Posted on by Nancy Atkinson

Supermoon This Weekend

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This weekend will provide the full Moon’s closest approach of the year to Earth. On Saturday, May 5, 2012 the Moon could appear as much as 14% bigger and 30% brighter than other full Moons of 2012, according to some calculations. Will you notice it? Not if you haven’t really been paying attention, or have a reference point to compare it to other full Moons. And it certainly won’t have any adverse effects on Earth, as this closest approach happens every year — just a fact of orbital mechanics. But perhaps a great way to celebrate Cinco de Mayo is to spend the evening gazing at the Moon!


Every month, as the Moon circles the Earth in its elongated orbit, its distance from the Earth varies. This weekend, the Moon is reaching what’s known as its perigee, the closest point to Earth in its orbit. It will be about 356,953 kilometers (221,802 miles) from Earth on Saturday. Apogee — when the Moon is farthest away — varies, but is around 405,000 km (252,000 miles) away.

What is most interesting is that the timing of the perigee and full Moon is really, really close: The full moon occurs at 03:34 UTC on May 6 (11:34 p.m. EDT on May 5 )eastern and perigee follows at 03:35 UTC (11:35 p.m. EDT)

David Morrison, from NASA says “supermoon” is not an astronomical term and he confirms a supermoon has no effect on Earth, and that the change in size is hardly noticeable to the average person. If you miss it, the Moon will be very nearly as close at the next full Moon, and very nearly as close as it was at the last full Moon.

But even better is that two weeks after the “supermoon” on May 5th, the Moon will be at apogee as it lines up in front of the Sun for an amazing annular eclipse on May 20th. An annular eclipse occurs when the Sun and Moon are exactly in line, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the outline of the Moon.

If you’re a photographer, take a picture of the Moon and send it to us. If we get a some good images, we’ll share them. Join our Flickr group, or send us your images by email (this means you’re giving us permission to post them). Please explain a little about it such as when you took it, the equipment you used, etc.

Here’s a video NASA put out about the Supermoon:

17 Replies to “Supermoon This Weekend”

  1. Dear Nancy, if you don’t mind.. I have question:
    In what years we have the biggest supermoon, which poin that we can define one supermoon event is bigger that another supermoon event in the past. Is that the size of the moon photo we take, the closest perigee distance, or what?

    I read news about supermoon on March 19, 2011. They say it’s the biggest supermoon for the last 18 years. Then I am confused, what poin we use to compare one supermoon to another supermoon.

    Thank you in advance.

    1. These events happen when a full moon coincides with the moon’s closest approach to Earth, but they don’t usually line up exactly. Sometimes the full moon misses the perigee by a several hours or a day, but sometimes they coincide almost perfectly.

      1. Thank you very much for the reply Grimbold. But with all due respect, it’s not that.. what I would like to know is when the biggest supermoon event ever recorded. Then, what poin or perimeter we can use to compare one supermoon event to another supermoon event. For example, which bigger 2011 supermoon or this 2012 supermoon, how can we know that.. what poin or perimeter we can use to compare them, between the two (or more) different supermoon event.

  2. Hahah , the doomsdayers are this time not claiming doom after the last Supermoon fiasco to produce anything threatening.

  3. I did some calculations last time and it is surprising that the Sun actually has a 179 times bigger force on Earth than the Moon. However the tidal forces are 2.1 bigger from the Moon than from the Sun.

    But people ignore the big mass that has an even more tidal force on Earth, and that is Earth itself.
    A whopping 17,888,518 times bigger than the Moon!

    1. I’m not sure the Earth can be said to have a “tidal force” on the Earth 😛

      2. it is not the gravitational force on a body that causes the tides. it is the gravitational gradient from one side of the earth to the other caused by a body at a distance. the sun’s effect on the tides are much less than the moon even though the total gravitational force is stronger. to prove this, use the equation above for and compare the delta of the force for the sun: use 1AU minus the radius of the earth and 1AU plus the radius of the earth. and repeat similarly for the moon. that will tell you the NET TIDAL force as apposed to the NET GRAVITATION force. Consequently you will notice that the tidal force of the earth on itself is 0 by performing the same calculation. you will also find that the closer and more massive the bodies the greater the effect (just look at Io and Europa)

      3. Yes for static point of view the gravitational gradient of Earth in itself will be constant because it moves with Earth’s frame. But it is really there and not zero.

        I don’t think your explanation if 1 AU+ and – Earth radius explains the tidal action. Because that would indicate that a continuous stream of water moves in the direction of the Moon.

      4. rest assured my explination is correct I am a rocket scientist. the tides do always fallow the moon. they are actually pulled slightly ahead of the moon. this process is actually causing the moon to speed up and drift away from the earth at a rate of about 2cm per year and consequently is causing the earths rotation to slow

  4. One wonders where the actual gravitational barycenter or node(s) will be at closest approach? Where will the moon be at fullest and closest, or directly overhead, on 03:34 UTC, May 6? 3:34 hrs east of Iceland, right?

    1. That event is not until June 5 or 6, (depending on your location on the planet.)

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