Hydra constellation
Hydra (the Water Snake) is a constellation in the southern sky, best seen in the evening in April. Its brightest star is Alphard (magnitude 1.98). Hydra covers 1,303 square degrees and is the 1st-largest of the 88 constellations.
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Detailed star map of Hydra
Facts
| Latin name | Hydra (genitive: Hydrae) |
|---|---|
| Abbreviation | Hya |
| Meaning | the Water Snake |
| Area | 1,303 square degrees (1st of 88) |
| Location | right ascension 11.0 h, declination −22° |
| Visible from | latitudes 54° N to 83° S (whole constellation) |
| Best month | April (at about 9 pm) |
| Brightest star | Alphard |
| Stars brighter than magnitude 6 | 127 |
| Named stars (IAU) | 6 |
| Messier objects | M48, M68, M83 |
| Neighbors | Antlia, Canis Minor, Centaurus, Cancer, Crater, Corvus, Leo, Libra, Monoceros, Puppis, Pyxis, Sextans, Virgo |
How to find Hydra
From 40° N (the USA, southern Europe, Japan) look south in April evenings: at about 9 pm Hydra stands highest, around 28° above the southern horizon. From 35° S (Australia, South Africa, Argentina) it is highest in the north, about 77° above the horizon. The months before and after (March and May) are also good: then it is up a couple of hours earlier or later.
Hydra borders Antlia, Canis Minor, Centaurus, Cancer, Crater, Corvus, Leo, Libra, Monoceros, Puppis, Pyxis, Sextans and Virgo.
Stars of Hydra
Hydra has 127 stars brighter than magnitude 6, the limit of the naked eye under a dark sky. These are the brightest:
| Star | Designation | Magnitude | Type | Distance |
|---|---|---|---|---|
| Alphard | α Hydrae | 1.98 | K3II-III | — |
| — | γ Hydrae | 3.0 | G8-IIIa | — |
| — | ν Hydrae | 3.11 | K2III | — |
| — | ζ Hydrae | 3.11 | G9II-III | — |
| — | π Hydrae | 3.27 | K2-III-IIIbFe-0.5 | — |
| Ashlesha | ε Hydrae | 3.38 | G5III | — |
| — | ξ Hydrae | 3.54 | G7III | — |
| — | λ Hydrae | 3.61 | K0IIICN1 | — |
| — | μ Hydrae | 3.81 | K4.5III | — |
| — | θ Hydrae | 3.88 | B9.5V | — |
| — | HR 3314 | 3.9 | A0V | — |
| Ukdah | ι Hydrae | 3.91 | K2.5III-IIIbBa0.3 | 253 ly |
Deep-sky objects in Hydra
Hydra contains 3 objects from Charles Messier's catalog:
- Messier 48 (M48): open cluster, 5.8 mag
- Messier 68 (M68): globular cluster, 8.0 mag
- Southern Pinwheel Galaxy (M83): spiral galaxy, 7.5 mag
Printable Hydra map and outline
A black and white version for printing and a plain outline of the Hydra figure, useful for school projects, worksheets and learning to recognize the shape.
History
Hydra is one of the 48 constellations listed by Ptolemy in the Almagest (2nd century AD). Its official boundary was drawn by Eugène Delporte for the International Astronomical Union in 1930.
Questions about Hydra
What is the brightest star in Hydra?
Alphard, at magnitude 1.98.
When can you see Hydra?
Hydra is best seen in the evening in April. The whole constellation is visible from latitudes between 54° N and 83° S.
How many stars are in Hydra?
127 stars in Hydra are brighter than magnitude 6 and can be seen with the naked eye under a dark sky; 6 of them have official IAU names.
What does Hydra mean?
Hydra means “the Water Snake” in Latin. Its abbreviation is Hya and the genitive, used in star names such as α Hydrae, is Hydrae.
