100 Shooting Stars Per Hour To Light Up San Diego Sky

By Susan Murphy, KPBS

More than 100 shooting stars per hour, formally called meteors, will streak across the San Diego sky Sunday and Monday nights during the peak of the annual Perseid meteor shower.

The event occurs every August when the earth passes through a trail of dust from the comet Swift-Tuttle, which has a nucleus of approximately 16 miles.

“When the earth passes through this cloud of material, these dust particles enter the earth’s atmosphere at very high velocity and that causes meteors of streaks of light across the sky,” explained Allen Shafter, chair of the department of astronomy at San Diego State University.

This dusty debris falls into Earth's atmosphere at speeds of more than 100,000 miles per hour, or 37 miles per second, and burns up, creating the fiery light show.

Most of the dust particles are the size of a grain of sand or smaller, said Shafter.

“But some of the particles can get bigger," he said. "And if they get big enough, they can actually survive their passage through the earth’s atmosphere. When that happens, it hits the surface of the earth and we have a meteorite,” Shafter added.

Fast facts:

The dust particles that create Perseid meteors were born in the comet known as 109P/Swift-Tuttle. This object orbits the sun once every 130 years.

Although 37 miles per second may seem fast, Perseid meteors are not the quickest among annual showers. The Leonids of November top the charts, hitting our atmosphere at 44 miles per second.

Although most meteors meet their demise high in Earth’s atmosphere at altitudes between 50 and 70 miles, a few bigger particles survive within 12 miles of the surface. These typically produce “fireballs” that glow as bright as or brighter than Venus.

Shafter said the bigger the particle, the brighter the meteor.

“When we get a really big particle colliding with the earth’s atmosphere, we get what’s called afireball. A fireball is nothing more than a really bright meteor.”

Shafter said this year’s show should be particularly vibrant because the moon will be in crescent form and will set early.

"So from 10 p.m. until dawn the next day, the sky will be very dark and that will allow people to see the maximum number of meteors,” said Shafter.

Shafter said the show will gain momentum after midnight.

“Because as the earth goes around the sun, it’s also rotating," said Shafter, "and between midnight and dawn, you get the maximum impact velocity with the earth’s orbit and the dust particles.”

Shafter said the best place for viewing is away from bright city lights, such as Pine Valley, Mt. Laguna and the Anza Borrego Desert.

"The best thing to do is sit there and stare at the sky," he said. "You don't need any special equipment, not even binoculars. Just the naked eye."

Stargazers can gear up for the big celestial show Saturday night in Julian at the Julian StarFest. The free public event will allow attendees to look through telescopes and ask questions to experts.