A sure-fire summer shower, the Perseid meteors are set to put on a spectacular show this year.
It’s one of my fondest astronomical observing memories of childhood. Growing up in Northern Maine, it was a family tradition to set the lawn chairs out on warm mid-August nights, and watch with my mom and brother as the Perseid meteors slid silently through the inky black sky.
Though I now reside in light-polluted Norfolk Virginia, the family tradition continues… and you couldn’t ask for a better year than 2021 for the Perseid meteors.
The position of the radiant in Perseus. Credit: the American Meteor Society.
Circumstances for the Perseid meteors in 2021: This year, peak is set for Thursday, August 12th at around 12:00 Universal Time (UT)/8:00 AM Eastern Time (EDT), favoring the Pacific Rim region. With an expected maximum Zenithal Hourly Rate (ZHR) = 110 meteors per hour, the 2021 Perseids occur just three days prior to the Moon reaching 1st Quarter, setting well before local midnight. Live elsewhere? Do not despair: meteor showers often fail to heed predictions, and instead may ramp up hours before or after the expected maximum; the Perseids in particular are notorious for a double, ‘twin’ peak’ spanning several hours. For Europe and eastern North America, the key time to watch is in the early dawn hours of August 12th. Clouded out? If skies are clear, I’d start watching for Perseids from the morning of August 10th onwards or even starting this coming weekend, as there are always early stragglers.
Looking eastward at midnight from latitude 30 degrees north. Credit: Stellarium
Radiating from the constellation of Perseus the Hero of Greek mythos, the Perseids are also sometimes known as the ‘Tears of Saint Lawrence’ referring to the saint who was martyred on a hot grid iron on August 10th, 258 AD. The Perseids are one of the longest running and most dependable of the annual major meteor showers, vying only with the December Geminids in recent years.
An early 2021 Perseid pierces the plane of the Milky Way Galaxy. Image credit and copyright: Peter Forister (@forecaster25)
The source of the Perseids is periodic comet 109/P Swift-Tuttle. This comet was discovered in 1862, and made its next perihelion post-discovery in 1992. On a 133 year orbit, The Perseids have been a known shower since the mid-19th century, and the passage on Swift-Tuttle through the inner solar system three decades ago has assured strong annual returns for the shower through the early 21st century.
In recent years, the Perseids have topped out at a maximum ZHR of 100 in 2020 and 80 in 2019, with the peak arriving very near a Full Moon. That’s a testament to the high ratio of fireballs that the Perseids tend to produce. The last year where the peak hit near New Moon was 2015, with a resulting ZHR of ~95.
The zenithal points for the Perseids at their peak on August 12th, versus the Sun-Moon angle. Credit: Orbitron.
Observing Perseids is as simple as scanning the sky and waiting for one to slide past. The only tools you need are a working pair of ‘Mk-1 eyeballs,’ bug spray (mosquitoes can be fierce in August), and patience. I like to keep a pair of binoculars handy to examine any lingering bolide trails, and I run a voice recorder (or these days, a voice recorder App on my phone) to keep track of meteor counts. Also, you can ‘hear’ pings from meteors on the AM radio band, when tuned to an unoccupied spot on the dial.
When it comes to watching for meteors, darkness is your friend. Be sure to scout out as dark a site as you can possibly find; light pollution can cut your observed count down considerably. In 2021, the Moon is out of the scene (a plus)… but when we say ‘Zenithal Hourly Rate,’ we’re talking about an extrapolated, ideal number you’d expect to see under pristine skies, with the radiant directly overhead at the zenith. Unfortunately, none of us have this sort of situation, but you can optimize your chances by searching out as dark a site as you can possibly find.
Be sure to report those meteor counts to the International Meteor Organization. It’s a great way to contribute to real science and the understanding of how meteor streams evolve.
If skies are clear, be sure to check out the Perseid meteors in the coming week… we won’t get another ‘near perfect’ season for them for years to come.
Lead image credit: A 2019 Perseid slices through the night sky. Credit: Mary McIntyre.