If you have been seeing some falling stars in the last few days it is probably because we are into perhaps the best meteor shower of the year. The earth is passing through the debris field of comet Swift-Tuttle from about July 17 to August 24.
Independently discovered by Lewis Swift and Horace Parnell Tuttle in 1862, comet Swift-Tuttle is one of the oldest known comets, with records dating back to China around 26 AD. It has an orbit that brought it near the earth in 1862 and then again in 1992 when it put on a rather unspectacular show. If you missed the 1992 show, you will have to wait until 2126 for the next pass through.
Comets are mixtures of ice, rock, and dust. Think of them as dirty snowballs a few miles in diameter. When comets pass near the sun, the heat causes the comet to shed ice and particles. These mostly sand-sized pieces of ice and rock create a “debris field” in outer space. When the earth passes through these debris fields, the pieces collide with the atmosphere and become glowing hot. Viewed from earth, they are “falling stars.” But of course we now know that they are meteors.
A lot of “falling stars” make a meteor shower. There are eight major meteor showers associated with comets each year. Even though the meteors in this shower originate from the comet Swift-Tuttle, the meteor shower is called the Perseids because the meteors are seen radiating out of the constellation Perseus. We will see the Orionids in October which appear to originate within the constellation Orion and are caused by debris from Halley’s Comet.
The meteor shower should increase in intensity until it peaks the night of August 11th and early morning of the 12th with upwards of 60 meteors per hour. Look to the northeast after midnight. A second quarter moon will detract from the viewing a bit. But even at that, the show could be well worth staying up for.
So make a point of getting out and observing the Perseids. If you are really lucky you may “catch a falling star.” If not, maybe you could pass the time singing that Perry Como hit from the '50s.