Star profile

Eta Hydrae

Variable star

3D likeness based on its real data · class B · ~15,000 K

What is Eta Hydrae

A massive blue star, seven times the Sun and nearly three thousand times more luminous, runs along the long serpentine body of the Water Snake at 587 light-years' distance. Its surface burns above 18,000 degrees; its rotation of around a hundred kilometres per second imprints a faint variable beat that for years left astronomers debating its classification. It is one of those hot, youthful beacons — barely 32 million years old — that pick out, with sharp precision, the serpentine geometry of the largest constellation in the sky.

Where it is and when to see it

Eta Hydrae lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is February, when it culminates around midnight.

From London it culminates about 42° above the horizon.
From New York it culminates about 53° above the horizon.
From Sydney it culminates about 53° above the horizon.

It can be seen from anywhere north of 87° S.

It ranks no. 16 in brightness among the 121 stars of Hydra in our catalogue. To find it, start from Alphard, the brightest: it lies about 16° away (a fist at arm's length covers about 10°).

The light you see today left it about 590 years ago.

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Astronomical data for Eta Hydrae

Constellation: Hydra
Apparent magnitude: 4.30
Distance: 586.7 light years
Coordinates (J2000): RA 130.806° · Dec 3.399°
Catalogue: HIP 42799 · HD 74280

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Other stars in Hydra

Hydra has 121 stars in Stelvia's catalogue. Here are a few of them.

See all 121 stars in Hydra