2018 will have three new moon supermoons in a row, which are defined as new or full moons at or near their closest to Earth for that particular month. 2018’s new supermoons fall on June 13, July 13 and August 11. Thus this next new moon on July 13 is a supermoon; in fact, it’s the closest and largest of the three.
New moon falls precisely on July 13, 2018, at 2:48 UTC; that is July 12 at 10:48 p.m. EDT, 9:48 p.m. CDT and so on.
You don’t typically see a new moon, not even a new supermoon, but Earth’s oceans will feel it. This extra-close new moon will combine with the gravitational pull of the sun to give rise to wide-ranging spring tides – tides that are extra high and extra low – in the few days following July 13.
Plus, a few people in Earth’s Southern Hemisphere will glimpse this July 13 new moon. At least, they’ll see the new moon silhouette, or part of it, during a partial solar eclipse on July 13. A month from now, people at high latitudes in the Northern Hemisphere will be able to view the new supermoon during a second partial solar eclipse, on August 11.
Two weeks from July 13 – on Friday, July 27, 2018 – we’ll have the smallest full moon of the year. The year’s smallest full moon is sometimes called a micro-moon or mini-moon. It’s the opposite of a supermoon. A micro-moon always happens within a fortnight of the year’s closest new moon.
The July 13 new moon comes especially close to Earth because it’s the year’s closest coincidence of a new moon with a lunar perigee.
New moon: July 13, 2018, at 2:48 UTC
Lunar perigee: July 13, 2018, at 8:28 UTC
But this is not the closest supermoon. Remember, supermoons can be new or full moons. At a distance of 222,097 miles (357,431 km), the July 13 perigee is only the 2nd-closest of this year’s 14 lunar perigees. The year’s closest perigee of 221,559 miles (356,565 km) accompanied the full moon supermoon on the night of January 1-2, 2018. Thus that full moon was 2018’s closest supermoon.
Now here’s an older term for the close alignment of the July 13 new moon with lunar perigee: some will call it a perigean new moon.
One fortnight after the perigean new moon, it’ll be a apogean full moon on July 27, 2018, that features the year’s closest coincidence of full moon with lunar apogee. At a distance of 252,415 miles (406,223 km), this will be the 2nd-farthest of this year’s 13 apogees. The apogean full moon on July 27 will be about 30,000 miles or 50,000 km farther away than the perigean full moon of July 13.
Full moon: July 27, 2018, at 20:20 UTC
Lunar apogee: July 27, 2018, at 5:44 UTC
The year’s farthest apogee – 252,565 miles (406,464 km) – took place on January 15, 2018, or one fortnight after the year’s closest perigee in early January 2018.
Don’t you just love the orderliness of the heavens?
Bottom line: The closest new supermoon of 2018 comes on July 13.
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.