Hydrus
What is Hydrus?
Constellations· Southern summer · a triangle between the two Magellanic Clouds. A small water snake, easily confused with Hydra. It forms a triangle between the two Magellanic Clouds, and beta Hydri — an aging Sun-like neighbour — is the brightest star close to the south celestial pole.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Hydrus is in your sky right now: https://nowsky.org/solar/sky?sel=con:Hydrus — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Beta Hydri | 2.8 |
| Alpha Hydri | 2.9 |
| Gamma Hydri | 3.2 |
The 3 brightest of the 3 stars used in the figure (2 lines). Lower magnitude means brighter.
Deep-sky objects near this constellation
Constellation basics
| Season | Nov–Jan evenings; not visible from Korea |
|---|---|
| Brightest star | β Hydri, mag 2.8 |
| How to find | between Achernar and the Small Magellanic Cloud |
| Area rank | 61st of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Hydrus?
- Nov–Jan evenings; not visible from Korea.
- How do I find Hydrus?
- between Achernar and the Small Magellanic Cloud.
- What is the brightest star in Hydrus?
- Beta Hydri, magnitude 2.8.
- Where is Hydrus in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
The bridge of gas between the two Magellanic Clouds
Hydrus lies between the Large and Small Magellanic Clouds, and across the sky between them hangs an invisible bridge. The Magellanic Bridge, found by radio observation in 1963, is a band of neutral hydrogen joining the two galaxies, torn from the Small Cloud as the gravity of the Large Cloud pulled at it. Stars have since been confirmed forming within the gas.
The two galaxies have orbited each other and exchanged material for hundreds of millions of years, and on the far side of the bridge a longer tail of gas, the Magellanic Stream, trails across half the sky. The bridge in the direction of Hydrus is the nearest specimen of tidal interaction between galaxies. The constellation cannot be seen from Korea, but in southern photographs the darkness between the two clouds is in fact linked by gas.
The constellation in depth
Hydrus is one of the twelve southern constellations recorded by Dutch navigators in the 1590s and published in Bayer's atlas of 1603. Its name means 'small water snake', chosen to set it apart from the great northern Hydra — though the similar Latin names still cause confusion today. Its stars are modest, mostly of the third and fourth magnitude.
Beta Hydri, its brightest star, is a yellow subgiant 24 light-years away and about twice the Sun's age. Having nearly exhausted its hydrogen it is beginning to swell, which is why it is often cited as a preview of the Sun's future; at about 12° from the south celestial pole it is the nearest bright star to it. Alpha Hydri sits right beside Achernar.
At declinations of −58° to −82° it cannot be seen from Korea. In the southern hemisphere it rides high on November to January evenings alongside Achernar and the Small Magellanic Cloud. In the Sky view, set Cape Town or Sydney on a December evening to see the triangle between the two Clouds. With the constellation lines on, the triangle beside Achernar stands out immediately.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.