Bad Astronomy
The entire universe in blog form
June 23 2013 1:49 PM


Goodnight, Supermoon.
Goodnight, Supermoon. Click to hyperlunenate.

Photo by Tunç Tezel, used by permission

So, another “Supermoon” has come and gone, and as I expected there was a lot of talk about it online (and a lot of snark on Twitter, which was also expected). I did a few interviews about it as well for some radio stations (and CNN, which should air tonight at 7:15 p.m. EDT). While I still think this whole Supermoon thing is way, way overblown, it did get folks outside looking up, and I love to hear that!

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

I saw a lot of pictures taken of the Moon, many of which were really nice. I think the best I’ve seen, though, is the one above by my pal Tunç Tezel, showing the Moon setting behind the Temple of Athena, in the town of Assos in northwest Turkey, very close to the Aegean Sea. He used some mapping and sky-mapping software to find the best place to set up, so the Moon would set at the right position and angle to capture this gorgeous shot.


That’s pretty amazing! I like how we now have access to accurate maps and powerful enough computers such that calculating the necessary trigonometry is as simple as downloading the right software. It still took Tunç a lot of planning to get it right, and he only had one chance at this! Well, until the next full Moon, of course.

I want to take a moment to mention something else, too. Technically, there is a single moment when the Moon is most full, and that happened at 11:32 UTC (07:32 EDT) Sunday. Perigee, the moment when the Moon was closest to Earth, was about 20 minutes earlier, at 11:11 UTC. However, it’s not like suddenly the Moon was full at that moment, or suddenly closer at perigee. These things happen slowly over many hours.

So if you saw the Moon last night, Saturday, at midnight, say, it looked very much the same as it will Sunday night at midnight. The phase will be slightly different, but it won’t be that much farther from Earth than it was last night. The change in distance is far less than 1 percent (literally just a few hundred kilometers, a surprisingly small amount), so it’ll only be a tiny bit smaller, a difference completely invisible to the eye. Given that the “Supermoon” happened this morning, it kinda splits the difference between Saturday and Sunday.

When I was interviewed about all this, I talked about going out to see the Moon Sunday night, tonight, because of this. I honestly didn’t think there would be a lot of hype about it Saturday night, but obviously I was wrong. I was caught by surprise, so mea culpa. I should've realized, since it was closer to completely full Saturday night than Sunday. But in reality, it hardly matters. If you missed it last night, the Moon will still look very close to full, and still be big, silvery, and beautiful tonight.

If there’s one lesson from all of this, I’d say it’s that you should always take the opportunity to look at our Moon. It’s worth it.


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