Star Stars · In Canes Venatici
Cor Caroli
Cor Caroli, α² Canum Venaticorum, is a white star in Canes Venatici: the 157th brightest star in the night sky.
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- Constellation
- Canes Venatici
- Designation
- α² Canum Venaticorum
- Apparent magnitude
- 2.89 · 157th brightest star in the night sky
- Spectral class
- A0spe
- Distance
- 115 light-years
- Highest at midnight
- early April
- Position (J2000)
- RA 12h 56m · Dec +38° 19′
A white star, around 10,000 K, like Sirius and Vega. About 28× brighter than the faintest star the eye can see. Gives off about 73 times the Sun's visible light. The light you are seeing left around 1911.
When to see it
On the night of Sat 3 Apr 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 13:45 | 01:09 · 77° | 12:33 |
| New York EDT | 16:15 | 01:04 · 87° | 09:52 |
| Singapore GMT+8 | 19:11 | 01:14 · 53° | 07:18 |
| Sydney GMT+11 | 21:13 | 01:05 · 18° | 03:57 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 78° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 17° up in the north.
- When is the best time of year to see it?
- Around early April, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early July it is highest in the early evening, and in early January not until the hours before dawn.
- How far away is it, and how bright?
- It is 115 light-years away, and shines at magnitude 2.89 in our sky. From that far, the Sun would be a star of magnitude 7.5: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.89 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Alkaid: Cor Caroli is 14° south-west of it, a fist and a half at arm’s length.
Look for
From 50° north it climbs to 78°; from 35° north it climbs to 87°; from the equator it climbs to 52°; from 35° south it climbs to 17°.
Science
Cor Caroli’s surface is about 10,000 K, some 4,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 290 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 0.2, about as bright as Rigel looks to us.
Did you know
Against Alkaid, the brighter star the hop starts from: Alkaid looks 2.6 times as bright as Cor Caroli in our sky; Alkaid is 104 light-years away and Cor Caroli 115 light-years, so side by side Alkaid would give off 2.1 times as much light as Cor Caroli.
Science
Cor Caroli is the 60th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Alkaid, about 29 light-years from it; on our sky the two are 14° apart.
Look for
The Sun passes 40° south of Cor Caroli around early October, 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 21 hours a day, from 35° north about 16 and from 35° south about 7. It is 79° from the plane of the Milky Way, well away from the band.