Sideways Orion

August meteor showers  August 4, 2015

Although there are months with more meteor showers, and more productive meteor showers, August is known as the meteor shower month. That’s probably because being outside at 2 or 3 am in August depends mostly on whether or not you’re the kind of person who’s up at 2 or 3 AM, whereas being outside at 2 or 3 AM in November depends more on whether or not you have insomnia or have lost touch with reality. Even if you are the sort of person who is normally up at 2 or 3 AM, it’s a lot easier to convince yourself to go outside when it’s 60° than when it’s 6°. So let’s take a look at the August meteor showers.

First things first: what makes it a meteor shower? On a typical, average, non-meteor shower night, under dark skies you should expect to see six or seven meteors per hour. They’ll be spread randomly around the sky though, so it’s unusual for a single observer to see them all. Meteor showers occur when the meteors seem to come from a particular area of the sky, called the radiant. It usually also means more meteors, but the radiant is the important part. You’ll  generally see more meteors in the predawn sky since that’s when the sky overhead is facing the direction or his traveling. Think of it like when you’re driving in the car: more bugs hit the windshield then the side or back of the car.

The top diagram shows the time of day on Earth. The second diagram shows the direction Earth is traveling in its orbit. If you put those two together, you get the bottom diagram, showing that the part of Earth where it is both dark AND running into the meteors.

The Perseids are of course the best-known meteor shower, and with good reason. With maximum rates reaching close to 100 in good years, it’s a reasonably active shower. Many of the meteors are also bright, so you can expect to see 10 or so even under moderately light polluted skies. They tend to be quick though, and don’t have persistent trains (they won’t leave a streak on the sky for a long time.) The number of meteors gradually builds from about mid July until the peak around the 12th or 13th, then drops dramatically right after the peak.  The show runs about two more weeks, gradually tapering off by about the 26th or 27th.

The 2015 peak should occur on August 13. The American meteor society (AMS) predicts a rate of about 50 to 75 meteors per hour. The radiant is actually circumpolar for most of the US & Canada, so anytime after midnight is worth going out, but it’ll be best around 3 – 5 AM, when the radiant is high in the northeast, and twilight hasn’t begun. Check the chart at the end for it’s location at 4 AM.

The Perseids aren’t the only show this month.

The Alpha Capricornids are a low rate shower, just around 5 an hour. However, it’s tendency to produce fireballs makes it worth watching for patient people. It peaked around July 29, but the difference between the peak and not peak is nearly insignificant. If you’re already out hunting early Perseids, you might as well find a spot where you can also see the southwest!

The Delta Aquariids  also peaked around July 29, but you’ll continue to see several of these every night until late August. These are faint, though, so avoid the waning moon nights, and find someplace dark. The radiant is pretty far south too, so the farther south you are, the better.

There are also a few other recognized meteor showers, but they have very low numbers. If you happen to have a clear night when you’ll be at a dark site, you should check out the weekly meteor outlook at the AMS. Also, if you happen to spot a fireball, you can help identify and track it by reporting it!

meteorShower (pdf)