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Sky-Tonight.com / Constellations / Hydra
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Observation Settings

Or select it on the map:
This Earth map fragment is intended to illustrate celestial motion across the sky, emphasizing both bearing and elevational perspectives. The map's center point corresponds to the transit, showcasing celestial objects at their highest point, while elevation gradually decreases towards the map edges. This dynamic representation offers insights into the changing positions of celestial bodies with a focus on their bearing and elevational trajectories.
Your location: Columbus, United States
Timezone:
Latitude:
39.9625
Longitude:
-83.0061

Hydra Constellation

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Hydra, the water snake, is the largest constellation, stretching across the southern and northern hemispheres. It represents a serpent, and its brightest star is Alphard.

Hydra (The Water Serpent)

Hydra is the largest constellation in the night sky, stretching across both the northern and southern celestial hemispheres. Representing a water serpent in mythology, Hydra is a sprawling constellation that winds across the heavens. Despite its size, Hydra has relatively few bright stars, making it less conspicuous than other large constellations. It is best observed during the spring months in the Northern Hemisphere.

Key Features

  • Bright Stars: Hydra contains several notable stars:
    • Alphard (Alpha Hydrae): The brightest star in Hydra, a solitary orange giant located about 177 light-years away. Its name means "the solitary one" in Arabic, reflecting its isolation in the constellation.
    • Zeta Hydrae: A yellow giant star situated approximately 167 light-years away, marking the serpent's "head."
    • Gamma Hydrae: Another bright star in the constellation, located about 132 light-years away.
  • Deep-Sky Objects: Hydra is home to several fascinating celestial objects:
    • Messier 48 (M48): An open cluster of stars located about 1,500 light-years away, visible with binoculars.
    • Messier 68 (M68): A globular cluster of stars located about 33,000 light-years away.
    • NGC 3242: Also known as the "Ghost of Jupiter," a planetary nebula resembling a giant planet in appearance.

Mythological Background

In Greek mythology, Hydra represents the Lernaean Hydra, a multi-headed serpent that Hercules was tasked to slay as one of his twelve labors. The Hydra was said to grow two heads for every one that was severed, making it nearly invincible. Hercules eventually defeated the creature by cauterizing the stumps of its heads to prevent regeneration.

The constellation is often depicted with Corvus, the crow, and Crater, the cup, both of which share a mythological connection to the Hydra in stories of Apollo.

Cultural Significance

Hydra's vast size and mythological associations have made it a subject of fascination for stargazers and storytellers throughout history. Its brightest star, Alphard, has been referenced in various cultural traditions, often symbolizing solitude and resilience.

Though its stars are mostly faint, Hydra’s rich array of deep-sky objects attracts astronomers, while its mythological ties ensure its place in cultural lore. The constellation serves as a reminder of the legends and challenges that connect humanity to the stars.

Hydra Rise and Set Timetable

TimeElevation
Hydra Rise16:23
Moon Rise, 93.2% illuminated17:5914°
Sunset20:3327°
Hydra Transit20:5827°
Civil sunset21:0527°
Astrosession begin21:4226°
Hydra Set01:33
Moon Set05:05-39°
Astrosession end05:14-40°

Track Hydra Position Throughout the Night

← Sat, 10 May 2025 →

Elevation (degrees)
Time
Altitude
Azimuth
Shift the map to change the time and observe Hydra changing position in the night sky.

Annual motion of Hydra

Time
DateSat, 10 May 2025
Twighlight start22:18
Twighlight end04:28
Twighlight duration6h 10m
Rise16:19
Set01:29
Elevation at transit27°
Transit time20:54
Equatorial coordinatesRA: 10h 38m 59s", Dec: -23° 09' 11s
Magnitude-
Constellation
The graph illustrates the annual visibility pattern of a Hydra, providing a comprehensive overview of its daily appearances and transit times throughout the year.
The graph is structured with the vertical axis showing the hours of the day, ranging from 12 AM to 12 AM the next day, while the horizontal axis spans each day of the year.
The reddish shaded area indicates the periods when the Hydra is above the horizon, visible to observers. The white line marks the times when the celestial object reaches its highest point in the sky each day, known as the transit.

Acknowledgements

We gratefully acknowledge the International Astronomical Union (IAU) for defining and standardizing the official constellation boundaries, which provide a consistent framework for celestial mapping.

Special thanks to Sky & Telescope Magazine and contributors Roger Sinnott and Rick Fienberg for their collaboration in producing the charts and tables. The constellation patterns, drawn by Alan MacRobert, were influenced by the work of H. A. Rey and thoughtfully adjusted to align with earlier traditions.