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

For further information:

“00102 ACE alpha Centaurids.” IAU (International Astronomical Union) Meteor Data Center > List of All Meteor Showers.
Available @ https://www.ta3.sk/IAUC22DB/MDC2007/Roje/pojedynczy_obiekt.php?kodstrumienia=00102&colecimy=&kodmin=00001&kodmax=01032&sortowanie=

Espenak, Fred. “Phases of the Moon: 2001-2010 Universal Time.” AstroPixels > Ephemeris > Moon > Six Millennium Catalog of Phases of the Moon: Moon Phases From -1999 to +4000 (2000 BCE to 4000 CE).
Available @ http://astropixels.com/ephemeris/phasescat/phases2001.html

Espenak, Fred. “Rigil Kentaurus -- Alpha Centauri.” AstroPixels > Observing Resources Page > Astronomy Information > Additional Links > Star Catalogs > 152 Brightest Stars Through Magnitude 3.00.
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Garfinkle, Robert. Star-Hopping: Your Visa to Viewing the Universe. Cambridge, England: Cambridge; New York NY; Melbourne, Australia: University Press, 1994.

Hergenrother, Carl. “Beginning of February Meteors.” The Transient Sky -- Comets, Asteroids, Meteors > Archives > February 2014. Feb. 10, 2014.
Available @ https://transientsky.com/2014/02/10/beginning-of-february-meteors/

Hergenrother, Carl. “The Tucson-Based SALSA Meteor Camera.” The Transient Sky -- Comets, Asteroids, Meteors > Archives > August 2009. Aug. 15, 2009.
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Jacchia, Luigi G.; Fred L. Whipple. “Precision Orbits of 413 Photographic Meteors.” Smithsonian Contributions to Astrophysics, vol. 4 (September 1961): 97-129.
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Jenniskens, P. (Peter). “Meteor Stream Activity. I. The Annual Streams.” Astronomy and Astrophysics, vol. 287 (1994): 990-1013.
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://articles.adsabs.harvard.edu/full/1994A%26A...287..990J

Jenniskens, P. (Peter). “Meteor Stream Activity. II. Meteor Outbursts.” Astronomy and Astrophysics, vol. 295 (1995): 206-235.
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Jenniskens, Peter. Meteor Showers and Their Parent Comets. Cambridge, England: Cambridge University Press, 2006.

Jenniskens, Peter; Peter S. Gural; David Holman. “The Established Meteor Showers as Seen in Video Meteoroid Orbit Surveys.” Marc Gyssens and Paul Roggemans, eds., Proceedings of the International Meteor Conference, La Palma, Canary Islands, Spain, 20-23 September 2012. Hove, Belgium: The International Meteor Organization, January 2013.
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Kronk, Gary W. “Alpha & Beta Centaurids.” Meteor Showers Online > Meteor Shower Calendar.
Available via Internet Archive Wayback Machine @ https://web.archive.org/web/20071130152917/http://meteorshowersonline.com/showers/alpha-beta_centaurids.html

Lunsford, Robert. “Meteor Activity Outlook for Feb. 10-16, 2018.” American Meteor Society. Feb. 9, 2018.
Available @ https://www.amsmeteors.org/2018/02/meteor-activity-outlook-for-february-10-16-2018/

Lunsford, Robert. “Meteor Activity Outlook for Feb. 17-23, 2018.” American Meteor Society. Feb. 16, 2018.
Available @ https://www.amsmeteors.org/2018/02/meteor-activity-outlook-for-february-17-23-2018/

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

McBeath, Alastair. “α-Centaurids (102 ACE).” 2016 Meteor Shower Calendar > 3. January to March: 4.
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Ptolemy (Claudius Ptolemaeus). “Constellation of the Centaur: Configurations.” The Almagest, Book VIII: 257. Translated by R. Catesby Taliaferro. Chicago, IL; London, England; Toronto, Canada; Geneva, Switzerland; Sydney, Australia; Tokyo, Japan; Manila, the Philippines: Encyclopaedia Britannnica, Inc., 1952.

