Star Stars · In Eridanus
Cursa
Cursa, β Eridani, is a white giant in Eridanus: the 128th brightest star in the night sky.
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- Constellation
- Eridanus
- Designation
- β Eridani
- Apparent magnitude
- 2.78 · 128th brightest star in the night sky
- Spectral class
- A3IIIvar
- Distance
- 89.4 light-years
- Highest at midnight
- early December
- Position (J2000)
- RA 05h 08m · Dec −05° 05′
A white giant, around 9,300 K, like Sirius and Vega. About 31× brighter than the faintest star the eye can see. Gives off about 49 times the Sun's visible light. The light you are seeing left around 1937.
When to see it
On the night of Sat 5 Dec 2026, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT | 18:36 | 00:10 · 33° | 05:44 |
| New York EST | 18:23 | 00:05 · 44° | 05:46 |
| Singapore GMT+8 | 19:17 | 01:15 · 84° | 07:14 |
| Sydney GMT+11 | 18:54 | 01:06 · 61° | 07:19 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 35° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 60° up in the north.
- When is the best time of year to see it?
- Around early December, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early March it is highest in the early evening, and in early September not until the hours before dawn.
- How far away is it, and how bright?
- It is 89.4 light-years away, and shines at magnitude 2.78 in our sky. From that far, the Sun would be a star of magnitude 7.0: one you would need a dark country sky to see at all.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.78 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Rigel: Cursa is 3.5° north-west of it, three fingers at arm’s length.
Look for
From 50° north it climbs to 35°; from 35° north it climbs to 50°; from the equator it climbs to 85°; from 35° south it climbs to 60°.
Science
Cursa’s surface is about 9,300 K, some 3,500 K hotter than the Sun’s 5,772 K, so its light is strongest at about 310 nm, in the ultraviolet, past the violet end of what the eye can see, where the Sun’s is strongest at 500 nm. Moved to 33 light-years, the distance astronomers compare stars at, it would shine at magnitude 0.6, about as bright as Hadar looks to us.
Did you know
Against Rigel, the brighter star the hop starts from: Rigel looks 11 times as bright as Cursa in our sky; Rigel is 863 light-years away and Cursa 89 light-years, so side by side Rigel would give off 1,000 times as much light as Cursa.
Science
Cursa is the 48th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Aldebaran, about 38 light-years from it; on our sky the two are 23° apart.
Look for
The Sun passes 28° north of Cursa around early June, when it is highest at noon, in daylight: the weeks either side are its worst time of year. From 50° north it is above the horizon for about 11 hours a day, from 35° north about 11 and from 35° south about 12. It is 25° from the plane of the Milky Way.