© NASA/Hubble Space Telescope

Mars at opposition

Fri, 27 Jul 2018 at01:07 EDT(516 days away)
05:07 UTC

Dominic Ford, Editor
From the Outer Planets feed

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The sky at

Mars will be well placed for observation, in the constellation Capricornus. It will be visible for much of the night, reaching its highest point in the sky at around midnight local time.

From Newark (click to change), it will be visible between 21:36 and 04:36. It will become accessible at around 21:36, when it rises 7° above your south-eastern horizon, and then reach its highest point in the sky at 01:08, 23° above your southern horizon. It will become inaccessible at around 04:36 when it sinks to 8° above your south-western horizon.

Mars opposite the Sun

This optimal positioning occurs when Mars is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.

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 the Sun in the sky, the solar system is lined up so that Mars, the Earth and the Sun form a straight line with the Earth in the middle, on the same side of the Sun as Mars.

The time of Mars's perigee is an especially good time to observe it, since it neighbors the Earth in the solar system and has the greatest variation of all of the planets in its distance from the Earth. This in turn leads to a large variation in its apparent size and brightness.

Mars's distance from the Earth can vary between 0.36 AU and 2.68 AU, meaning that its disk varies in diameter between 25.68" and 3.49".

When it passes opposition, Mars glides past the Earth rather quickly, and so only appears large and bright in the sky for a few weeks. A graph of the angular size of Mars at this opposition is available here, and a graph of its brightness is available here.

On this occasion, Mars will lie at a distance of 0.39 AU, and its disk will measure 24.3 arcsec in diameter, shining at magnitude -2.8. Even at its closest approach to the Earth, however, it is not possible to distinguish it as more than a star-like point of light without the aid of a telescope.

Mars in coming weeks

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.

A chart of the path of Mars across the sky in 2018 can be found here, and a chart of its rising and setting times here.

The position of Mars at the moment it passes opposition will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
Mars 20h31m30s -25°33' Capricornus -2.8 24.3"

The coordinates above are given in J2000.0.

The sky on 27 July 2018
Sunrise: 05:47
Sunset: 20:16
Twilight
from 03:54
until 22:10

14-day old moon
Age of Moon:
14 days

All times shown in EDT.
Rise Culm. Set
Mercury 07:33 14:11 20:50
Venus 09:36 15:55 22:14
Moon 20:22 00:31 05:21
Mars 20:37 01:08 05:35
Jupiter 14:09 19:19 00:33
Saturn 18:09 22:49 03:32

Source

The circumstances of this event were computed using the DE405 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

27 Jul 2018, 01:07 EDTMars at opposition
02 Sep 2019, 07:01 EDTMars at solar conjunction
13 Oct 2020, 19:19 EDTMars at opposition
08 Oct 2021, 00:20 EDTMars at solar conjunction

Image credit

© NASA/Hubble Space Telescope

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