Alpha Centaurids Annually Shower Earth’s Skies Jan. 28 to Feb. 21

Summary: The Alpha Centaurids annually shower Earth’s skies Jan. 28 to Feb. 21, with visibility favoring the Southern Hemisphere and with peak activity Feb. 8.

February alpha Centaurid meteor shower appears to radiate from an area in southeastern Centaurus the Centaur constellation, near the southern constellation’s two brightest stars, Alpha Centauri (α Centauri; Alf Cen, α Cen) and Beta Centauri (β Centauri; Beta Cen, β Cen); Centaurus constellation map credit: IAU and Sky & Telescope (Roger Sinnott and Rick Fienberg; constellation patterns by Alan MacRoberts), CC BY 4.0 International, via IAU (International Astronomical Union)

The Alpha Centaurids annually shower Earth’s skies Jan. 28 to Feb. 21, primarily as a Southern Hemisphere-favoring meteor shower and with peak activity occurring Feb. 8.

The American Meteor Society’s Meteor Activity Outlook weekly columnist, Robert Lunsford, recommends pre-dawn viewing of the Alpha Centaurids. Best viewing in the Southern Hemisphere begins around 5 p.m. local standard time.

The Alpha Centaurid meteor shower disfavors the Northern Hemisphere. Dutch and American astronomer Peter Jenniskens, who is principal investigator at California’s SETI Institute, notes the shower’s lack of visibility in California. Recognized as a meteor expert, Jenniskens describes the shower as known for “annual activity and occasional meteor outbursts.”

Carl Hergenrother, staff scientist with University of Arizona’s Lunar and Planetary Laboratory and member of NASA’s OSIRIS-REX asteroid mission, viewed one Alpha Centaurid meteor on each of two consecutive days in February 2014 via his SALSA3 (Search for Alien Lights Over Southern Arizona) camera in Tucson. The Feb. 2 meteor’s visibility occurred at 7:04 a.m. The next day, Feb. 3, he detected an Alpha Centaurid meteor at 3:48 a.m. Hergenrother’s set up of three meteor surveillance cameras participated in the International Meteor Organization’s Video Meteor Network, run by Germany-based Sirko Molau.

Lunsford describes the Alpha Centaurid shower as producing “mostly swift meteors.” He places entry velocity at 56 kilometers per second (34.79 miles per second).

The shower’s name reflects the radiant (apparent point of origin) of its meteors near Alpha Centauri (α Centauri; Alf Cen, α Cen). The triple star system is located in the southeastern region of Centaurus the Centaur constellation. Alpha Centauri shines as the Centaur’s brightest star, as the night sky’s third brightest star and as the nearest star system outside the solar system.

Alpha Centauri has the traditional name of Rigil Kentaurus. The triple star’s traditional name derives from Arabic for “foot of the Centaur.” Greco-Roman astronomer Claudius Ptolemy (ca. 100-170 CE) describes Alpha Centauri as a first magnitude “star at the tip of the right forefoot” in his second-century, Greek-language, astronomical treatise, the Almagest (Ἡ Μεγάλη Σύνταξις, Hē Megalē Syntaxis, "The Great Treatise").

Centaurus the Centaur solely occupies the Southern Celestial Hemisphere, the southern half of the imaginary sphere projected by astronomy into space. Centaurus lies south of the celestial equator, an imaginary projection of Earth’s equator onto the celestial sphere.

In a July 1994 article in Astronomy and Astrophysics, Peter Jenniskens reported the results of a meteor counting study conducted over 11 years, between 1981 and 1991 by experienced amateur observers in the Netherlands and in Australia. Ten of the study’s 16 counters represented The Dutch Meteor Society (DMS). Six counters represented the North Australian Planetary Observers -- Meteor Section (NAPO-MS).

The study’s effective observing time totaled 4,482 hours. Southern Hemisphere counters accounted for 2,385 hours of observing time. Northern Hemisphere counters contributed 2,097 hours.

The study identified 110,538 meteors. The six observers in Australia enumerated 64,087 meteors. The study’s 10 Netherlands-based participants counted 46,451 meteors.

Over 199 hours of observing time, Australia’s six participants counted 297 Alpha Centaurid stream meteors. Counters placed the geocentric entry velocity of the Alpha Centaurid meteoroids into Earth’s atmosphere at 57 kilometers per second (35.41 miles per second).

The parent body of the Alpha Centaurids is unknown. Jenniskens finds that the shower’s peak times may be suggestive of a short-period Jupiter-type comet.

Carl Hergenrother notes that the unknown parent comet’s meteors display an orbit that is highly inclined to the ecliptic, the sun’s apparent annual path. He places orbital inclination at 107 degrees. The path followed by the shower’s meteors registers orbital perihelion inside Earth’s orbit, at 0.98 astronomical units.

Darkening lunar phases favor about half of the Alpha Centaurid meteor shower’s activity dates. The last quarter moon, offering 44 percent surface visibility Monday, Jan. 28, decreases to waning crescent visibility of 34 percent Tuesday, Jan. 29, slims to 11 percent visibility Friday, Feb. 1, and disappears with the new moon, Monday, Feb. 4. Peak activity coincides with the skimpy waxing crescent phase, with 7 percent visibility Thursday, Feb. 8, and 12 percent Friday, Feb. 8. Surface illumination increases with the first quarter phase Tuesday, Feb. 12, at 46 percent visibility and rises to 100 percent visibility with the full moon Tuesday, Feb. 19.

The International Astronomical Union (IAU), an international association of professional astronomers, is responsible for assigning designations and names to celestial bodies and objects. The IAU recognizes the Alpha Centaurid as 102 ACE.

The takeaways for the Alpha Centaurids, which shower Earth’s skies annually from Jan. 28 to Feb. 21, are that peak activity occurs Feb. 8 and that the shower’s parent body is unknown.

Triple star system Alpha Centauri’s binary star Alpha Centauri AB comprises Alpha Centauri A (left) and Alpha Centauri B (right): Hubble Telescope’s Wide-Field and Planetary Camera 2 (WFPC2); image credit ESA (European Space Agency)/NASA: NASA Hubble Mission Team Goddard Space Flight Center, "Hubble’s Best Image of Alpha Centauri A and B," NASA article Sep. 2, 2016, Generally not subject to copyright in the United States, via NASA

Acknowledgment

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

Image credits:

February alpha Centaurid meteor shower appears to radiate from an area in southeastern Centaurus the Centaur constellation, near the southern constellation’s two brightest stars, Alpha Centauri (α Centauri; Alf Cen, α Cen) and Beta Centauri (β Centauri; Beta Cen, β Cen); Centaurus constellation map credit: IAU and Sky & Telescope (Roger Sinnott and Rick Fienberg; constellation patterns by Alan MacRoberts), CC BY 4.0 International, via IAU (International Astronomical Union) @ https://www.iau.org/public/themes/constellations/#com

Triple star system Alpha Centauri’s binary star Alpha Centauri AB comprises Alpha Centauri A (left) and Alpha Centauri B (right): Hubble Telescope’s Wide-Field and Planetary Camera 2 (WFPC2); image credit ESA (European Space Agency)/NASA: NASA Hubble Mission Team Goddard Space Flight Center, "Hubble’s Best Image of Alpha Centauri A and B," NASA article Sep. 2, 2016, Generally not subject to copyright in the United States; may use this material for educational or informational purposes, including photo collections, textbooks, public exhibits, computer graphical simulations and Internet Web pages; general permission extends to personal Web pages, via NASA @ https://www.nasa.gov/image-feature/goddard/2016/hubbles-best-image-of-alpha-centauri-a-and-b

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