Perseid Meteor Shower Continues Through Late August

Summary: After peaking the night of Sunday, Aug. 12, to Monday, Aug. 13, the Perseid meteor shower continues through late August.

time-lapse image of Perseid meteor outburst, August 2009: NASA/JPL, via NASA Solar System and Beyond

The 2018 Perseid meteor shower, which peaked from Sunday night, Aug. 12, into the pre-dawn hours Monday, Aug. 13, continues through late August.

The Perseids’ shower run annually from about mid-July to late in August. The American Meteor Society places 2018 activity from July 13 to August 26.

The shower’s particles move swiftly across Earth’s skies. Particles assume a swift velocity of 37 miles per second (60 kilometers per second).

The American Meteor Society places particle zenithal hourly rate (ZHR) at 100. The zenithal hourly rate references the rate produced by a meteor shower in a clear, dark sky, with the radiant at its zenith, or highest point. Peak night may generally yield upward from 50 to 80 shower members per hour.

August’s great meteor shower derives its name from its radiant, or apparent point of origin, in Perseus the Hero constellation. The Perseid radiant is located near Eta Persei (η Persei; η Per, Eta Per). The binary star lies between the Greek mythological hero’s invisibility helmet and his sword-wielding, upraised arm.

The Perseid meteor shower primarily favors the Northern Hemisphere. Amateur astronomer and writer Gary W. Kronk directs mid-northern latitude observers to look for the radiant in the northeast.

Perseus the Hero appears in the Northern Celestial Hemisphere, the northern half of the imaginary sphere projected outward from Earth’s surface. The Hero claims Cassipoeia the Queen and Camelopardalis the Giraffe (Ancient Greek: κάμηλος, kámēlos, “camel” + πάρδαλις, párdalis, “leopard”) as northern neighbors in the starry skies. Aries the Ram and Taurus the Bull lie to the Hero’s south.

The Perseids disfavor the Southern Hemisphere, where the radiant stays below the horizon. Kronk suggests that mid-southern latitude viewers track the northern horizon for shooting stars. Although the radiant remains below the horizon, part of Perseus climbs above the horizon at this time. Kronke notes that mid-southern latitude observers may be rewarded with 10 to 15 meteors shooting up from the northern horizon on peak night.

The Perseids visually testify to Earth’s intersection with comet 109P/Swift-Tuttle’s orbital debris trails around the sun. Robert Lunsford, the American Meteor Society’s weekly Meteor Activity Outlook columnist, explains that variability in Swift-Tuttle’s paths through the inner solar system account for yearly variations in the prolific shower’s visibility. Earth’s passage through Swift-Tuttle’s debris trails usually occurs between the comet’s paths. Enhanced activity, known as an outburst, ensues from Earth’s encounter with the center of one of Swift-Tuttle’s paths.

The Perseid meteor shower’s parent body is comet 109P/Swift-Tuttle. American astronomers Lewis A. Swift (Feb. 29, 1820-Jan. 5, 1913) and Horace Parnell Tuttle (March 17, 1837-Aug. 16, 1923) share independent discovery of the Perseids' parent comet. Swift's discovery was July 16, 1862. Tuttle's discovery happened July 19, 1862. 

Swift-Tuttle is a periodic comet, with an orbital period of approximately 133 years.  Carnegie Institution staff scientist John E. Chambers describes comet 109P/Swift-Tuttle as “the largest known object in the Solar System whose current orbit allows it to make repeated close approaches to the Earth” (1995). Currently in a 1:11 orbital resonance with Jupiter, Swift-Tuttle completes one orbit for every 11 orbits logged by Jupiter. Chambers predicts capture within the resonance until at least 7000 C.E.

The Perseids’ shooting stars comprise variously sized particles of cometary dust and ice. Bill Cooke, lead of NASA’s Meteoroid Environments Office in Huntsville, north central Alabama, muses: “Here’s something to think about. The meteors you’ll see this year are from comet flybys that occurred hundreds if not thousands of years ago. And they’ve traveled billions of miles before their kamikaze run into Earth’s atmosphere” (2016).

