2018 Leonids Peak Saturday Night, Nov. 17, to Pre-Dawn Sunday, Nov. 18

Summary: The 2018 Leonids peak Saturday night, Nov. 17, to pre-dawn Sunday, Nov. 18, as a major meteor display showering most of November annually.

Leonid shooting stars have an apparent point of origin, known as radiant, in Leo the Lion constellation’s Sickle asterism, or pattern of stars: Popular Science @PopSci, via Twitter Nov. 16, 2015

The American Meteor Society (AMS) notes that the 2018 Leonids peak Saturday night, Nov. 17, to pre-dawn Sunday, Nov. 18, as a major meteor shower that occurs annually in November.

The International Meteor Organization (IMO) gives an earlier date for 2018’s peak. The IMS dates 2018’s peak night to Friday night, Nov. 16, to pre-dawn Sunday, Nov. 17.

The moon interferes somewhat with visibility of the Leonid meteor shower’s peak. The moon’s first quarter phase begins Thursday, Nov. 15, with 49 percent surface visibility of the lunar disk. The waxing gibbous phase takes over Saturday, Nov. 17, claiming 68 percent surface visibility. Surface visibility bounds to 77 percent for Sunday, Nov. 18.

The Leonid meteor shower’s November activity occurs as an autumn display in the Northern Hemisphere and, oppositely, as a spring display in the Southern Hemisphere. American amateur astronomer Gary W. Kronk suggests that mid-northern latitude observers face Leo the Lion’s easterly placement above the horizon at around 2 a.m. local time. Mid-southern latitude observers find the Leonid radiant above the horizon in the northeast at around 3 a.m. local time.

The AMS predicts 2018 activity dates of Monday, Nov. 5, through Friday, Nov. 30. The IMS slightly delays the 2018 opening date. The IMO considers Tuesday, Nov. 6, as opening the year’s Leonid meteor showers but agrees on Friday, Nov. 30, as closing date.

Moonlight does not intrude upon the Leonid meteor shower’s opening dates. A waning crescent has been steadily decreasing in size since its appearance Friday, Nov. 2, with 30 percent surface visibility. Monday, Nov. 5, yields a waning crescent downsized to a skimpy 6 percent. The waning crescent Tuesday, Nov. 6, shrinks to 2 percent surface visibility.

The 2018 shower’s final days contend with the moon’s waning gibbous and last quarter phases. Sunday, Nov. 25, opens November 2018’s last week with a waning gibbous moon at 94 percent surface visibility. By Wednesday, Nov. 28, the waning gibbous moon shines at 68 percent visibility. The Friday, Nov. 30, last quarter phase offers 45 percent surface visibility.

The Leonid meteor shower’s name announces an apparent point of origin, known as the radiant, in Leo the Lion constellation. EarthSky website’s editor-in-chief, Deborah Byrd, explains that an Earthbound observer who traces Leonid activity backward in the sky arrives at an apparent starting point near Leo’s Gamma Leonis (γ Leonis; Gamma Leo, γ Leo).

Gamma Leonis comprises two gravitationally-bound stars, known as a binary star system. The orange-red, greenish-yellow system bears the traditional name of Algieba (Arabic: al-Jabhah, “the forehead”). Algieba numbers among six stars shaping Leo’s distinctive Sickle asterism, or pattern of stars. Appearing as a backward question mark, the Sickle seems to shoot Leonid meteors like fireworks far beyond the Lion’s celestial territory.

The American Meteor Society and the International Meteor Organization recognize the swift velocity of the Leonid meteor shower’s particles. Both organizations time Leonid velocity at 44 miles per second (71 kilometers per second).

The zenithal hourly rate (ZHR) idealizes a shower’s observable rates by considering optimal radiant and sky conditions. The Leonids claim a zenithal hourly rate of 15 shower members per hour.

The Leonids consist of debris shed by comet 55P/Tempel-Tuttle. NASA Jet Propulsion Laboratory’s Solar System Dynamics website calculates Tempel-Tuttle’s orbital period at 33.24 years, or 12,141.56115249823 days. With an orbital period under 200 years, Tempel-Tuttle qualifies as a short-period comet.

Solar System Dynamics website’s JPL Small-Body Database Browser places the Leonid meteor shower’s parent body between Uranus and Neptune during the November 2018 peak. At 00:00 (midnight) Coordinated Universal Time, Sunday, Nov. 18 (7 p.m. Eastern Standard Time, Saturday, Nov. 17), comet 55P/Tempel-Tuttle is traveling beyond Uranus the sideways planet’s orbit. Earth distance is 19.905 astronomical units (au). Sun distance measures 18.923 au.

