What kind of star is Kaus Australis?
Kaus Australis, catalogued as Epsilon Sagittarii (ε Sgr), appears in the official constellation Sagittarius. Its apparent visual magnitude is 1.81, while its estimated distance is about 143 light-years. Astronomers classify the object as B9 IVp; suspected binary. These labels describe temperature, luminosity class or system components; they should not be read as a claim that every naked-eye point is a single isolated star.
SIMBAD classifies Epsilon Sagittarii as a chemically peculiar late-B subgiant. Its parallax places it near 143 light-years, well in front of the Sagittarius arm's rich nebulae and star fields. Spectroscopy has produced evidence for a companion, while historical visual catalogues also record a much wider faint neighbour; those are different scales of multiplicity and should not be confused. The star has exhausted or is nearing the end of core hydrogen burning, so its subgiant classification marks a transition away from the main sequence. Its apparent brightness comes from a combination of high surface temperature, greater intrinsic luminosity than the Sun and modest distance—not from membership in the distant Galactic-centre clouds that surround it in photographs.
The coordinate pair RA 18h 24m 10.32s, Dec −34° 23′ 04.6″ fixes the object's direction on the celestial sphere for the J2000 reference epoch. Right ascension works like celestial longitude measured in hours, while declination works like latitude north or south of the celestial equator. Proper motion and improved measurements can refine catalogue positions, but these coordinates are sufficiently precise for a finder chart or planetarium search.
Kaus Australis data at a glance
| Proper name | Kaus Australis | Catalogue designation | Epsilon Sagittarii (ε Sgr) |
|---|---|---|---|
| Constellation | Sagittarius | Apparent magnitude | 1.81 |
| Spectral or system type | B9 IVp; suspected binary | Estimated distance | about 143 light-years |
| Right ascension (J2000) | 18h 24m 10.32s | Declination (J2000) | −34° 23′ 04.6″ |
Values are rounded for an observer-friendly overview. Consult the linked SIMBAD record for component-level identifiers, bibliography, measurement provenance and newer catalogue values.
The name Kaus Australis
The hybrid name joins Arabic qaws, “bow,” with Latin australis, “southern.” It distinguishes this southern bow star from Kaus Media and Kaus Borealis.
Sagittarius's bow was already part of the classical archer figure, but the three Kaus names preserve Arabic descriptive astronomy. Modern Bayer notation labels the star Epsilon Sagittarii even though it is the constellation's brightest point. The IAU Working Group on Star Names standardized Kaus Australis for this particular star, removing ambiguity among historical spellings. Its mixed Arabic–Latin construction also records how European atlas makers distinguished three stars along the same inherited bow.
Modern professional catalogues retain identifiers such as the Bayer designation alongside a proper name. The International Astronomical Union standardizes which name belongs to which component—an important distinction for systems whose combined light looks like one star from Earth.
How to find Kaus Australis
Find the Teapot low in the south from northern latitudes. Kaus Australis is the bright point at the bottom of its handle-side bow, below Kaus Media. Binoculars place it against a densely populated Milky Way field, especially from a dark southern horizon.
Best on northern summer and southern winter evenings; it remains low from far-northern Europe. Visibility on a particular night still depends on latitude, season, time, horizon obstructions, weather and local light pollution. Use the interactive atlas below to check the surrounding field before observing.
Observation checklist
- Best viewed around June through August in the evening.
- Choose an unobstructed southern horizon from northern Europe.
- Use the three Kaus stars to trace Sagittarius's bow.
- A wide binocular field separates the foreground star from the background Milky Way glow.
Interesting facts about Kaus Australis
- It is the brightest star in Sagittarius despite its Epsilon designation.
- Its parallax corresponds to roughly 143 light-years.
- The spectrum is chemically peculiar rather than a textbook late-B spectrum.
- It forms the southern member of the three-star Kaus sequence.
- The Lagoon and Trifid nebula region lies nearby on the sky but far beyond the star.
Continue from Kaus Australis into the night sky
Use the Sagittarius constellation guide to place this star within its larger pattern. When you are ready to observe, compare dark-sky places, find a nearby observatory, or follow our practical guide to finding a star in the night sky. Symbolically registered names are kept separately in the searchable Star-Register catalogue.
Sources and further reading
Measurements are rounded for readability. Multiple systems, variable stars and distant supergiants can have component-specific or model-dependent values. Survey panels show photographic sky fields, not the physical surface of the star.