Largest full moon of 2009 visible on January 10

Make sure to check it out tonight, or tomorrow night depending on where you live.

If skies are clear Saturday, go out at sunset and look for the giant moon rising in the east. It will be the biggest and brightest one of 2009, sure to wow even seasoned observers.

Earth, the moon and the sun are all bound together by gravity, which keeps us going around the sun and keeps the moon going around us as it goes through phases. The moon makes a trip around Earth every 29.5 days.

But the orbit is not a perfect circle. One portion is about 31,000 miles (50,000 km) closer to our planet than the farthest part, so the moon's apparent size in the sky changes. Saturday night (Jan. 10) the moon will be at perigee, the closest point to us on this orbit.

It will appear about 14 percent bigger in our sky and 30 percent brighter than some other full moons during 2009, according to NASA. (A similar setup occurred in December, making that month's full moon the largest of 2008.)

The article annoyingly fails to tell us whether the full moon this month is larger or smaller than the one we just had a month ago. It's a bit odd that the article doesn't compare two moons that are one month apart simply because they happen to be in different years. If the new year started in February then it would have told us which one is larger.

A quick look at Stellarium shows them to be more or less the same though.