Summer is a great time to be outdoors at night with clear skies and the prospect of seeing a shooting star. As you know, a shooting star is the common name for the bright streak of light given off by a meteor as it streaks into Earth’s atmosphere and burns up from the heat caused by friction with the air molecules.
Throughout the year there are brief periods when meteor activity peaks, we call these meteor showers. A meteor shower occurs as the Earth passes through a region of space that has a greater concentration of meteoroids, which are small rocky or metallic bodies too small to be classified as asteroids. These concentrations are typically the result of debris left behind by passing comets. For example a shower in May and one in October are chiefly caused by debris left behind by Halley’s comet.
During a meteor shower the Earth’s orbital path takes it into the path of a stream of debris. The meteoroids enter our atmosphere at high speeds on parallel trajectories, but from our perspective they appear to radiate from a central region. It is the constellation in this apparent central region that we use to name the shower. For example, the Geminids appear to radiate from the constellation Gemini and the Perseids appear to radiate from Perseus. Some showers are relatively tame with just 5-10 visible meteors per hour, but some such as the Leonids in November can produce several hundred visible meteors per hour.
Knowing when and where to look are the keys to seeing a great show. To find out what showers are coming up you can check various online resources (such as the International Meteor Organization at www.imo.net) for a schedule of upcoming showers. Meteor showers typically last several days to many weeks and these sites will also tell you when the peak activity period is expected to be and even approximately how many visible meteors, on average, are expected per hour.
Once you know the date and name of the shower you can use a planisphere (such as The Night Sky available here) to locate the radiant constellation and you will know exactly where to look.
The less light pollution you have to contend with the more meteors you will see, so get to a dark location and give your eyes 20-30 minutes to adapt to the dark. This is the perfect excuse to drive to a national park or favorite remote hiking trail. While you are out in the dark, use a red flashlight with wavelength of 620nm or more to find your way around without depleting your night vision.
Perseids – Peak August 12-13, 2015 – 50-75 meteors per hour.
August 12 will be just a few days past the new moon so viewing conditions should be good. With the large number of meteors per hour this is a good shower for the young ones because there should be quite a few to see as soon as it gets dark. The later you can stay out the more activity you should see.