Driftless Dark Skies: Reliable Perseids

Every year in August, our planet passes through the debris stream left behind by Comet Swift-Tuttle and our starry skies are streaked by Perseid meteors. Meteors from this and other showers will be visible all month, but the peak is predicted for the night of August 11/12 when we might see dozens every hour. 2020 is an especially good year since moonlight will not interfere for much of the night.

You can see more meteors after midnight when our part of the planet is plowing directly into the swarm. But the meteors before midnight have their charms. There are fewer of these “earthgrazers”, but they move more slowly and leave longer trails. Sunset in the Driftless is around 8:10, and the sky will be fully dark by 10:00. You will see meteors in any part of the sky, but I like to face north or east to keep an eye on the constellation Perseus from where the meteors appear to originate. It’s right below the big “W” of Cassiopeia. Find a safe spot away from town lights, turn off phones and flash lights so your eyes can adapt to the dark, bring a blanket or air mattress or reclining chair to be comfortable, and don’t forget your snacks. Include the kiddos and make it a fun teachable moment and special memory.

If the skies are clear, we should have a great show until just after midnight when the Last Quarter Moon rises in the ENE. That’s a great opportunity to ponder our place in the solar system and our galaxy. The lit half of the Moon is pointed toward the Sun. When you face the Last Quarter Moon, you are looking in the direction that Earth is traveling as we orbit the Sun at 65,000 mph. Also notice our fellow planets. Jupiter and Saturn will be bright low in the southern sky. Mars rises in the east around 10:45. As your eyes dark adapt, you will be awed by the sight of our galaxy, The Milky Way, streaming from Sagittarius the Archer in the south to Cassiopeia in the northeast.

The meteors we see are only the size of seeds, but they are so bright because they are coming in at over 100,000 mph. And “seed” is a good reminder that early in Earth’s history, it was comets such as Swift-Tuttle that brought the water and organics that made life possible. Comet Swift-Tuttle last flew by the Sun in 1992 and is due back in 2125. With each encounter, it loses about 1/1000 of its ice and dust to create the Perseid meteors that so reliably light up our August evenings. Meanwhile Earth and our sibling planets continue to orbit our star as it makes its way around the galaxy. We abide.

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador and the International Astronomical Union as a Dark Sky Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies. Driftless Dark Skies appears monthly in the Voice of the River Valley.