The annual Perseid meteor shower occurs when debris from Comet Swift-Tuttle intercepts the Earth at a high velocity (59 km/s, 133,000 mph). This debris is somewhat diffuse, so we see activity for many days on either side of the peak. Like most meteor showers, this is named for the constellation its members appear to originate in: Perseus.

Shower Summary

This is a composite image of 361 meteors collected between sunset on August 4 through sunrise on August 13 (nine evenings). Mouse over the image to see just the 105 Perseids recorded on the peak night of August 12/13. Since the images were collected over many hours, the radiant of the shower is not in a fixed location. However, because most of the meteors occurred between 2am and dawn, and because the radiant's high declination means it doesn't move fast, most of the meteors appear to point back to the same general area of the sky - just above the left center of the image. Note also that meteors farther from the radiant tend to make longer trails, since they have a smaller component of their velocity towards the camera.

All 361 of the meteors in this composite are Perseids. Several showers are currently active (Alpha Capricornids, Southern Delta Aquarids, Kappa Cygnids), but meteors from those are not shown.

The southwest monsoon pattern generally affects weather in Colorado during August. Although we have had a number of storms, we are currently experiencing a bit of a dry spell, so conditions for capturing meteors have been good. The Moon interferes significantly with the Perseids this year, but during this early phase of the shower the skies are dark most of the night. The full Moon on the peak night of August 12/13 makes it less likely that dim meteors will be caught. In the composite, the Moon has been digitally removed.

Long string-like images are stars or planets captured as they traveled across the sky over many hours. Jupiter can be seen trailing across the sky in the lower left corner. Bright star trails are evident for Capella, Aldebaran, Deneb, Vega, and Altair.

Selected Fireball Videos

• 2011.08.05 03:54:18 MDT - bright terminal explosion
• 2011.08.08 03:36:57 MDT - bright terminal explosion, persistent train
• 2011.08.13 01:12:06 MDT
• 2011.08.13 04:41:57 MDT

Perseid Frequency

This graph plots the distribution of meteors during the peak and the surrounding days. The raw count is distributed in 4-hour bins. The peak for August 11 is probably not representative of the actual count, as there was some thin fog that morning, which combined with the bright moonlight resulted in some meteors being missed.