“Supermoon” Can Be Seen In Your Backyard Saturday Night May 5th, 14% Bigger And 30% Brighter
At 8:40 p.m. Pacific Time on Saturday, according to the Griffith Observatory Sky Report, the moon will be at its closest point in its orbit to the Earth this year. (Accounting for the time zone difference, European moon-watchers will see it Sunday.) To be precise, Earth and moon will be just 221,801 miles apart — more than 17,000 miles closer than average.
NASA’s Science News calculates the moon’s appearance Saturday will be “as much as 14% bigger and 30% brighter than other full moons of 2012.”
Some call what’s known as a perigee full moon a “supermoon,” which may or may not be accurate. EarthSky gives a lengthy explanation of the term and concludes with this: “Bottom line: The full moon of May 5 (or 6), 2012, is the closest and largest full moon of this year. Some will call it a supermoon.”
But that doesn’t mean you’ll be able to notice the difference. “There are no rulers floating in the sky to measure lunar diameters,” the NASA story says. “Hanging high overhead with no reference points to provide a sense of scale, one full moon can seem much like any other.”
On this Skip and I agree. The nighttime sky can be much fun.
Thanks, Skip.
Here you go, you moonies. Going to get even better and brighter.
Due to the moon’s elliptical orbit about the earth, there will be a great moon around perigee [closest point to earth] on May 5, 6, or 7 [Greenwich Time]. According to the Nautical Almanac, the moon’s apparent semidiameter will be 16.7 minutes of arc on those dates. The moon will also be full on the 6th [again, that’s GMT]. Great Moon is when perigee and full moon come at the same time.
By contrast, around new moon on Apr 21, 22, 23, the moon was at apogee [furthest away]and had a semidiameter of 14.7 minutes of arc.
The Nautical Almanac notes the moon and sun’s semidiameter for every day of the year so this number can be added or subtracted to a sextant observation to get the exact location of the center of the orb. The sun’s semidiameter was greatest this year at 16.3′, and is currently near minimum at 15.8′.
http://science.nasa.gov/media/medialibrary/2011/03/16/movie_strip.jpg
While you’re out, here’s something else you can do. Look north and find the Big Dipper. You can’t miss it. The two bright stars at the end of the bowl, the pointers, always point to the North Star, Polaris, whose distance in degrees above the Northern horizon will be your latitude.
Now follow the curve of the Dipper’s handle across the sky and to your east you’ll see that arc hit a a bright reddish star, Arcturus, the brightest star in the constellation Bootes, the Charioteer. Continue that arc to the SE and you’ll find another bright star, Spica, in the constellation of Virgo the Virgin. This year you’ll get an extra treat. Near Spica is a an even brighter star: the planet Saturn.
Now everybody, grab your sextants, star charts, and Captain Jack’s current star almanic and the next stary night we’ll have some fun.
skip.