Star Stars · In Capricornus
Deneb Algedi
Deneb Algedi, δ Capricorni, is a white star in Capricornus: the 147th brightest star in the night sky.
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- Constellation
- Capricornus
- Designation
- δ Capricorni
- Apparent magnitude
- 2.85 · 147th brightest star in the night sky
- Spectral class
- A5mF2 (IV)
- Distance
- 38.7 light-years
- Highest at midnight
- mid August
- Position (J2000)
- RA 21h 47m · Dec −16° 08′
A white star, around 8,800 K, like Sirius and Vega. About 29× brighter than the faintest star the eye can see. Gives off about 9 times the Sun's visible light. The light you are seeing left in 1987.
When to see it
On the night of Sun 15 Aug 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 20:37 | 01:12 · 22° | 05:47 |
| New York EDT | 20:05 | 01:07 · 33° | 06:09 |
| Singapore GMT+8 | 19:20 | 01:17 · 73° | 07:15 |
| Sydney GMT+10 | 17:25 | 00:08 · 72° | 06:51 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 24° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 71° up in the north.
- When is the best time of year to see it?
- Around mid August, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by mid November it is highest in the early evening, and in mid May not until the hours before dawn.
- How far away is it, and how bright?
- It is 38.7 light-years away, and shines at magnitude 2.85 in our sky. From that far, the Sun would be a star of magnitude 5.2: 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 2.85 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Fomalhaut: Deneb Algedi is 21° north-west of it, a spread hand at arm’s length.
Look for
From 50° north it climbs to 24°; from 35° north it climbs to 39°; from the equator it climbs to 74°; from 35° south it climbs to 71°.
Science
Deneb Algedi’s surface is about 8,800 K, some 3,000 K hotter than the Sun’s 5,772 K, so its light is strongest at about 330 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 2.5, about as bright as Aljanah looks to us.
Did you know
Against Fomalhaut, the brighter star the hop starts from: Fomalhaut looks 4.7 times as bright as Deneb Algedi in our sky; Fomalhaut is 25 light-years away and Deneb Algedi 39 light-years, so side by side Fomalhaut would give off 2.0 times as much light as Deneb Algedi.
Science
Deneb Algedi is the 14th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Fomalhaut, about 18 light-years from it; on our sky the two are 21° apart.
Look for
Deneb Algedi lies 2.6° south of the ecliptic, close enough to the Sun’s path that the Moon can pass in front of it and the planets pass near it. The Sun goes by around mid February, and for weeks either side it is lost in the glare. From 50° north it is above the horizon for about 9 hours a day, from 35° north about 10 and from 35° south about 14. It is 46° from the plane of the Milky Way, well away from the band.