Algol
star · Perseus · 2.1ᵐ
The famous eclipsing variable: every 2.87 days a companion passes in front and the brightness drops by more than half for a few hours.
Notable facts
The light you see today left Algol around the year 1936.
About 37 times brighter than the faintest star visible to the naked eye.
In brief
Which constellation is Algol in?
Algol lies in Perseus.
Is Algol visible to the naked eye?
2.1ᵐ — visible to the naked eye (under dark skies).
When is the best time to observe Algol?
Best observed in November.
Data
- RA / Dec (J2000)
- 3h 08m · +40° 57′
- Type
- star
- Constellation
- Perseus
- How to observe
- 2.1ᵐ — visible to the naked eye (under dark skies)
- Spectral class
- B8V — blue-white star
- Absolute magnitude
- -0.1ᵐ
- Luminosity
- ≈95 × the Sun
- Distance
- ~90 light years
- Designation
- HIP 14576
Observing tip
Stars stay points at any magnification: aim your telescope for colour, brightness and companions, not detail.
Altitude above the horizon by latitude
| Latitude | Maximum altitude | Rise azimuth |
|---|---|---|
| +60° | 71° · never sets | — |
| +55° | 76° · never sets | — |
| +45° | 86° | 22° |
| +30° | 79° | 41° |
| 0° | 49° | 49° |
| −35° | 14° | 37° |
Geometric altitude at upper culmination, atmospheric refraction not included. Positive latitudes are in the northern hemisphere.
Culmination time by month
| Month | Culmination |
|---|---|
| January | 19:23 |
| February | 17:15 |
| March | 15:30 |
| April | 13:37 |
| May | 11:42 |
| June | 09:36 |
| July | 07:32 |
| August | 05:31 |
| September | 03:38 |
| October | 01:50 |
| November | 23:49 |
| December | 21:40 |
Upper culmination in local solar time — no time-zone or daylight-saving correction applied.