This month, the Perseid meteor shower is lighting up the night sky. The meteor shower is visible every year from around July 17th to August 24th and peaks around August 13th. The Perseids are produced by debris from the Swift-Tuttle comet, which is the largest solar system object to pass close to Earth repeatedly. Swift-Tuttle is a 16-mile-wide ball of dust, ice, and rock. It was discovered in 1862 independently by both Lewis Swift and Horace Parnell Tuttle, hence the name. Its debris stream contains particles that are a bit larger than those in an average comet or asteroid debris stream so they tend to produce brighter meteors.
According to NASA, approximately 30 meteor showers occur each year that are visible to observers on Earth. The Perseid meteor shower was first observed in China about 2,000 years ago. When viewing conditions are good, sky watchers can expect to see as many as 30 to 100 meteors blazing overhead each hour during the Perseids. Ideal viewing conditions are clear, dark skies, and specifically International Dark Sky Parks, which we wrote about here
, but you should be able to view the Perseids in an area away from light pollution. Viewers don’t need any special equipment: the naked eye is fine. Another component to ideal viewing is the phase of the moon. Too much moonlight can obscure a meteor shower. This year, the moon will be in a waxing crescent phase and will set several hours before the celestial fireworks really begin so conditions are ideal for the 2021 Perseids.
Meteor showers occur when the Earth crosses through fields of cosmic debris shed by passing comets and asteroids. Particles from asteroids or comets collide with the Earth’s atmosphere at speeds up to 133,000 mph and burns up in a brilliant flare of light — a Perseid meteor. Meteor showers are named after the constellation from where the shower appears to be coming from, known as the radiant. The Perseids is named after the constellation Perseus the Hero. In ancient Greek star lore, Perseus is the son of the god Zeus and the mortal Danaë. It is said that the Perseid shower commemorates the time when Zeus visited Danaë in a shower of gold.
When watching meteor showers, viewers are seeing meteors ejected from the parent comet from earlier orbits – not the comet’s most recent orbit. This is because it takes time for debris from a comet’s orbit to drift into a position where it intersects with the Earth’s atmosphere.
The Perseids is one of three ideal meteor showers that can be seen in 2021. The good news is that it is also the first, so there are two more chances to catch a celestial show, including the Draconid meteor shower that will peak around October 8-9th, and the South Taurid meteor shower on November 4-5th.