Kappa Arae
A G-type giant star in the southern constellation Ara.
Kappa Arae is a solitary giant star located in the southern constellation Ara. Its Bayer designation, Latinized from κ Arae, is often shortened to Kappa Ara or κ Ara. The star has an apparent visual magnitude of 5.20, making it just barely visible without a telescope. Parallax measurements place it roughly 430 light-years (130 parsecs) from Earth, with an uncertainty of about 4 light-years. It is moving away from our solar system at a radial velocity of +17.8 km/s.
Classified as a G8 III giant, Kappa Arae has exhausted the hydrogen fuel in its core and evolved off the main sequence. It has about 3.2 times the Sun’s mass, but its outer envelope has swelled to roughly 18 times the Sun’s radius. The star shines with 166 times the Sun’s luminosity, and its photosphere has an effective temperature of 4,855 K—hot enough to give it the golden hue typical of G-type stars. It emits coronal X-rays and has been tentatively identified as a mild barium star, though this classification remains uncertain.
Kappa Arae has two optical companions, both of 14th magnitude, located at angular distances of 25 and 30 arcseconds.
- Constellation
- Ara
- Apparent magnitude
- 5.20
- Distance
- approximately 430 light-years (130 parsecs)
- Spectral type
- G8 III
- Mass
- 3.2 times the Sun's mass
- Radius
- about 18 times the Sun's radius
- Luminosity
- 166 times the Sun's luminosity
Lore & Background
Kappa Arae is a giant star with a stellar classification of G8 III, having exhausted the hydrogen at its core and evolved away from the main sequence. With 3.2 times the mass of the Sun, its outer envelope has expanded to about 18 times the Sun's radius. It is radiating 166 times the luminosity of the Sun from its photosphere at an effective temperature of 4,855 K. This is hot enough for it to shine with the golden-hued glow of a G-type star.
Reader's Guide
Kappa Arae is a notable example of a G-type giant star, representing a late stage of stellar evolution after core hydrogen exhaustion. Its distance of about 430 light-years places it within the range of naked-eye visibility for observers in the southern hemisphere. The star is a source for coronal X-ray emission and has been reported as a mild barium star, although the latter is questionable. It has two 14th magnitude optical companions at angular distances of 25 and 30 arcseconds, which are not physically associated. The star's radial velocity of +17.8 km/s indicates it is receding from the Sun. Its study contributes to understanding the properties of evolved stars and their chemical peculiarities.
Did You Know?
- Kappa Arae has an apparent visual magnitude of 5.20, making it faintly visible to the naked eye.
- The star is receding from the Sun with a radial velocity of +17.8 km/s.
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