Supermoon feast begins – it’s three in a row, baby!

Overnight tonight we’ll see the first of three supermoons in July, August and September. Credit: Gary Hershorn / Reuters

If the moon’s orbit were circular there’d be no such thing as ‘supermoons’, the occasional, extra-large full moons we see about once every 13 months. But circular orbits are exceedingly rare. Most celestial bodies dance about each other in ellipses. At one end of the ellipse, the two bodies are closest; at the other end, farthest.

The moon revolves around Earth in an elliptical orbit, passing through perigee (closest point to Earth) and apogee about once each month. When perigee occurs at full moon, we see a supermoon. Credit: Bob King

When the full moon coincides with its time of closest approach to Earth Рcalled perigee Рits disk can be up to 14% bigger and 30% brighter than typical full moons. In 2014 we get three consecutive perigee or supermoons in a row. The first occurs tomorrow morning July 12 at 3:28 a.m. CDT about 3 hours before the moment of full moon. Not a perfect match but close.

The next supermoons happen on August 10 (1 p.m. CDT) and September 8 (10:30 p.m.)

“Generally speaking, full moons occur near perigee every 13 months and 18 days, so it’s not all that unusual,” said Geoff Chester of the US Naval Observatory. “In fact, just last year there were three perigee Moons in a row, but only one was widely reported.”

The size difference between an apogee (foreground) and perigee or supermoon. Would that we could see them simultaneously to truly appreciate their different sizes. Credit: Tom Ruen

Supermoons get a lot of press because the word ‘super’ attached to anything these days naturally attracts attention.

While the phenomenon is very real, it’s also really hard to see because there are no rulers you can hold up to the sky to compare the size of one full moon to another. They ALL look big especially when the full moon’s near the horizon. That’s when the infamous¬†‘moon illusion’ kicks in and psychologically inflates the lunar disk up another notch.

Still, there’s every reason to go out and enjoy a full moon, super or not. The striking beauty of a moonrise, the curious mix of light and dark areas representing ancient crust (light) and titanic impact craters (dark) and the soft, yet stark illumination of the landscape where mystery abounds in every shadow. I could go on and on.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

16 thoughts on “Supermoon feast begins – it’s three in a row, baby!

  1. I don’t know where you are Bob, but here in NW WI the full Thundermoon is living up to its amazing name.
    Wow and best to you for summer.
    Jeannette

  2. Hey Bob,
    Do you know any good places around the duluth area where it’s dark and quiet that would be a good place to look at the moon?

    • Hi Lee,
      Come out to my house! Just kidding. You might consider the Western Waterfront Trail or Lester Park (maybe a little buggy). The soccer parking lot on Riley Road off Jean Duluth Road is often open on one end. I’ve been able to get in there recently.

  3. Tomorrow, a close bright big Moon, a triple conjunction of Venus, Mercury and Comet Jacques. I know that Jacques is faint but Venus should be a nice guide. Then fainter but maybe easier to see UQ4 Catalina. Catalina should fade rapidly through July.

  4. Bob,

    We had our telescopes down at the Canal Park (Duluth), we had over 150 people see the Moon, Saturn and Mars.

  5. I drove out into the country, saw Venus then pointed my big binoculars toward Comet Jacques. I believe that I got a glimpse of it but it was extremely faint.

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