© NASA/Hubble Space Telescope

Mars at opposition

Dominic Ford, Editor
From the Outer Planets feed

Objects: Mars
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The sky at

Mars will reach opposition, when it lies opposite to the Sun in the sky. Lying in the constellation Taurus, it will be visible for much of the night, reaching its highest point in the sky around midnight local time.

From Seattle, it will be visible between 16:59 and 07:10. It will become accessible around 16:59, when it rises to an altitude of 7° above your north-eastern horizon. It will reach its highest point in the sky at 00:05, 67° above your southern horizon. It will become inaccessible around 07:10 when it sinks below 7° above your north-western horizon.

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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

A close approach to the Earth

At around the same time that Mars passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest.

This happens because when Mars lies opposite to the Sun in the sky, the Earth passes between Mars and the Sun. The solar system is lined up with Mars and the Earth on the same side of the Sun, as shown by the configuration labelled perigee in the diagram below:


When a planet is at opposition, the solar system is aligned such that the planet lies on the same side of the Sun as the Earth. At this time, the planet makes its perigee, or closest approach to the Earth. Not drawn to scale.

The panels below show a comparison of the apparent size of Mars when seen at opposition in 2022, and when it is most distant from the Earth at solar conjunction.

Also shown is the full range of different sizes it can appear at opposition, due to the slightly oval shape of Mars' orbit. It appears largest when it reaches opposition around late August, and significantly smaller when it reaches opposition around late February.

Mars
Mars at closest opposition
Mars
Mars at 2022 opposition
Mars
Mars at furthest opposition
Mars
Mars at solar conjunction

Mars: our close neighbor

Of all the planets, Mars shows the greatest variation in its apparent size and brightness. Its angular size varies by a factor of more than seven, between 25.69" and 3.49".

This comes about because it neighbors the Earth in the solar system, orbiting the Sun at a distance of about 1.5 times the Earth's distance from the Sun. This means that its distance from the Earth varies greatly, between 0.36 AU and 2.68 AU. depending whether it lies next to, or opposite to, the Earth in its orbit.

The geometry of Mars' orbit is such that it spends much longer periods of time at large distances from the Earth than it does close to us, which provides added incentive to observe it in the weeks around opposition. Whenever it passes opposition, every two years, Mars appears large and bright for only a few weeks. The panels below show the month-by-month change in Mars' apparent size:

Mars
12 Oct 2022
Mars
09 Nov 2022
Mars
07 Dec 2022
Mars
04 Jan 2023
Mars
01 Feb 2023

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

Date Angular size Mag
28 Sep 202211.8”-0.6
12 Oct 202213.1”-0.8
26 Oct 202214.6”-1.1
09 Nov 202216.1”-1.4
23 Nov 202217.1”-1.7
07 Dec 202217.0”-1.9
21 Dec 202215.9”-1.5
04 Jan 202314.1”-1.1
18 Jan 202312.2”-0.6
01 Feb 202310.6”-0.2
15 Feb 20239.2”0.1

This data is also available in the form of a graph of the angular size of Mars here, and a graph of its brightness here.

Observing Mars

At opposition, Mars is visible for much of the night. When it lies opposite to the Sun in the sky, this means that it rises at around the time the Sun sets, and it sets at around the time the Sun rises. It reaches its highest point in the sky at around midnight local time.

But even when it is at its closest point to the Earth, it is not possible to distinguish it as more than a star-like point of light without the aid of a telescope.

A chart of the path of Mars across the sky in 2022 can be found here, and a chart of its rising and setting times here.

At the moment of opposition, Mars will lie at a distance of 0.55 AU, and its disk will measure 17.0 arcsec in diameter, shining at magnitude -1.9. Its celestial coordinates at the moment it passes opposition will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 04h57m10s 24°57'N Taurus -1.9 17.0"

The coordinates above are given in J2000.0.

Over the weeks following its opposition, Mars will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.

The sky on 07 December 2022
Sunrise
07:43
Sunset
16:19
Twilight ends
18:11
Twilight begins
05:51

14-day old moon
Waning Gibbous

99%

14 days old

Planets
Rise Culm. Set
Mercury 09:10 13:07 17:04
Venus 08:42 12:50 16:57
Moon 15:17 --:-- 07:30
Mars 15:59 00:06 08:13
Jupiter 13:06 19:02 00:58
Saturn 11:46 16:37 21:27
All times shown in PST.

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

07 Dec 2022  –  Mars at opposition
12 Jan 2025  –  Mars at perigee
15 Jan 2025  –  Mars at opposition
19 Feb 2027  –  Mars at opposition

Image credit

© NASA/Hubble Space Telescope

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