15 Aug 2035
Mars
12 Sep 2035
Mars
10 Oct 2035

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

Date Angular size Mag
06 Jun 203511.6”-0.5
20 Jun 203513.1”-0.8
04 Jul 203514.9”-1.1
18 Jul 203517.0”-1.5
01 Aug 203519.4”-1.9
15 Aug 203521.8”-2.2
29 Aug 203523.9”-2.6
12 Sep 203524.6”-2.8
26 Sep 203523.6”-2.7
10 Oct 203521.3”-2.2
24 Oct 203518.5”-1.8

The sky on 15 Aug 2035

The sky on 15 August 2035
Sunrise
06:19
Sunset
20:04
Twilight ends
21:44
Twilight begins
04:39

12-day old moon
Waxing Gibbous

90%

12 days old

Planets
Rise Culm. Set
Mercury 08:18 14:40 21:02
Venus 06:27 13:20 20:13
Moon 17:48 22:55 04:04
Mars 21:54 03:37 09:20
Jupiter 23:45 06:43 13:41
Saturn 05:20 12:25 19:31
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

15 Aug 2035  –  Mars enters retrograde motion
11 Sep 2035  –  Mars at perigee
15 Sep 2035  –  Mars at opposition
15 Oct 2035  –  Mars ends retrograde motion

Image credit

© NASA/Hubble Space Telescope

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39.04°N
77.49°W
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