Rendtel, Jürgen. “α-Centaurids (102 ACE).” 2018 Meteor Shower Calendar > 3. January to March: 5.
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2019 January Comae Berenicids Shower Earth’s Skies Jan. 20 to Jan. 27

Summary: The 2019 January Comae Berenicids shower Earth’s skies Jan. 20 to Jan. 27, the shower’s annual activity dates, with midpoint peaking Jan. 23 to 24.

January Comae Berenicid meteor shower appears to radiate from an area to the west of Diadem (Alpha Comae Berenices) and Vindemiatrix (Epsilon Virginis); Coma Berenices Hair of Berenice 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 2019 January Comae Berenicids shower Earth’s skies Sunday, Jan. 20, to Sunday, Jan. 27, the meteor shower’s annual activity dates, with an expected midpoint peak Wednesday, Jan. 23, to Thursday, Jan. 24.

Robert Lunsford, the American Meteor Society’s Meteor Activity Outlook weekly columnist, places best viewing during pre-dawn hours. The January Comae Berenicid shower’s radiant (apparent point of origin) is positioned well above the horizon before midnight local standard time. Best viewing begins around 3 a.m. local standard time.

Lunsford describes the January Comae Berenicid meteors as swift-moving. Entry velocity during the meteors’ encounter with Earth’s atmosphere is 64 kilometers per second (39.7 miles per second).

The January Comae Berenicids are visible in both the Northern and Southern Hemispheres. Lunsford predicts an hourly rate of less than one at all viewing locations.

The IMO (International Meteor Organization) Video Meteor Network’s report for January 2013 tallied more than 13,000 meteors from 71 cameras during observing time of nearly 5,000 hours. The report assigned “almost 400 meteors” to the January Comae Berenicids. During the shower’s activity dates between Jan. 21 and Jan. 27, the report found that “there is no stronger meteor source in the sky.”

The January Comae Berenicid meteor shower’s name reflects an apparent point of origin in Coma Berenices the Hair of Berenice constellation. The shower’s meteors appear to radiate from the constellation’s southeastern region, near Virgo the Virgin constellation’s northwestern boundary. Lunsford places the January Comae Berenicid radiant during peak activity at five degrees southwest of Coma Berenices’ Diadem (Alpha Comae Berenices) and five degrees northwest of Virgo’s Vindemiatrix (Epsilon Virginis).

Alpha Comae Berenices (α Comae Berenices; Alf Com, α Com) is the second brightest star in the not-so-bright constellation of Coma Berenices. The bluish fourth magnitude star is actually a binary, comprising two components designated as Alpha Comae Berenices A, known traditionally as Diadem, and Alpha Comae Berenices B. Diadem’s traditional name reflects the binary star’s representation of the crown worn by Queen Berenice.

Epsilon Virginis (ε Virginis; Epsilon Vir, ε Vir) is the third brightest star in constellation Virgo, which reigns as the second largest constellation in Earth’s sky and as the largest of the 12 zodiacal constellations. The third magnitude, yellowish-hued star marks Virgo the Virgin’s right forearm or wing.

Epsilon Virginis is known as traditionally as Vindemiatrix (from Latin for feminine grape gatherer) or Vindemiator (from Latin for male grape gatherer). Dr. Mohammad Heydari-Malayeri, astrophysicist at l’Observatoire de Paris, suggests that the star’s traditional name derives from its first visibility at the time of grape harvesting.

Ancient Greece and ancient Egypt’s Berenice II (ca. 267/266-221 BCE) is the namesake of Coma Berenices constellation. She was born into the ruling family of the Greek colony of Cyrenaica (Cyrene) in North Africa (modern-day eastern coastal Libya) and succeeded her father, King Magnus of Crenaica (ca. 320-250 BCE). She became queen and co-regent of Egypt through her second husband, Ptolemy III Euergetes (284-222 BCE), Egypt’s third Ptolemaic ruler. Constellation Coma Berenices memorializes the queen’s votive offering of her long, amber hair on Aphrodite’s altar for her husband’s victory in the Third Syrian War (246-241 BCE).

