Tonight's Long Night Moon is closest in 15 years
The full moon that rises over Baltimore tonight is the last before the winter solstice, which makes it the Long Night Moon. Some also call it the Moon Before Yule.
But this full moon is even more notable for the fact that it will be the closest Earth's only natural satellite has come to its mother planet in 15 years, and the nearest until 2016. If there were an easy way to compare it side-by-side with a more average full moon, it would even appear visibly nearer - and larger. Maybe you'll notice anyway. It's said to be as much as 14 percent wider and 30 percent brighter than your run-of-the-mill full moon.
This event is called "perigee," the moon's closest approach to the Earth for the month as it moves along in its 28-day elliptical orbit of the Earth. In this case, that translates to about 221,559 miles at 5 p.m. this afternoon. That's about 25 minutes after moonrise in Baltimore. If the clouds clear off soon enough, we may actually get a look at it.
The Maryland Science Center will be offering even closer views of the moon, 5:30 to 9 this evening, weather permitting, through their Crosby Ramsey Memorial Observatory telescope, where it is Stargazing Friday. No charge. For information, call 410 685-5225.
For the period from the year 1750 through 2125, the nearest perigee was 221,441 miles, on Jan. 4, 1912. The farthest apogee will be 252,724 miles, on Feb. 3, 2125. So during tonight's perigee the moon will be just 118 miles farther away than the closest perigee of that entire 375-year period. Cool!
This perigee also comes just a few hours after the moon is precisely full - at 11:38 EST this morning. And when the full moon and perigee coincide, we can anticipate unusually high tides, although wind and weather conditions may blunt the effect. You can track the tides in real time here.