August 11, 2014
The nighttime sky is always interesting to look at, but perhaps this week more than usual.
Image by Marco Langbroek
If you happened to watch the moonrise last night, you might have seen a cape flying out behind the giant moon. Well, not really, no cape, but last night’s moon was this year’s supermoon, and it did look bigger than usual–about 8 percent bigger. The above image shows the potential difference in size.
What’s a supermoon? A supermoon, or perigree moon, occurs when a full moon is at its closest point to the earth, or its perigree, in its yearly elliptical orbit. It looks bigger than usual to all of us on earth gazing up because it’s only 221,765 miles (356,896 kilometers) away. So close!
Usually a supermoon happens every 13 months, but this year we are going to be treated to supermoon spectacles three times over the course of three months! A supermoon rose on July 12th and we’ll have a chance to marvel at yet another supermoon on September 9th. The one in August, however, is the closest. Astronomers warn that this trifecta of supermoons won’t happen again until 2034.
If you happen to miss the supermoon, fear not, there is more great stuff happening in the sky this week. The Perseid meteor shower is making its annual visit. Though actually, the Earth and the meteor shower are visiting each other.
Every year around this time in August, Earth crosses the orbital path of Comet Swift-Tuttle and encounters loads of comet debris. The dust and ice particles that make up this debris burn up as they zip through the earth’s atmosphere, letting us catch a glimpse of their paths across the sky. If a meteor is lucky enough to travel all the way to earth, it’s called a meteorite. Before the meteor hits the earth’s atmosphere, when it’s still just a rock minding its own business out in space, it’s called a meteoroid.
The best time for viewing the Perseid meteor shower is usually in the early morning. This year, however, the supermoon might get in the way with all its bright light. You can also spot meteors during early evening.
Choose a spot with little light pollution, such as an empty field or park. A few minutes after turning out all lights, your eyes will be adjusted to the dark and you’ll be able to see plenty of stuff in the sky.
These meteors are called the Perseid meteors because they look like they originate from the same area as the Perseus constellation, which can be found in the northeastern part of the sky, as you can see in the above illustration from NASA. Don’t worry too much about facing the right direction, though. Simply look up and a meteor will catch your eye.
Happy star gazing!