Star Stars · In Pegasus
Algenib
Algenib, γ Pegasi, is a blue-white subgiant in Pegasus: the 139th brightest star in the night sky.
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- Constellation
- Pegasus
- Designation
- γ Pegasi
- Apparent magnitude
- 2.83 · 139th brightest star in the night sky
- Spectral class
- B2IV
- Distance
- 392 light-years
- Highest at midnight
- late September
- Position (J2000)
- RA 00h 13m · Dec +15° 11′
A blue-white subgiant, around 26,000 K, like Rigel and Spica. About 29× brighter than the faintest star the eye can see. Gives off about 890 times the Sun's visible light. The light you are seeing left around 1634.
When to see it
On the night of Tue 21 Sep 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 17:53 | 01:12 · 54° | 08:32 |
| New York EDT | 18:13 | 01:07 · 65° | 08:00 |
| Singapore GMT+8 | 19:17 | 01:17 · 76° | 07:18 |
| Sydney GMT+10 | 18:52 | 00:08 · 41° | 05:25 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 55° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 40° up in the north.
- When is the best time of year to see it?
- Around late September, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late December it is highest in the early evening, and in late June not until the hours before dawn.
- How far away is it, and how bright?
- It is 392 light-years away, and shines at magnitude 2.83 in our sky. From that far, the Sun would be a star of magnitude 10.2: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.83 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Alpheratz: Algenib is 14° south of it, a fist and a half at arm’s length.
Look for
From 50° north it climbs to 55°; from 35° north it climbs to 70°; from the equator it climbs to 75°; from 35° south it climbs to 40°.
Science
Algenib’s surface is about 26,000 K, some 20,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 110 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 −2.6, brighter than Sirius, the brightest star in our sky.
Did you know
Against Alpheratz, the brighter star the hop starts from: Alpheratz looks 2.0 times as bright as Algenib in our sky, but Alpheratz is 97 light-years away and Algenib 392 light-years, so side by side Algenib would give off 8.1 times as much light as Alpheratz.
Science
Algenib is the 112th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Matar, about 220 light-years from it; on our sky the two are 26° apart.
Look for
The Sun passes 13° south of Algenib around late March, 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 14 hours a day, from 35° north about 13 and from 35° south about 11. It is 47° from the plane of the Milky Way, well away from the band.