The Perseid peak night, Sunday, Aug. 12, experienced ideal lunar conditions. The moon’s new phase, with onset Friday, Aug. 10, at 09:58 Universal Time (5:58 a.m. Eastern Daylight Time), was transitioning to a waxing crescent. The lunar sliver offered only around 2 percent visibility.

The Perseid peak night closed the August weekend that opened with 2018’s third of three partial solar eclipses. The partial solar eclipse Saturday, Aug. 11, was 2018’s only Northern Hemisphere solar eclipse. August’s partial solar eclipse also closed the year’s quintet of two lunar and three solar eclipses.

The takeaway for the Perseid meteor shower continuing through late August is that the prolific shower dominates the Northern Hemisphere’s last summery month, offering peak night mid-month and putting on nightly shows for most of the month.

near-Earth perspective of Perseid meteor shower radiant and of intersection of Earth's orbit (red) with comet 109P/Swift-Tuttle's orbital debris trail: Aanderson @amherst.edu, CC BY SA 4.0 International, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

time-lapse image of Perseid meteor outburst, August 2009: NASA/JPL, via NASA Solar System and Beyond @ https://www.nasa.gov/topics/solarsystem/features/watchtheskies/perseid-meteor-shower-aug11-12.html

near-Earth perspective of Perseid meteor shower radiant and of intersection of Earth’s orbit (red) with comet 109P/Swift-Tuttle’s orbital debris trail: Aanderson @amherst.edu, CC BY SA 4.0 International, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Perseid_Meteors_and_Comet_Swift-Tuttle.png

For further information:

“2018 Perseid Meteor Shower.” Time And Date > Sun & Moon > Meteor Showers.
Available @ https://www.timeanddate.com/astronomy/meteor-shower/perseid.html

Chambers, J. (John) E. “The Long-Term Dynamical Evolution of Comet Swift-Tuttle.” Icarus, vol. 114, issue 2 (April 1995): 372-386.
Available via ScienceDirect @ https://www.sciencedirect.com/science/article/pii/S001910358571069X?via%3Dihub#!

Espenak, Fred. "Phases of the Moon: 2001 to 2100." Astro Pixels > Ephemeris > Moon > Six Millennium Catalog of Phases of the Moon > Moon Phases in Common Era (CE).
Available @ http://astropixels.com/ephemeris/phasescat/phases2001.html

Harbaugh, Jennifer. “Look Up! Perseid Meteor Shower Peaks Aug. 11-12.” NASA > Solar System and Beyond > All Topics A-Z > Meteors & Meteorites > Watch the Skies. Aug. 2, 2016.
Available @ https://www.nasa.gov/topics/solarsystem/features/watchtheskies/perseid-meteor-shower-aug11-12.html

Jenniskens, Peter. Meteor Showers and Their Parent Comets. Cambridge, England: Cambridge University Press, 2006.

Kippax, John R. The Call of the Stars: A Popular Introduction to a Knowledge of the Starry Skies. New York NY; London, England: The Knickerbocker Press, 1914.
Available via Internet Archive @ https://archive.org/details/callofstarspopul00kipprich

Kronk, Gary W.. “Perseids.” Meteor Showers Online > Meteor Shower Calendar > August.
Available @ http://www.meteorshowersonline.com/perseids.html

Lunsford, Robert. Meteors and How to Observe Them. Astronomers’ Observing Guides. New York NY: Springer Science+Business Media, 2009.

Lunsford, Robert. “Viewing the Perseids in 2017.” Aug. 7, 2017.
Available @ https://www.amsmeteors.org/2017/08/viewing-the-perseids-in-2017/

Marriner, Derdriu. “Partial Solar Eclipse Aug. 11 Is Third of Three 2018 Solar Eclipses.” Earth and Space News. Wednesday, Aug. 8, 2018.
Available @ https://earth-and-space-news.blogspot.com/2018/08/partial-solar-eclipse-aug-11-is-third.html

“Meteor Shower Calendar.” American Meteor Society > Meteors.
Available @ https://www.amsmeteors.org/meteor-showers/meteor-shower-calendar/