These next several evenings – November 14, 15 and 16 – highlight the moon and Mars coming quite close together on the sky’s dome. Look first for the moon, and you can’t miss the red planet Mars, which shines more brilliantly than a 1st-magnitude star all month long. For us in North America, the moon will swing closest to Mars for the month on the evening of November 15.
Of course, the moon and Mars are not truly close together in space, but more or less reside on the same line of sight. At present, the moon is about 250,000 miles (400,000 km) away from us, whereas Mars lies about 330 times the moon’s distance from Earth. Click here to know the moon’s present phase and present distance from Earth, and click here to know Mars’ present distance from Earth in astronomical units (sun-Earth distance).
After the moon and Mars first pop out at dusk or nightfall, watch for the brilliant twosome to move westward across the sky during the evening hours. They’ll finally set in the west quite late at night, very possibly after your bedtime. Click here for a recommended almanac that’ll give you the moon’s and Mars’ setting times in your sky.
Although the moon and Mars appear to travel westward in Earth’s sky due to the Earth rotating on its axis from west to east, the moon and Mars are actually traveling eastward relative to the background stars of the zodiac. Our moon only takes 27 1/3 days to travel full circle in front of the constellations of the zodiac, but it takes Mars some 1.88 Earth-years to do likewise. For that reason, the moon laps Mars once every month in Earth’s sky.
According to AstroPixels.com, the moon will swing one degree (two moon-diameters) south of Mars on November 16, at 04:16 Universal Time. At U.S. time zones, that’s November 15, at 23:16 (11:16 p.m.) EST, 22:16 (10:16 p.m.) CST, 21:16 (9:16 p.m.) MST, 20:16 (8:16 p.m.) PST, 19:16 (7:16 p.m.) AKST and 18:16 (6:16 p.m.) HST.
When an almanac tells you that the moon comes to within so many degrees of a planet or star, it usually means as viewed from the center of the Earth. But as viewed from different places on the Earth’s surface, the moon may appear closer – or farther away – from Mars (or a given star), due to a phenomenon known as lunar parallax. At more northerly latitudes, the moon will appear to swing father away from Mars; yet, from more southerly latitudes, the moon will appear to swing closer to Mars.
In fact, if you were at just the right spot in the far southern tip of South America (Argentina and Chile), you could actually watch the moon occult (pass in front of) Mars on the night of November 15-16. For instance, from Chile Chico, Chile, the moon will occult (cover over) Mars on November 16, 2018, with Mars disappearing behind the dark side of the moon at 2:22 a.m. local time and reappearing on the moon’s lit side at 3:09 a.m. local time.
Bottom line: Enjoy the celestial spectacle in mid-November 2018, as the waxing moon and the red planet Mars couple up in the evening sky.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.