Star Stars · In Aquila
Okab
Okab, ζ Aquilae, is a white main-sequence star in Aquila: the 175th brightest star in the night sky.
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- Constellation
- Aquila
- Designation
- ζ Aquilae
- Apparent magnitude
- 2.99 · 175th brightest star in the night sky
- Spectral class
- A0Vn
- Distance
- 83.0 light-years
- Highest at midnight
- early July
- Position (J2000)
- RA 19h 05m · Dec +13° 52′
A white main-sequence star, around 10,000 K, like Sirius and Vega. About 25× brighter than the faintest star the eye can see. Gives off about 35 times the Sun's visible light. The light you are seeing left around 1943.
When to see it
On the night of Mon 5 Jul 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 18:00 | 01:12 · 52° | 08:23 |
| New York EDT | 18:18 | 01:06 · 63° | 07:54 |
| Singapore GMT+8 | 19:17 | 01:17 · 77° | 07:17 |
| Sydney GMT+10 | 18:47 | 00:08 · 42° | 05:29 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 54° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 41° up in the north.
- When is the best time of year to see it?
- Around early July, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by early October it is highest in the early evening, and in early April not until the hours before dawn.
- How far away is it, and how bright?
- It is 83.0 light-years away, and shines at magnitude 2.99 in our sky. From that far, the Sun would be a star of magnitude 6.8: 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 2.99 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Tarazed: Okab is 10° west of it, a fist at arm’s length.
Look for
From 50° north it climbs to 54°; from 35° north it climbs to 69°; from the equator it climbs to 76°; from 35° south it climbs to 41°.
Science
Okab’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 1.0, about as bright as Spica looks to us.
Did you know
Against Tarazed, the brighter star the hop starts from: Tarazed looks 1.3 times as bright as Okab in our sky; Tarazed is 395 light-years away and Okab 83 light-years, so side by side Tarazed would give off 29 times as much light as Okab.
Science
Okab is the 40th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Cebalrai, about 32 light-years from it; on our sky the two are 22° apart.
Look for
The Sun passes 36° south of Okab around early January, 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 3° from the plane of the Milky Way, inside the band a dark sky shows.