Kaus Australis (Epsilon Sagittarii)
Kaus Australis (Epsilon Sagittarii) is a star in the constellation Sagittarius, magnitude 1.8.
The brightest star of the Teapot — spinning closer to break-up than any other star measured in our galaxy.
Kaus Australis spins at 95% of the speed that would tear it apart — the highest rate ever measured for a star in the Milky Way. The spin squashes it so that it is about a third bigger around the equator than over the poles. The poles, at about 11,700 K, are far hotter than the equator, at about 7,400 K, and a disc of gas spun off its middle surrounds it.
Such a spin is hard to explain for a lone star. More likely it was spun up long ago when gas poured onto it from a partner. Today it is a star of about 3.8 solar masses, shining 500 times as brightly as the Sun, with a smaller, Sun-like companion first seen in 1993.
Its name mixes Arabic qaws, ‘bow’, with Latin australis, ‘southern’ — the southern part of the Archer’s bow.
Kaus Australis (Epsilon Sagittarii) is 140 light-years away: the light we see from it set off around 1885, 7 years after Edison lit his first practical light bulb — the start of light pollution.
Did you know?
- The Bark. The Babylonian star compendium MUL.APIN lists Kaus Australis as MA.GUR8, ‘the Bark’ — an old word for a boat.
- Taugi’s fishing basket. The Kalapalo people of Mato Grosso in Brazil link it with stars in the Scorpion’s tail as Taugi kusugu, ‘Taugi’s fishing basket’.
- The Winnowing Basket. In China it is the third star of Jī, the Winnowing Basket, a pattern made with three other stars of Sagittarius.
The brightest star of Sagittarius, a blue-white star at the base of the Teapot’s spout. Sweep binoculars from the spout upwards: the Milky Way’s star clouds rise from it like steam.
When and where to see it
It is best placed in the evening sky around July, when it crosses the meridian at about 10 pm local time (around midnight in June). It can be seen from everywhere south of 56°N and never sets south of 56°S.
At its highest it stands 6° up from 50°N, 21° up from 35°N, 56° up from the equator, 89° up from 35°S.
Facts
- Type
- Star
- Constellation
- Sagittarius
- Designations
- Epsilon Sagittarii, ε Sgr, 20 Sgr, HR 6879, HD 169022, HIP 90185
- Magnitude
- 1.8
- Position
- RA 18h 24.2m, Dec −34° 23′ (J2000)
- Spectral type
- B9IVp_lB?
- Colour
- white (B−V 0.01)
- Distance
- 140 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Kaus Australis (Epsilon Sagittarii) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.