The January Comae Berenicid meteor shower’s parent body is undetermined. A possible candidate is Comet Lowe, designed as comet 1913 I. Danish and American meteor astronomer Peter Jenniskens describes Comet 1913 I (Lowe) as an “intrinsically bright comet” in Meteor Showers and Their Parent Comets (2006). Jenniskens deems the identification of Comet Lowe as the parent body of the January Comae Berenicid shower’s retrograde-orbiting meteoroids as “. . . likely; if indeed the comet exists.”

The problem with Comet Lowe traces to errors in the discoverer’s telegraphed announcement, received Jan. 7, 1913, by South Australian government astronomer George Frederick Dodwell (Feb. 13, 1879-Aug. 10, 1963) at Australia’s Adelaide Observatory. Dodwell noted that B. Lowe erred in calculating the comet’s positions by way of the celestial coordinate system of right ascension (geographic longitude’s celestial equivalent) and declination (geographic latitude’s celestial equivalent).

Lowe used a 3-inch telescope for his observations. He noted that the comet was not a naked eye object and could not be discerned with field glasses. Through his telescope, the comet was “distinct, although small” and had a tail.

Lowe’s discovery happened Dec. 31, 1912, at 3 a.m. He first saw the comet near Spica in Virgo the Virgin constellation. Subsequent observations on Jan. 3, 5, 6 and 9 in 1913 revealed the comet’s progress through Hydra the Water Snake and Scorpio the Scorpion constellations and movement toward the Milky Way.

The takeaways for the 2019 January Comae Berenicids, which shower Earth’s skies annually from Jan. 20 to Jan. 27, are that the peak of shower’s swiftly moving meteors occurs Jan. 23 to Jan. 24 and that the shower’s parent body might be mysterious Comet 1913 I (Lowe).

fragment of a faience vase with depiction of Berenike (Berenice) II of Egypt, namesake of Coma Berenices constellation, Berenike II of Egypt, created during the reign of Ptolemy III Euergetes and Berenike II; vase originating from Egypt's Alexandra region; Metropolitan Museum of Art, Gallery 134 (Arts under the Ptolemies 2): Public Domain, via Metropolitan Museum of Art

Acknowledgment

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

Image credits:

January Comae Berenicid meteor shower appears to radiate from an area to the west of Diadem (Alpha Comae Berenices) and Vindemiatrix (Epsilon Virginis); Coma Berenices Hair of Berenice 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

fragment of a faience vase with depiction of Berenike (Berenice) II of Egypt, namesake of Coma Berenices constellation, Berenike II of Egypt, created during the reign of Ptolemy III Euergetes and Berenike II; vase originating from Egypt's Alexandra region; Metropolitan Museum of Art, Gallery 134 (Arts under the Ptolemies 2): Public Domain, via Metropolitan Museum of Art @ https://www.metmuseum.org/art/collection/search/551799

For further information:

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“00090 JCO January Comae Berenicids.” IAU (International Astronomical Union) Meteor Data Center > List of All Meteor Showers.
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Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1954AJ.....59..201W.pdf

Viljev, M. (Mikhail). Komet 1912 d (Lowe).” Astronomische Nachrichten, vol. 195, issue 20 (1913): 415-416. DOI: 10.1002/asna.19131952006.
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://adsbit.harvard.edu/full/seri/AN.../0195//0000225.000.html
Available via Wiley Online Library @ https://onlinelibrary.wiley.com/toc/15213994/195/20

Viljev, M. (Mikhail). “Zur Bahnbestimmung des Kometen 1912 d (Lowe).” Astronomische Nachrichten, vol. 195, issue 10 (1913): 107. DOI: 10.1002/asna.19131950506.
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://articles.adsabs.harvard.edu/full/1913AN....195..107V
Available via Wiley Online Library @ https://onlinelibrary.wiley.com/toc/15213994/195/10

