Cursa (Beta Eridani)
Cursa (Beta Eridani) is a star in the constellation Eridanus, magnitude 2.8.
Orion’s footstool — a fast-spinning white star at the head of the River.
Orion has a footstool. Cursa takes its name from the Arabic Al Kursiyy al Jauzah, “the chair (or footstool) of the central one” — the central one being Orion. The name once belonged to a small group of stars beside the hunter’s foot: Cursa, two fainter stars of Eridanus and Tau Orionis.
Cursa is a hot white star near 8,360 K that has used up the hydrogen in its core. It spins at 196 kilometres per second or more — nearly 100 times the speed of the Sun’s equator.
Its light is not quite steady: it varies between magnitudes 2.72 and 2.80, and a particularly strong flare-up was reported in 1985. Its path through space suggests it may belong to the Ursa Major family of stars, though its colours hint that it could be an interloper.
Cursa (Beta Eridani) is 89 light-years away: the light we see from it set off in 1937, 7 years after Pluto was discovered.
Did you know?
- The Jade Well. Chinese astronomers saw Cursa and three nearby stars — two in Eridanus and one in Orion — as Yù Jǐng, the Jade Well. Cursa is its third star.
- A chance companion. An 11th-magnitude star 2 arcminutes away looks like a partner, but it is only an optical companion, lined up by chance.
A white star of magnitude 2.8 about 3½ degrees north-west of brilliant Rigel, where the long, winding River, Eridanus, begins. Compare the two: both look white, but Rigel is far brighter and slightly bluer.
When and where to see it
It is best placed in the evening sky around January, when it crosses the meridian at about 10 pm local time (around midnight in December). It can be seen from everywhere south of 85°N and never sets south of 85°S.
At its highest it stands 35° up from 50°N, 50° up from 35°N, 85° up from the equator, 60° up from 35°S.
Facts
- Type
- Star
- Constellation
- Eridanus
- Designations
- Beta Eridani, β Eri, 67 Eri, HR 1666, HD 33111, HIP 23875
- Magnitude
- 2.8
- Position
- RA 5h 7.8m, Dec −5° 5′ (J2000)
- Spectral type
- A3IV
- Colour
- white (B−V 0.13)
- Distance
- 89 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Cursa (Beta Eridani) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.