The summer is about to get pretty super for all of you skygazers out there. You can expect three supermoons over the next three months.
Have you ever wondered why some full moons look larger than others? Scientists call it a perigee moon. It happens when a full moon occurs on the side of the moon closest to the earth. These full moons look bigger and brighter than others because the "perigee" side of the moon is 50,000 km closer to the earth than the other side.
Supermoons occur on July 12, August 10 and September 9 this summer.
On August 10th it becomes full during the same hour as perigee—arguably making it an extra-super Moon."
Supermoons aren't all that rare. In fact, they usually happen about every 13 months. There were three perigee moons in a row last year, too! But, sometimes you won't notice a supermoon because of clouds or pollution.
In practice, it's not always easy to tell the difference between a super moon and an ordinary full Moon. A 30% difference in brightness can easily be masked by clouds and haze. Also, there are no rulers floating in the sky to measure lunar diameters. Hanging high overhead with no reference points to provide a sense of scale, one full Moon looks about the same size as any other.
So, step out of the house this summer and gaze into the night sky and impress your friends with your knowledge of perigee moons!