Aquila (The Eagle) Constellation & Altair
Aquila IAU constellation (652 sq deg, rank 22): August Milky Way landmark anchored by Altair (+0.76), Tarazed, and dark Barnard nebulae along the Rift.
Sky Navigation & Astrophysical Context
Straddling the celestial equator across 652 square degrees, Aquila flies northward through the Great Rift of the summer Milky Way directly south of Cygnus and Sagitta. Its unmistakable head is marked by the first-magnitude A7 V star Altair (Alpha Aquilae, V = +0.76), which forms the southern vertex of the Summer Triangle and rotates so rapidly (equatorial velocity ~240 km/s) that its polar diameter is flattened by roughly 20 percent.
Altair is closely flanked by two third- and fourth-magnitude wing-shoulder stars—the orange K3 II bright giant Tarazed (Gamma Aquilae, +2.72) to the northwest and the G8 IV subgiant Alshain (Beta Aquilae, +3.71) to the southeast—forming the classic 'Family of Aquila' pointer triad. Stretching southwestward across the Milky Way's central lane, Delta, Lambda, and Zeta Aquilae outline the Eagle's outstretched wings and tail.
Because the Aquila Rift of molecular clouds bisects the constellation, wide-field observers encounter dramatic dark nebulae—most notably Barnard 142 and Barnard 143 ('Barnard's E' dark nebula) just west of Tarazed—alongside classic Cepheid prototype Eta Aquilae (+3.5 to +4.4 over 7.1766 days), open cluster NGC 6709, and planetary nebulae NGC 6751 and NGC 6781.
Equatorial Center Position & Transit Altitude
Aquila is centered near Right Ascension 19h 40m 12s, Declination +03° 24′ 36″ (The Eagle).
Practical Star-Hopping & Observing Tips
- Locate Altair via its two flanking companion stars, orange Tarazed (+2.72) 2° northwest and Alshain (+3.71) 2.5° southeast.
- Scan 1.5° west of Tarazed with 10×50 binoculars under dark skies to see the crisp C- or E-shaped silhouette of the Barnard 142/143 dark cloud against the Milky Way.
- Track the naked-eye brightness changes of the classical Cepheid Eta Aquilae over its 7.18-day pulsation period using Delta (+3.36) and Iota Aquilae (+4.36) as comparison stars.
Notable Celestial Objects in & Near Aquila
| Object | Family | Classification | RA (J2000) | Dec (J2000) | Min. Instrument |
|---|---|---|---|---|---|
| Altair (Alpha Aquilae Rapid Rotator) | stars | Rapidly rotating A-type main-sequence star (Delta Scuti variable) | 19h 50m 47.00s | +08° 52′ 06.0″ | Naked eye |
| Vega (Alpha Lyrae Zero-Point Star) | stars | Rapidly rotating A-type main-sequence star with debris disk | 18h 36m 56.34s | +38° 47′ 01.3″ | Naked eye |
| 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 |
| W49B Supernova Remnant (Jet-Driven Barrel SNR) | supernova-remnants | Young bipolar jet-driven core-collapse supernova remnant | 19h 11m 11.00s | +09° 06′ 00.0″ | Near-IR / Radio / X-ray observatory archive (visual Milky Way Rift landmark) |
| SS 433 (V1343 Aquilae) — Galactic Microquasar | compact-objects | Galactic Microquasar / X-Ray Binary | 19h 11m 49.56s | +04° 58′ 57.8″ | 250–400 mm telescope visually; 150 mm+ CCD astrograph |
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