Star Stars · In Sagittarius
Kaus Australis
Kaus Australis, ε Sagittarii, is a blue-white giant in Sagittarius: the 37th brightest star in the night sky.
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- Constellation
- Sagittarius
- Designation
- ε Sagittarii
- Apparent magnitude
- 1.79 · 37th brightest star in the night sky
- Spectral class
- B9.5III
- Distance
- 143 light-years
- Highest at midnight
- late June
- Position (J2000)
- RA 18h 24m · Dec −34° 23′
A blue-white giant, around 11,000 K, like Rigel and Spica. About 77× brighter than the faintest star the eye can see. Gives off about 310 times the Sun's visible light. The light you are seeing left around 1883.
When to see it
On the night of Fri 25 Jun 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 23:08 | 01:10 · 4° | 03:13 |
| New York EDT | 21:30 | 01:05 · 15° | 04:40 |
| Singapore GMT+8 | 19:20 | 01:16 · 54° | 07:11 |
| Sydney GMT+10 | 16:19 | 00:07 · 90° | 07:55 |
Common questions
- Can I see it from 50° north?
- Only just. At its highest it is 6° above the southern horizon, so it needs a clear, flat view that way and clean air.
- Can I see it from 35° south?
- Yes, and well placed: at its highest it passes almost overhead, 89° up, above most of the air’s haze.
- When is the best time of year to see it?
- Around late June, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late September it is highest in the early evening, and in late March not until the hours before dawn.
- How far away is it, and how bright?
- It is 143 light-years away, and shines at magnitude 1.79 in our sky. From that far, the Sun would be a star of magnitude 8.0: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 1.79 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Shaula: Kaus Australis is 11° east of it, a fist at arm’s length.
Look for
From 50° north it barely clears the horizon, at 6°; from 35° north it climbs to 21°; from the equator it climbs to 56°; from 35° south it climbs to 89°.
Science
Kaus Australis’s surface is about 11,000 K, some 5,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 260 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 −1.4, about as bright as Sirius looks to us.
Did you know
Against Shaula, the brighter star the hop starts from: the two look about as bright as each other in our sky; Shaula is 571 light-years away and Kaus Australis 143 light-years, so side by side Shaula would give off 19 times as much light as Kaus Australis.
Science
Kaus Australis is the 69th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Alnasl, about 48 light-years from it; on our sky the two are 5.5° apart.
Look for
The Sun passes 11° north of Kaus Australis around late December, 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 5 hours a day, from 35° north about 8 and from 35° south about 16. It is 10° from the plane of the Milky Way, inside the band a dark sky shows.