One astronomical unit roughly equals the distance between Earth and the sun. The unit’s exact measurement is 149,597,870,700 meters (about 150 million kilometers; 93 million miles).

The takeaway for the 2018 Leonid peak Saturday night, Nov. 17, to pre-dawn Sunday, Nov. 18, is that the major meteor shower occurs in November as a spring display in the Southern Hemisphere and as an autumn meteoric event in the Northern Hemisphere.

orbital position of Leonid parent body, Comet 55P/Tempel-Tuttle, at 00:00 (midnight) Coordinated Universal Time, Sunday, Nov. 18 (7 p.m. Eastern Standard Time, Saturday, Nov. 17), during 2018 peak, Saturday night, Nov. 17, to pre-dawn Sunday, Nov. 18, 2018: JPL’s Solar System Dynamics, May be used for any purpose without prior permission, via NASA Jet Propulsion Laboratory

Acknowledgment

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

Image credits:

Leonid shooting stars have an apparent point of origin, known as radiant, in Leo the Lion constellation’s Sickle asterism, or pattern of stars: Popular Science @PopSci, via Twitter Nov. 16, 2015, @ https://twitter.com/PopSci/status/666465838812151810

orbital position of Leonid parent body, Comet 55P/Tempel-Tuttle, at 00:00 (midnight) Coordinated Universal Time, Sunday, Nov. 18 (7 p.m. Eastern Standard Time, Saturday, Nov. 17), during 2018 peak, Saturday night, Nov. 17, to pre-dawn Sunday, Nov. 18, 2018: JPL’s Solar System Dynamics, May be used for any purpose without prior permission, via NASA Jet Propulsion Laboratory @ https://ssd.jpl.nasa.gov/sbdb.cgi?ID=c00002_0;old=0;orb=1;cov=0;log=0;cad=0#orb

For further information:

“55P/Tempel-Tuttle.” NASA Jet Propulsion Laboratory Solar System Dynamics > JPL Small-Body Database Browser.
Available @ https://ssd.jpl.nasa.gov/sbdb.cgi?ID=c00055_0

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

Astronomy Now ‏@AstronomyNow. “Clear skies? Don't miss the Northern #Taurid meteor shower's peak today.” Twitter. Nov. 12, 2015.
Available @ https://twitter.com/AstronomyNow/status/664743001235804160

Byrd, Deborah. “November’s Leonid Meteor Shower.” EarthSky > Astronomy Essentials. Nov. 15, 2018.
Available @ http://earthsky.org/?p=29831

International Meteor Organization. “Leonids.” International Meteor Organization > Resources > Meteor Shower Calendar.
Available @ https://www.imo.net/resources/calendar/2018/

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

Kronk, Gary W. “Observing the Leonids.” Meteor Showers Online > Meteor Shower Calendar > November Radiants.
Available @ http://meteorshowersonline.com/showers/leonids.html

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

Marriner, Derdriu. “2015 Leonid Meteor Shower Peaks Before Dawn Between Nov. 17 and 18.” Earth and Space News. Tuesday, Nov. 17, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/11/2015-leonid-meteor-shower-peaks-before.html

Marriner, Derdriu. “November Nights: Orion Dodges Taurid Fireballs, Leonids Shower Jupiter.” Earth and Space News. Thursday, Nov. 5, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/11/november-nights-orion-dodges-taurid.html

McClure, Bruce; and Deborah Byrd. “EarthSky’s 2018 Meteor Shower Guide.” EarthSky > Astronomy Essentials. July 6, 2018.
Available @ http://earthsky.org/astronomy-essentials/earthskys-meteor-shower-guide

“Moon Phases November 2018.” Calendar-12.com > Moon Calendar > 2018.
Available @ https://www.calendar-12.com/moon_calendar/2018/november

Popular Science @PopSci. “Look to the skies at midnight (your local time) to see tonight’s Leonid meteor shower.” Twitter. Nov. 16, 2015.
Available @ https://twitter.com/PopSci/status/666465838812151810

Shekhtman, Lonnie; Elizabeth Landau; and Celeste Hoang. “55P/Tempel-Tuttle.” NASA Science Solar System Exploration > Small Bodies > Comets. Updated Dec. 5, 2017.
Available via NASA Science Solar System Exploration @ https://solarsystem.nasa.gov/small-bodies/comets/55p-tempel-tuttle/in-depth/