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The largest constellation of all, representing a water-snake. Hydra meanders from the celestial equator into the southern celestial hemisphere, and is over 100° long. Its brightest star is Alphard (Alpha Hydrae). R Hydrae is a Mira star that varies between magnitudes 4 and 11 every 390 days, and U Hydrae is a semiregular variable that ranges between magnitudes 4.3 and 6.5. M48 is a 6th-magnitude open star cluster visible in binoculars, and M83 is an 8th-magnitude spiral galaxy. NGC 3242 is a planetary nebula known as the Ghost of Jupiter.

Subjects: Astronomy and Astrophysics.

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