Star Stars · In Sagittarius
Kaus Borealis
Kaus Borealis, λ Sagittarii, is an orange giant in Sagittarius: the 138th brightest star in the night sky.
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- Constellation
- Sagittarius
- Designation
- λ Sagittarii
- Apparent magnitude
- 2.82 · 138th brightest star in the night sky
- Spectral class
- K1IIIb
- Distance
- 78.2 light-years
- Highest at midnight
- late June
- Position (J2000)
- RA 18h 28m · Dec −25° 25′
An orange giant, around 5,100 K, like Arcturus and Aldebaran. About 30× brighter than the faintest star the eye can see. Gives off about 36 times the Sun's visible light. The light you are seeing left in 1948.
When to see it
On the night of Sat 26 Jun 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 21:37 | 01:10 · 13° | 04:43 |
| New York EDT | 20:42 | 01:05 · 24° | 05:28 |
| Singapore GMT+8 | 19:19 | 01:15 · 63° | 07:12 |
| Sydney GMT+10 | 16:53 | 00:06 · 82° | 07:20 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 15° up in the south.
- Can I see it from 35° south?
- Yes, and well placed: at its highest it passes almost overhead, 80° 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 78.2 light-years away, and shines at magnitude 2.82 in our sky. From that far, the Sun would be a star of magnitude 6.7: 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 2.82 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Kaus Media: Kaus Borealis is 4.7° north of it, three fingers at arm’s length.
Look for
From 50° north it climbs to 15°; from 35° north it climbs to 30°; from the equator it climbs to 65°; from 35° south it climbs to 80°.
Science
Kaus Borealis’s surface is about 5,100 K, some 700 K cooler than the Sun’s 5,772 K, so its light is strongest at about 570 nm, 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 0.9, about as bright as Aldebaran looks to us.
Did you know
Against Kaus Media, the brighter star the hop starts from: the two look about as bright as each other in our sky; Kaus Media is 348 light-years away and Kaus Borealis 78 light-years, so side by side Kaus Media would give off 22 times as much light as Kaus Borealis.
Science
Kaus Borealis is the 32nd nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Ascella, about 16 light-years from it; on our sky the two are 8.9° apart.
Look for
Kaus Borealis lies 2.1° 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 late December, and for weeks either side it is lost in the glare. From 50° north it is above the horizon for about 7 hours a day, from 35° north about 9 and from 35° south about 15. It is 7° from the plane of the Milky Way, inside the band a dark sky shows.