Don't look now, but the Perseid meteors are back.

The full contingent of meteors are still about a week out, and not expected to become meteorites — meteors that actually hit the Earth — so there's still time to get ready for the annual streaking light show.

City lights and cloudy weather could get in the way of what has become the most-watched meteor shower of the year, but solar conditions, according to NASA, should be perfect (moonless) throughout the night Monday and Tuesday, Aug. 11 and 12.

"Under moonless dark-sky conditions, observers away from city light pollution are usually able to see one and sometimes two Perseid meteors per minute," said Patrick Wiggins, NASA solar system ambassador to Utah. "This year's peak activity is set to occur during Tuesday's predawn hours when there will be no moon in the sky, making country skies even darker and meteors even more visible."

Some Perseid meteors may also be seen in the nights and mornings just before and after the 12th. The predawn hours on Aug. 12 will probably be the best time for Utahns to look, NASA astronomers advise, because that's when Earth will be nearly at the center and facing directly into the oncoming meteor swarm.

Perseids aren't back by popular demand but by galactic forces that set them adrift in the wake of fly-by comets, probably from their namesake constellation, Perseus, a northern constellation that at 28 degrees in length is one of the largest in our sky. For those who want to see where the particles likely originated, Perseus is easy to find because of what surrounds it — constellations such as the "W" of Cassiopeia, Auriga, Andromeda, Triangulum and Taurus. The Perseus Arm is one of four major spiral arms of our galaxy, the Milky Way. Earth is in the minor Orion Arm.

Perseus is a hero of Greek mythology most noted for killing the monster Medusa. If you look at Perseus under dark skies, you may be able to see three of the spiral arms that enfold the galaxy.

The meteor visit is more popular than other star shows because they aren't stars and aren't seemingly fixed in place. They're bits of rock burning up as they pass through Earth's atmosphere, leaving light tracers that are best viewed without telescopes or binoculars.

This is one astronomical event that is full sky and naked eye, Wiggins said, because the usual telescoping that provides a closer look at the stars actually limits the field of vision in a shower and would block out significant portions and size of it.

Technical aids needed for this encounter are a lawn chair, the naked eye and maybe a few snacks.

Often called shooting stars or falling stars, most meteors are actually tiny bits of rock, many no larger than a grain of sand, that burn up due to air friction when they strike Earth's extreme upper atmosphere. The resultant meteor ash then drifts harmlessly and invisibly to Earth.

Astronomers say Perseids could be the fastest meteors, traveling at about 60 kilometers per second when they hit Earth's atmosphere, or fast enough to go from Salt Lake to St. George in about 8 seconds.

Meteor particles are thought to be the dust trails left in the wake of comets. The comet that left the Perseid debris behind, Swift/Tuttle, is coming back, too, but not until 2126. It was last closest to Earth in the early 1990s.

For more information, visit utahastro.info.


E-mail: jthalman@desnews.com