Whipple, Fred L. “Photographic Meteor Orbits and Their Distribution in Space.” Astronomical Journal, vol. 59, no. 6 (July 1954 ~ No. 1218): 201-217 (204 and 211).
Available via Harvard ADSABS (NASA Astrophysics Data System Abstracts) @ http://adsbit.harvard.edu/full/seri/AJ.../0059//0000001,016.html

Whitworth, N. John. “Coma Berenicids Meteor Shower.” Universe Guide > Meteor Showers.
Available @ https://www.universeguide.com/meteorshower/comaberenicids

Wislez, Jean-Marc. “The 1999 International Meteor Conference Frasso Sabino, Italy, September 23-26, 1999.” WGN, vol. 27, no. 5 (October 1999): 223-225.
Available via IMO @ https://www.imo.net/publications/wgn/

Delta Cancrids Shower Night Sky From Dec. 14 to Feb. 14

Summary: The Delta Cancrids shower the night sky from mid-December to mid-February and peak in mid-January during the main shower.

The Delta Cancrids appear to radiate from the constellation of Cancer the Crab; Cancer, as viewed with unaided eyes, with added connecting lines: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons

As a minor meteor shower, the Delta Cancrids appear Dec. 14, shoot the main shower from Jan. 1 to Jan. 24, peak around Jan. 15 to 17, and finish Feb. 14.

The peak for 2016 occurs between Sunday evening, Jan. 17, and pre-dawn Monday, Jan. 18. The shower contends with the Moon’s first quarter phase. With visibility at 57 percent, the first quarter moon may block viewing of the meteor shower’s shooting stars. Viewing improves after the Moon’s setting around midnight.

The Delta Cancrids’ minor show barely ups its low hourly rate, known in astronomy as Zenithal Hourly Rate (ZHR), for its peak in mid-January. Normal rates that flag at less than one meteor per hour increase to three or four per hour during the Delta Cancrids’ peak. According to the International Meteor Organization, Delta Cancrid meteors enter Earth’s atmosphere at speeds of 28 kilometers per second (over 62,634 miles per hour). Their speed approximates the Earth’s orbital speed of about 30 kilometers per second (67,000 miles per hour).

The constellation of Cancer the Crab serves as apparent, though not actual, host for the Delta Cancrids. The meteor shower’s name reflects the Crab constellation as the radiant, or apparent point of origin, for Delta Cancrid shooting stars. The name also recognizes orange giant star Delta Cancri (δ Cnc, δ Cancri) as the specific radiant in the constellation’s center. Traditionally known in Latin as Asellus Australis (“southern donkey colt”), Delta Cancri is Cancer’s central star. Delta Cancri marks the southern flank of Praesepe, an open, or galactic, star cluster also known as the Beehive Cluster.

Cancer’s prime visibility in the Northern Hemisphere, from late autumn to spring, offers a convenient context for the Delta Cancrid meteor showers. Cancer rises above the eastern horizon in the early evening as the Sun sets, shines overhead after midnight and sets in the west as the Sun rises in the eastern skies.

Meteor shower activity, however, is not confined to the sector of the sky in which namesake constellations are located. The shower only appears to originate in the namesake constellation from the perspective of Earthlings. The misperception is helpful for identifying different meteor showers that overlap. Tracing shooting stars back to their apparent constellationary radiant solves the mystery of which known meteor shower is which.

Meteor showers flare as Earth’s orbit passes through streams of debris released from a parent comet. The source of the Delta Cancrids is presently unknown.

The takeaway for the Delta Cancrids is that classification as a minor meteor shower should not discourage viewers. Minor meteor showers may lack the busyness of the major showers but they still entertain.

The clarity of winter’s skies frame Delta Cancrids’ shooting stars. With their appearance over two Northern Hemisphere winter months, the Delta Cancrids ring out the old year, ring in the new year and take leave on Valentine’s Day.

