Ara (The Altar) Constellation Sky Guide
Ara IAU constellation (237 sq deg, rank 63): July southern Milky Way field south of Scorpius, led by Beta Arae (+2.84), NGC 6397, and Westerlund 1.
Sky Navigation & Astrophysical Context
Tucked immediately south of the curved stinger of Scorpius, Ara spans 237 square degrees of the rich southern Milky Way and represents the mythological incense altar upon which the Olympian gods swore allegiance before battling the Titans. In classical lore, the bright clouds of the southern Milky Way rising through Ara were envisioned as aromatic smoke ascending from the burning censer.
The constellation's two brightest stars—the K3 Ib-II orange supergiant Beta Arae (+2.84) and the rapidly rotating B2 Vnn emission-line star Alpha Arae (+2.93)—lie within a degree of one another, while Gamma Arae (+3.34), Zeta Arae (+3.13), and Eta Arae (+3.76) complete the double-column outline of the Altar.
Ara is home to some of the Milky Way's most extraordinary stellar populations: NGC 6397 (Caldwell 86) at 2.39 kiloparsecs is one of the two closest globular clusters to the Sun and a textbook core-collapse globular; Westerlund 1 is the most massive young super star cluster known in our galaxy, housing dozens of Wolf-Rayet stars, yellow hypergiants, and red supergiants; and Mu Arae (Cervantes) hosts a well-studied four-planet system.
Equatorial Center Position & Transit Altitude
Ara is centered near Right Ascension 17h 23m 24s, Declination −53° 34′ 48″ (The Altar).
Practical Star-Hopping & Observing Tips
- Drop 8° south from Theta Scorpii (Sargas) in the Scorpion's tail to locate the paired stars Alpha and Beta Arae.
- Center NGC 6397 in binoculars or a small telescope 2.5° northeast of Beta Arae; at 100× its compressed core resolves into chains of 10th-magnitude red giants.
- Compare the warm orange hue of supergiant Beta Arae with the blue-white B1 Ib supergiant Gamma Arae just 50 arcminutes to its south.
Notable Celestial Objects in & Near Ara
| Object | Family | Classification | RA (J2000) | Dec (J2000) | Min. Instrument |
|---|---|---|---|---|---|
| Omega Centauri (NGC 5139 Cluster) | globular-clusters | Globular cluster / stripped dwarf galaxy nucleus | 13h 26m 47.24s | -47° 28′ 46.1″ | Naked eye (south of 35°N) |
| Lagoon Nebula (Messier 8 / NGC 6523) | nebulae | Giant H II emission nebula with embedded open cluster NGC 6530 | 18h 03m 47.00s | -24° 23′ 12.0″ | Naked eye / 7×50 binoculars |
Scientific Sources Cited
- IAU Official Constellation Boundaries & Designations (IAU 88 Recognized Constellations): Delporte, E. 1930, Délimitation scientifique des constellations (IAU / Cambridge University Press) — International Astronomical Union (IAU)
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg