2018 December Phi Cassiopeiids Peak in First Full Week of December

Summary: The 2018 December Phi Cassiopeiids peak in the first full week of December as a minor meteor shower maximizing annually around Dec. 5.

Northern Hemisphere observers of the December Phi Cassiopeiids easily located Cassiopeia the Seated Queen constellation’s w-shaped asterism via the Big Dipper’s handle and the Little Dipper’s Polaris: Learn to Skywatch @Learntoskywatch via Facebook Jan. 19, 2017

The 2018 December Phi Cassiopeiids peak in the first full week of December as a minor meteor shower that occurs annually at the end of November and maximizes annually between Dec. 1 and Dec. 5.

Danish and American meteor astronomer Peter Jenniskens, who associates with NASA’s Ames Research Center and the Seti Institute as senior research scientist, is credited with discovering the December Phi Cassiopeiids via the NASA-funded CAMS (Cameras for Allsky Meteor Surveillance) project in 2012. He discovered the shower in the course of reducing and analyzing observations made during the first 2.5 years of the CAMS project’s operation. The observations stemmed from a 60-camera three-station video surveillance of the night sky in California’s San Francisco Bay Area.

Jenniskens describes the newly discovered shower as composed of “very slow meteors” in his article, “Mapping Meteoroid Orbits: New Meteor Showers Discovered,” published in Sky & Telescope’s September 2012 issue. He places the shower members’ entry velocity as 16.7 kilometers per second (37,400 miles per hour). Jenniskens identifies Cassiopeia the Seated Queen constellation as the new shower’s apparent point of origin, known as the radiant.

An incomplete profile still remains for the newly discovered December Phi Cassiopeiids. The shower’s parent body is unknown. Jenniskens suspects a Jupiter Family Comet (JFC) as the parent body for the December Phi Cassiopeiids. Jupiter Family Comets are characterized as having orbital periods of less than 20 years. The cometary group’s name acknowledges the influence of Jupiter’s gravity upon group members.

“From what I can tell, nobody has ever heard of it,” Jenniskens concludes. “It has been designated the December Phi Cassiopeiids (code DPC).”

American amateur astronomer Robert Lunsford, who writes weekly Meteor Activity Outlook columns for the American Meteor Society (AMS) and for the International Meteor Organization (IMO), predicts Monday, Dec. 4, as the peak date for the 2017 December Phi Cassiopeiids. The meteor shower’s 2017 activity dates run from Tuesday, Nov. 28, to Sunday, Dec. 10.

Lunsford’s activity report for Saturday, Nov. 25, to Friday, Dec. 1, 2017, points to the radiant’s location in southern Cassiopeia, at 2 degrees south of Alpha Cassiopeiae (α Cassiopeiae; Alpha Cas, α Cas). Alpha Cassiopeiae generally is considered as the Seated Queen’s brightest star. The multiple star system marks the apex of the sharply angled vee of the Queen’s w-shaped pattern of stars, known as an asterism.

Lunsford’s activity report for the 2016 December Phi Cassiopeiids gives Saturday, Nov. 26, through Monday, Dec. 5, as the shower’s 2016 activity range. He pinpoints peak as occurring Thursday, Dec. 1, “. . . when the radiant is located at 01:33 (023) +53.” The radiant’s location in southern Cassiopeia approximates 3 degrees southeast of Theta Cassiopeiae (θ Cassiopeiae; Theta Cas, θ Cas). Theta Cassiopeiae lies between the Seated Queen’s southeastern neighbor, Perseus the Hero constellation, and the sharply angled vee of the Queen’s w-shaped asterism.

Lunsford recommends around 8 p.m. local standard time as best viewing time. Cassiopeia the Seated Queen constellation appears high in Northern Hemisphere skies then. Lunsford notes that the radiant’s high northern location discourages visibility for Southern Hemisphere observers at locations south of the southern tropics.

The International Astronomical Union (IAU) designates the December Phi Cassiopeiids with the three-letter code of DPC. The meteor shower’s IAU unique number is 00446.

The 60-camera three station video surveillance that prompted the discovery of the December Phi Cassiopeiids detected a total of 60 newly identified meteor showers. Jennisken and nine CAMS-project participants identified the new showers in their article, CAMS Newly Detected Meteor Showers and the Sporadic Background, published in the March 1, 2016, issue of Icarus. The new showers comprise numbers 00427, 00445, 00446, 00506, 00507 and part of 00634 to 00750 in the IAU Working List of Meteor Showers.

The takeaway for the 2018 December Phi Cassiopeiids’ peak in the first full week of December is that the newly discovered meteor shower is observable in the Northern Hemisphere and also in the Southern Hemisphere at southern tropical latitudes.

Cassiopeia the Seated Queen constellation’s distinctive w-shaped asterism, with (bottom center) Theta Cassiopeia (θ Cassiopeiae), radiant for December Phi Cassoipeiids: Longway Planetarium ‏@LongwayP via Twitter Nov. 8, 2017

Acknowledgment

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

Image credits:

Northern Hemisphere observers of the December Phi Cassiopeiids easily located Cassiopeia the Seated Queen constellation’s w-shaped asterism via the Big Dipper’s handle and the Little Dipper’s Polaris: Learn to Skywatch @Learntoskywatch via Facebook Jan. 19, 2017, @ https://www.facebook.com/Learntoskywatch/photos/a.223850584681982.1073741828.223634834703557/333331490400557/

Cassiopeia the Seated Queen constellation’s distinctive w-shaped asterism, with (bottom center) Theta Cassiopeia (θ Cassiopeiae), radiant for December Phi Cassoipeiids: Longway Planetarium ‏@LongwayP via Twitter Nov. 8, 2017, @ https://twitter.com/LongwayP/status/928426923797176320

For further information:

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