Constellation Data

Name: HYDRA Translation: Sea serpent Abbreviation: Hya Genitive: Hydrae Size: 1 RA: 11 hours Decl: -15 degrees Season: Spring Midnight Culmination: March 15 Pages where HYDRA is discussed in Chet Raymo's 365 Starry Nights: 38,43,52,53

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

Hercules was sent to kill Hydra, a sea monster which possessed the terrifying ability, whenever a head was cut off, to grow two heads in its place.

Cicero, De natura deorum, II.110, trans. of Phenomena by Aratos of Soli (ca. 220 B.C.):
Here Hydra rises from the nether realms,
And in her midmost coil the Wine-bowl (Crater) gleams,
While pressing at her tail the feathered Crow (Corvus)
Pecks with his beak; and here, hard by the Twins,
The Hound's forerunner, in Greek named Prokyon.

Description

The largest and longest of the constellations, stretching from Cancer to Libra. Its brightest star is Alphard, with an orangish tint. Two constellations ride it, Crater (cup) and Corvus (crow).

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.

Star Clusters

M48 (Galactic cluster), mag. 6.0.

M68 (Globular cluster), mag. 8.2.

What are Star Clusters?

Galaxies

M83 (Spiral galaxy), mag. 7.6.

What are Galaxies?
Table of Messier Objects.
What is apparent Magnitude?

Discussed in these Shows

• 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.

The source for the logo is not a medieval woodcut!

These web pages may be printed, copied, and distributed for educational use by any non-profit educational group so long as they are not edited or altered in any way, nor distributed for profit, nor repackaged or incorporated into any other medium or product, and so long as full credit is given to Kerry Magruder.

If you find a link that does not work, please tell us which link does not work--and which page you are on. Contact us by Email with general inquiries or suggestions. Thank you.

Basic Celestial Phenomena	Constellations	Not a Medieval Woodcut	Planetarium pages
EarthVisions.net	Geology	History of Science