When, Where and How to See the Planets in the 2018 Night Sky


This is a spectacular year for Mars. On July 31 at 3:50 a.m. EDT, the planet will come closer to Earth than at any other time since its historically close approach of August 2003. Its distance from Earth at that moment will be 35.78 million miles (57.59 million kilometers). Not until September 2035 will it come so close again.

Shining like a “star” with a yellow-orange hue, Mars can vary considerably in brightness. It will appear in the mornings from Jan. 1 through July 26, and evenings from July 27 through Dec. 31. It will appear brightest between July 21 to Aug. 3.

Mars will start the year in the morning sky, rising just before 3 a.m. in the constellation Libra, just west of the planet Jupiter, and shining only 1/20 as bright as Jupiter. At that time, Mars will be 181.4 million miles (292 million km) away, but it will be approaching Earth at an average of 687,000 miles (1.10 million km) a day and consequently will be getting slowly brighter.

After April 1, its increase in brightness will start becoming more noticeable: By April 13 it will reach zero magnitude while cruising through the constellation Sagittarius, shining low in the southeast sky during the predawn hours. (See this Space.com guide to understand how the brightness of night sky objects are measured.) On June 9, now in the constellation Capricornus, it will rival Sirius, the brightest of all stars in Earth’s sky (besides the sun, of course), rising above the east-southeast horizon before midnight.

So bright does Mars become that between July 7 and Sept. 6 it will supplant mighty Jupiter as the second brightest planet and become the third brightest object in the nighttime sky (next to the moon and Venus). It arrives at opposition to the sun (meaning it is on the opposite side of the Earth as the sun) on July 27. Mars will still be in Capricornus, visible from dusk to dawn and shining at an eye-popping magnitude of minus 2.8 — four times brighter than the star Sirius, and more than twice as bright as Jupiter!

From July 27 through Dec. 31, Mars will appear in the evenings. After reaching this pinnacle, Mars will recede from Earth and gradually become dimmer through the balance of the year. By New Year’s Eve, it’s shining at a still-respectable magnitude of +0.5 in western Pisces, southeast of the Circlet asterism, crossing the meridian at dusk and setting in the west soon after 11 p.m. local time. On the mornings of Jan. 6 and 7, watch as Mars slides less than a half degree to the south of Jupiter. On the evening of Dec. 7, Neptune will be only about a quarter of a degree west of Mars, providing a good benchmark for sighting this dim, blue world in binoculars. Neptune will appear only about 1/1,500 as bright as Mars.

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