Delta Cancri (δ Cancri), known traditionally as Asellus Australis ("southern donkey colt"), lies at the center of Cancer the Crab constellation and hosts the Northern Hemisphere's Delta Cancrids as the meteor shower's radiant; red dashed line = ecliptic; yellow dashed line = constellation boundaries; blue smudges = Milky Way areas of different brightness; Cancer the Crab constellation created by PP3 celestial map generation program: Torsten Bronger, CC BY SA 3.0 Unported, 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:

The Delta Cancrids appear to radiate from the constellation of Cancer the Crab; Cancer, as viewed with unaided eyes, with added connecting lines: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:CancerCC_cropped.jpg

Delta Cancri (δ Cancri), known traditionally as Asellus Australis ("southern donkey colt"), lies at the center of Cancer the Crab constellation and hosts the Northern Hemisphere's Delta Cancrids as the meteor shower's radiant; red dashed line = ecliptic; yellow dashed line = constellation boundaries; blue smudges = Milky Way areas of different brightness; Cancer the Crab constellation created by PP3 celestial map generation program: Torsten Bronger, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Cancer_constellation_map.png

For further information:

“Cancer Constellation.” SolarSystemQuick > Constellations.
Available @ http://www.solarsystemquick.com/universe/cancer-constellation.htm

“January 2016 Sky Events Calendar.” Arkansas Sky Observatory >ASO Sky Events Calendars. Dec. 30, 2015.
Available @ http://www.arksky.org/smf/index.php?topic=2660.0;prev_next=next

“January to March.” International Meteor Organization > Meteor Science > Meteor Shower Calendar > IMO Meteor Shower Calendar 2004.”
Available @ http://www.imo.net/calendar/2004/winter?PHPSESSID=1fb18a1401ae2541b2a2c.

Kronk, Gary W. Meteor Showers: An Annotated Catalogue. The Patrick Moore Practical Astronomy Series. 2nd ed. New York: Springer Science + Business Media, 2014.

Lunsford, Robert. “Meteor Activity Outlook for January 16-22, 2016.” American Meteor Society > Meteor Showers. Jan. 15, 2016.
Available @ http://www.amsmeteors.org/2016/01/meteor-activity-outlook-for-january-16-22-2016/

McClure, Bruce. “Cancer? Here’s your constellation.” EarthSky > Tonight > Constellations. March 7, 2014.
Available @ http://earthsky.org/constellations/cancer-heres-your-constellation

Rho Geminids Maximize Friday, Jan. 8, and Again Thursday, Jan. 21

Summary: The Rho Geminids maximize Friday, Jan. 8, and again Thursday, Jan. 21, during their month-long shower from the end of December to the end of January.

The radiant point for the Rho Geminids is in the constellation Gemini ~ Gemini, as viewed with unaided eyes, with added connecting lines: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons

Appearing as a minor meteor shower from Monday, Dec. 28, to Thursday, Jan. 28, the Rho Geminids maximize on Friday, Jan. 8, and then shoot stars in a secondary maximum of peak hourly rates, known in astronomy as zenithal hourly rate (ZHR), on Thursday, Jan. 21.

The Rho Geminid meteor shower’s secondary maximum on Jan. 21 has to contend with lunar brightness of the waxing gibbous phase, with over 90 percent visibility, and extensive cloud cover. The graphical sky cover forecast issued by the National Oceanic and Atmospheric Administration’s National Weather Service for the CONUS (48 contiguous states) Area for Jan. 21, the date of the Rho Geminids’ secondary maximum, indicates sky cover over the Pacific Northwest and much of the central and eastern United States. Clear skies are expected over Florida, the Southwest, and sections of the mid-Atlantic states and of New England.

Members of the Italian Meteoric Association first detected the Rho Geminids as eight meteors seeming to shoot out from the constellation Gemini’s northwestern sector. The Italian meteor shower trackers made their discovery in January 1872. Subsequent observations were made by British amateur astronomer William Frederick Denning in 1897, German astronomer Cuno Hoffmeister in 1921 and 1931, and Estonian astronomer/astrophysicist Ernst Julius Öpik in 1933.

