Constellation Data

Name: GEMINI Translation: Twins Abbreviation: Gem Genitive: Geminorum Size: 30 Regions: Zodiac RA: 7 hours Decl: +25 degrees Season: Winter Midnight Culmination: January 5 Pages where GEMINI is discussed in Chet Raymo's 365 Starry Nights: 3,25,31-34,40,45

What is the Genitive form? What is Right Ascension (RA)? Is this constellation ever visible from my latitude? What is Declination? Where should I look for a constellation on a date before or after its midnight culmination? What is Midnight Culmination?

Skylore

To the Greeks, Castor and Pollux were the twin sons of Zeus and the mortal woman Leda. Homer's Iliad tells how the beauty of their sister Helen "launched a thousand ships" in the Trojan war. After Castor's death, Pollux was overwhelmed with grief, and wanted to share his immortality with his twin. Finally Zeus reunited them by placing them together in the heavens. With the oath "By Jiminy," sailors revered the Gemini twins as the Protectors of ships.

The Geminids meteor shower, around October 19.

Description

Look for the two bright stars, Castor and Pollux, which form one vertex of the Winter Hexagon. Castor is closer to Capella, in Auriga on the north; and Pollus is closer to Procyon, in Canis Minor on the south. Cancer and Leo.htm">Leo lie to the east.

Legend: In the constellation chart above...
• Star colors represent their spectral types (even for double stars).
• Bright star labels are yellow; significant other stars are labelled in magenta.
• The size of each star indicates its relative magnitude.
• Constellation names are light blue.
• Grid lines represent either 10 degree intervals of declination above or below the equator, or intervals of one hour (=15 degrees) of right ascension (measured along the equator).
• Messier object numbers are pink.
• Galaxies are ovals: blue if spiral, yellow if elliptical, light blue if irregular.
• Globular clusters are gold starbursts.
• Open clusters are dotted white circles.
• Planetary nebula are green diamonds.
• Bright nebula are magenta squares.
• Dark nebula are grey rectangles.
• Green x's are x-ray sources.
• Purple O's with a diagonal slash through them are quasars.

Asterisms

Winter Hexagon (see Taurus).

What is an Asterism?

Special Stars

The two bright stars Castor and Pollux together form one vertex of the Winter Hexagon. Castor, on the Capella side, is actually six stars in one, ceaselessly revolving around one another in an intricately-choreographed cosmic dance. Pollux is the nearer of the twins, about 35 light years from the sun. Castor lies at a distance of 45 light years, and is a little less bright than Pollux.

Table of 25 Brightest Stars.
What is apparent stellar magnitude?

Star Clusters

M35 (Galactic cluster), mag. 5.6.

What are Star Clusters?

Discussed in these Shows

• Cowboy Astronomer
• Starstruck Tonight

©1997 Welcome to the Basic Celestial Phenomena web site. To provide explanations of basic observational astronomy to students, teachers, families, and visitors to planetariums these pages have been written by an ex-OBU Planetarium Director, Kerry Magruder; the OBU Natural Sciences Coordinator, Mike Keas; and some of the students who work in the OBU planetarium.

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