The Perseid Meteor Shower
The Perseid meteor shower will peak on the nights of August 11, 12, 13 during 2020.
A Perseid meteor over Washington, DC. Image Credit: NASA/Joel Kowsky
The Perseid meteor shower peaks every during mid-August, with the best nights for observing meteors in 2020 occurring from the 11th to the 13th. The Perseid meteor shower comes from pieces of comet debris left in the wake of comet 109P/Swift-Tuttle. That comet loops through the solar system once every 133 years with an orbit that happens to intersect with Earth's orbit. Swift-Tuttle last passed through the solar system in 1992, but there is a continuous debris train left in the wake of the comet. So, every time we cross through the orbit of Swift-Tuttle during August, that train of debris hits the Earth's atmosphere.
Since Swift Tuttle is a large comet, about 16 miles or 26 kilometers across, it is able to shed a large quantity of debris. As some of the ice that makes up a portion of the comet vaporizes when it passes through the inner solar system, all the small bits of rock that are mixed are blown off into space, left to orbit the sun on their own. Since most of those bits of rock are the size of tiny sand grains, it is rare for a Perseid meteor to reach the surface of the Earth. However, there are a lot of debris particles, and they are all moving extremely fast, about 59 km/s or about 125,000 mph. So, even though they are small, because of their great speed they still hit the atmosphere with a great deal of force and glow brightly as they rapidly burn up in the atmosphere.
Most Perseid meteors start burning up between 105-110 km above the surface and completely burn up between 75 and 95 km above the ground, with the larger meteors making it down to about 75 km.
Even though the meteor shower originates from comet Swift-Tuttle, it is called the Perseid meteor shower because the meteors appear to come from the constellation Perseus. The meteors can be seen all over the night sky, but if you draw a line parallel to the streak of light each meteor makes, all of them will intersect in the constellation Perseus.
The Perseid meteor shower is famous because it often produces 50-75 meteors per hour when observed from a dark site, with peak intensity often over 100, and it occurs during the middle of August when warm nights make for pleasant observing. The Geminid meteor shower in mid-December (peaks on the 13th-14th in 2020) usually produces more meteors, and brightly colored ones as well. However, because of poor weather conditions at that time of year, having both a clear night when the shower peaks and moderate temperatures are less common for many locations.
You can play with the interactive Perseid meteor shower simulation below. The white dots represent individual meteors. The third circle from the sun of course represents the Earth's orbit.