If tonight's full moon appears larger and more luminous than usual, it's not because you're loony or due for a new pair of glasses. The moon, you see, orbits Earth in an ellipse with one end closer to Earth than the other; tonight's full moon corresponds closely with the orbit's perigee, the closer end of that ellipse. (The more distant end of the ellipse is known as apogee.) What's more, tonight's perigee will bring the moon and Earth closer together than they have been at full moon since 1993, according to the Washington Post.
That means that tonight's moon will appear 14 percent larger and 30 percent brighter than the other 11 full moons this year. While the size of the moon can be difficult to gauge in the middle of the night sky, its luminosity should be more readily apparent: the nearby moon should light up the outdoors tonight "like a cosmic floodlamp," NASA says.
Hello and goodnight, moon.
Photo of perigee (left) and apogee (right) moon courtesy of Galileo Project/NASA