Tonight – on the night of July 26, 2018 – Mars comes to opposition in our sky for the first time since May 22, 2016. At opposition, our planet Earth, the 3rd planet from the sun, passes in between the sun and Mars, the 4th planet from the sun. Any time our planet Earth, in its smaller and swifter orbit, passes in between the sun and a superior planet (planet orbiting the sun outside Earth’s orbit), that planet is said to be at opposition.
Mars comes to opposition on July 27 around 5 UTC. At United States times zones, that places the time of opposition at 1 EDT, 12 midnight CDT – and on July 26 at 11 p.m. MDT, 10 p.m. PDT, 9 p.m. Alaskan Time and 7 p.m. Hawaiian Time.
Opposition is an extra-special event because it’s at or near opposition that Mars comes closest to Earth for the year, and that Mars, in turn, shines at its brightest best in Earth’s sky. Moreover, any planet at opposition shines all night long. Now opposite the sun, Mars rises in the east around sunset, climbs to its highest point in the sky at midnight, and sets in the west around sunrise.
Not all Mars’ oppositions are equal, though, and this is Mars’ brightest appearance in our sky in nearly 15 years! Mars is even outshining the king planet Jupiter, which is most often the fourth-brightest celestial object to light up the sky (after the sun, moon and Venus). But this year, in 2018, Mars replaces Jupiter as the fourth-brightest heavenly body from about July 7 to September 7, 2018. You can’t miss Mars right now! Even tonight’s drenching moonlight won’t be able to wash the red planet from the nighttime sky.
Mars alternates between good and bad years for viewing in our sky, and 2016 counts as a very good year because it is an opposition year. In the alternate years, Mars stays on the far side of the sun from Earth and is relatively faint and inconspicuous in our sky.
Extra-close oppositions of Mars (less than 37 million miles or 60 km) recur in periods of 15 to 17 years. The last extra-close Martian opposition happened on August 28, 2003, and the next one will occur on September 15, 2035. Extra-close oppositions happen when we go between Mars and the sun around the time Mars is near perihelion – its closest point to the sun. Makes sense, right?
This year’s opposition doesn’t bring Mars as close as it was in August 2003. But it’s a good opposition, and Mars is very bright in our sky.
An extra-far opposition (over 62 million miles or 100 km) last took place on March 3, 2012, when Mars was near aphelion – its farthest point from the sun. Extra-far oppositions also recur in periods of 15 to 17 years, and the next one will be forthcoming on February 19, 2027. As a basis of comparison, the 2018 opposition of Mars finds the planet about 28 million miles (45 million km) closer than extra-far opposition of 2012.
By the way, Mars comes closest to Earth some four days after opposition, on July 31, 2018. If Earth and Mars orbited the sun in perfect circles and on the same exact plane, Earth would come closest to Mars right at opposition. However, Mars always comes closest to Earth at the vicinity of opposition. The time interval between opposition and Mars’ nearest point to Earth is no greater than 8.5 days, and can be as little as 10 minutes.
Bottom line: July 2018 is the best time in nearly 15 years to see Mars. Earth passes between Mars and the sun on July 27, 2018 (the martian opposition). Earth and Mars will be closest on July 31, 2018.