Star in the constellation Ara
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! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000      Equinox J2000
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | U−B 
! style="text-align:left" | B−V 
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Eta Arae, Latinized from η Arae, is the Bayer designation for a single
 star in the southern constellation of Ara. It is approximately from Earth and is visible to the naked eye with an apparent visual magnitude of 3.76. The star is moving away from the Sun with a radial velocity of +9 km/s.
The spectrum of this star matches a stellar classification of K5 III, indicating that, at an estimated age of five billion years, it has reached the giant star stage of its evolution. With 1.12 times the mass of the Sun, it has an outer envelope that has expanded to 40 times the Sun's radius. The star is now spinning so slowly that it takes more than eleven years to complete a single rotation. Eta Arae is radiating energy into space from its photosphere with 575 times the Sun's luminosity at an effective temperature of 4,147 K, giving it the orange-hued glow of a K-type star.
It has a magnitude 13.5 optical companion, located 23.4 arcseconds away along a position angle of 118°, as of 2000.
References.
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