Auriga the Charioteer Claims Capella as Night’s Sixth Brightest Star

Summary: Year-round Northern Hemisphere constellation Auriga the Charioteer claims Capella as night’s sixth brightest star.

Capella in Auriga the Charioteer (center) with Jupiter (upper left), March 30, 2014: Neal Simpson (Nohrmal), CC BY ND 2.0, via Flickr

Auriga the Charioteer claims Capella as night’s sixth brightest star during the year-round Northern Hemisphere constellation’s visible nightly sojourn.

Only five stars precede Capella in a ranking of apparent visual magnitudes of stars visible to Earthlings’ unaided eyes. Sirius, a binary system of two white stars in Canis Majoris, the Greater Dog constellation, claims first place. Canopus, a white-hued supergiant in Carina the Ship Keel constellation, holds second place. Third place goes to Alpha Centauri, a triple star system in Centaurus the Centaur constellation. Arcturus, a red giant star in Boötes the Herdsman constellation, is night’s fourth brightest star. In fifth place, just above Capella, is Vega, a blue-tinged white star in Lyra the Lyre constellation.

Capella holds fourth place among Northern Hemisphere nights’ brightest stars. Only Sirius, Arcturus and Vega outrank Capella in their respective first through third placements.

Yellowish white Capella (Latin: capella, “she-goat”) represents either the charioteer’s left shoulder or, according to second century C.E. astronomer Ptolemy, the heart of Amaltheia (Ancient Greek: μαλθασσω, malthasso, "to soften, to soothe"), the she-goat carried by the charioteer. An elongated triangle of stars (Epsilon Aurigae, Zeta Aurigae, Eta Aurigae) below Capella usually indicate two or three goat kids resting on the charioteer’s left wrist.

Located at a distance of 42.2 light years, Capella is actually a star system consisting of two binary pairs of stars. The main pair comprises luminous, yellow giants lying less than 100 million kilometers apart. Capella Ab completes a tight circular orbit of Capella Aa every 104.02 days. The second pair comprises dim red dwarf stars orbiting about a light year away from the first pair.

Capella’s astronomical designation is Alpha Aurigae (α Aurigae; Alpha Aur; α Aur). The designation uses alpha, the first letter of the Greek alphabet, to indicate Capella’s status as the constellation’s brightest star (“first of Auriga”).

Auriga occupies the upper quarter of the size-ranked list of modern astronomy’s 88 official constellations. With a solid angle area of 657.438 square degrees, Auriga rates as the 21st largest constellation. Auriga’s area is over half that of Hydra, the largest of the 88 official constellations. Hydra secures first place with a solid angle area of 1,302.844 square degrees.

The charioteer constellation lies in the plane of the northern Milky Way. Neighboring constellations in the northern sky comprise Camelopardalis the Giraffe to the north, Perseus to the west, Taurus the Bull to the south, Gemini the Twins to the southeast and the Lynx to the east. Dubhe and Merak, marking the front of the Big Dipper asterism’s bowl in Ursa Major the Great Bear constellation, serve as pointer stars for locating Capella and Auriga the Charioteer.

Easy visibility of Auriga the Charioteer occurs primarily northward of the Northern Hemisphere’s mid-latitudes, where the five-sided constellation numbers among northern circumpolar constellations. Southward from lower northern to lower southern latitudes, Auriga increasingly hugs the northern horizon.

In addition to inclusion in Auriga the Charioteer constellation, Capella participates in a hexagon asterism that usually is prominent from December to March. The asterism is known as the Winter Hexagon in the Northern Hemisphere and as the Summer Hexagon in the Southern Hemisphere.

Six constellations contribute their brightest stars to the hexagon asterism. Aldebaran in Taurus, Rigel in Orion the Hunter, Sirius in Canis Major, Procyon in Canis Minor (“Lesser Dog”) and Pollux in Gemini the Twins join Capella as vertex, or angle, placeholders.

The takeaway for Auriga the Charioteer’s ownership of Capella, night’s sixth brightest star, is the mutual benefit of easy findability of both the five-sided constellation and its brightest star.

Auriga (center left) and neighbors, Inglis Falls, Owen Sound, southwestern Ontario, Canada, Nov. 4, 2013: Northern Lights Graffiti Crew, CC BY 2.0, via Flickr

Acknowledgment

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

Image credits:

Capella in Auriga the Charioteer (center) with Jupiter (upper left), March 30, 2014: Neal Simpson (Nohrmal), CC BY ND 2.0, via Flickr @ https://www.flickr.com/photos/nohrmal/13531269754/

Auriga and neighbors, Inglis Falls, Owen Sound, southwestern Ontario, Canada, Nov. 4, 2013: Northern Lights Graffiti Crew, CC BY 2.0, via Flickr @ https://www.flickr.com/photos/northernlightsgraffiticrew/10665864854/

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