Zaurak (Gamma Eridani)
Zaurak (Gamma Eridani) is a star in the constellation Eridanus, magnitude 2.9.
‘The boat’ of the celestial river: an ageing red giant that astronomers use as a standard for its kind.
Zaurak means ‘the boat’ — it is one of the Arabic words for one — and it floats in Eridanus, the celestial river. The star is a red giant near the end of its life. Its core is spent, and it now burns hydrogen and helium in separate shells around it, having swollen and cooled to a warm orange-red.
It is so typical of its kind that astronomers use it as a reference: Zaurak is a standard star for the M0 III spectral type, against which other red giants are compared. In 1960 observers found it flickering by a few hundredths of a magnitude, and in 1977 it was officially listed as a variable star — though nobody is sure what kind.
Nor is it alone. Data from the Gaia spacecraft revealed a small star, about a tenth of the Sun’s mass, travelling with Zaurak far out, and another red dwarf may hide much closer in, lost in the giant’s glare.
Zaurak (Gamma Eridani) is 200 light-years away: the light we see from it set off around 1825, 20 years before Neptune was discovered.
Did you know?
- First of the Celestial Meadows. Chinese astronomers placed Zaurak in Tiān Yuàn, the Celestial Meadows, a sweep of sixteen stars in Eridanus and Cetus. Zaurak is its first star.
- A ship named after it. The US Navy named a Crater-class cargo ship, USS Zaurak, after this star.
An orange-red 3rd-magnitude giant, the brightest star in the northern loop of Eridanus, about 20 degrees west-south-west of Rigel. Defocus binoculars slightly to bring out its warm orange.
When and where to see it
It is best placed in the evening sky around December, when it crosses the meridian at about 10 pm local time (around midnight in November). It can be seen from everywhere south of 76°N and never sets south of 76°S.
At its highest it stands 26° up from 50°N, 41° up from 35°N, 76° up from the equator, 69° up from 35°S.
Facts
- Type
- Star
- Constellation
- Eridanus
- Designations
- Gamma Eridani, γ Eri, 34 Eri, HR 1231, HD 25025, HIP 18543
- Magnitude
- 2.9
- Position
- RA 3h 58.0m, Dec −13° 31′ (J2000)
- Spectral type
- M0III-IIIb
- Colour
- orange-red (B−V 1.60)
- Distance
- 200 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Zaurak (Gamma Eridani) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.