Astronomers Gerald Stanley Hawkins and Richard B. Southworth were first to suggest the production of a regular meteor shower by the recurring January stream. In 1963, they identified four meteors from meteor orbits photographed from 1952 to 1954 by the Harvard Meteor Program as representing the suggested shower.

Meteors journey across the sky every night. Nightly meteor activity links either to a known major or minor meteor shower or to sporadic meteors with no known meteor shower associations. A variety of factors accounts for minor meteor showers such as the Rho Geminids. Small amounts of debris from the parent comet produce minor activity as Earth passes through the meteor stream. Planetary and solar forces have thinned old meteor showers by depleting or diffusing their streams. New meteor showers are in the early stages of receiving debris from their parent comets. A meteor shower’s slight grazing with Earth’s orbit also produces minor activity.

The constellation of Gemini the Twins serves as namesake of the Rho Geminids because the meteor shower appears to radiate from near Castor in Gemini’s western regions. The Rho Geminids share their constellatory radiant with one of the year’s most popular major meteor showers, December’s Geminids. The Heavenly Twins’ constellation also is linked with other minor meteor showers, such as October’s Epsilon Geminids.

Although their flashy flights appear to trace back to their namesake constellations, meteor showers are not restricted in their range. The namesake constellation serves as a convenient reference point, not as the actual point of origin for the meteor shower.

Although minor meteor showers are not as flashy as major meteor showers, their sedate show is worthwhile. The Rho Geminids offer the double excitement of two maximums. Viewers who miss the first maximum on Jan. 8 have a second chance with the second maximum on Jan. 21. Those who catch both maximums double their enjoyment of the Rho Geminids.

A bonus of watching for the Rho Geminids is easy viewing of Gemini. The meteor shower's annual appearance in January coincides with Gemini's favorable placement high overhead in the night sky.

Castor and Pollux, the Heavenly Twins: ca. 1825 depiction of Gemini by British cartographer and engraver Sidney Hall (1788-1831); Library of Congress Prints and Photographs Division, Washington DC: Library of Congress Prints and Photographs Division, Public Domain, 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:

The radiant point for the Rho Geminids is in the constellation Gemini ~ Gemini, as viewed with unaided eyes, with added connecting lines: Till Credner, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:GeminiCC.jpg

Castor and Pollux, the Heavenly Twins: ca. 1825 depiction of Gemini by British cartographer and engraver Sidney Hall (1788-1831); Library of Congress Prints and Photographs Division, Washington DC: Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Sidney_Hall_-_Urania's_Mirror_-_Gemini.jpg; No known restrictions on publication in the U.S., via Library of Congress Prints & Photographs Online Catalog (PPOC) @ https://www.loc.gov/pictures/item/2002695511/

For further information:

Denning, William F. Telescopic Work for Starlight Evenings. London: Taylor and Francis, 1891.
Available via Internet Archive @ https://archive.org/stream/telescopicworkfo00dennrich#page/n5/mode/2up

Kronk, Gary. "Observing the Geminids." Meteor Showers Online.
Available @ http://meteorshowersonline.com/geminids.html

Marriner, Derdriu. "2015 Geminids Peak Monday, Dec. 14, With After-Peak High Dec. 15." Earth and Space News. Monday, Dec. 14, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/12/geminids-peak-december-14-peak-high-december-15.html

Marriner, Derdriu. “January’s Quadrantids Kick Off New Year Shooting Star Show Lineup.” Earth and Space News. Monday, Jan. 4, 2016.
Available @ https://earth-and-space-news.blogspot.com/2015/12/2015-geminids-peak-on-december-14-with.html

McClure, Bruce. “Gemini? Here’s your constellation.” EarthSky > Tonight > Constellations. Feburary 3, 2015.
Available @ http://earthsky.org/constellations/gemini-heres-your-constellation

“The night sky for January 2016.” The Jodcast. Jan. 9, 2016.
Available @ http://www.jodcast.net/sky/

Reynolds, Mike D. Falling Stars: A Guide to Meteors and Meteorites. Mechanicsburg PA: Stackpole Books, 2001.