Sagitta (The Arrow) & Messier 71 Guide
Sagitta IAU constellation (80 sq deg, rank 86): third-smallest constellation, flying inside the Summer Triangle in August with Sham and M71.
Sky Navigation & Astrophysical Context
At just 80 square degrees, Sagitta is the third-smallest constellation in the entire sky (after Crux and Equuleus), yet it is one of Ptolemy's original 48 classical constellations because its four main stars genuinely look like a feathered arrow flying eastward through the Summer Triangle, 10° north of Altair and immediately south of Vulpecula. In Greek mythology, Sagitta represents the arrow shot by Heracles at the Aquila eagle of Zeus or at the Stymphalian Birds.
Two feather stars at the western tail—Sham (Alpha Sagittae, V = +4.38, a rare G1 II bright giant situated right in the Hertzsprung Gap) and Beta Sagittae (+4.38)—join down the shaft through the M2 II-III + B9 V binary Delta Sagittae (+3.82) to the eastern arrowhead tip, the K5 III red-orange giant Gamma Sagittae (+3.51).
Midway along the Arrow's shaft between Delta and Gamma Sagittae sits Messier 71 (NGC 6838, V = +8.2): for much of the 20th century astronomers debated whether M71 was a very dense, compressed open cluster (like M11) or a loose, metal-rich disk globular cluster ([Fe/H] ≈ −0.78 at 4.0 kiloparsecs), before radial-velocity and HST photometry confirmed it as a young, metal-rich globular cluster. Sagitta is also a classic launchpad for star-hopping 3.2° north from Gamma Sagittae into Vulpecula to center the Dumbbell Nebula (Messier 27).
Equatorial Center Position & Transit Altitude
Sagitta is centered near Right Ascension 19h 39m 00s, Declination +18° 51′ 36″ (The Arrow).
Practical Star-Hopping & Observing Tips
- Look 10° due north of brilliant Altair inside the Summer Triangle to trace the unmistakable 4°-long arrow of Alpha, Beta, Delta, and Gamma Sagittae.
- Center a low-power eyepiece or 10×50 binoculars midway between Delta and Gamma Sagittae to spot the arrowhead-shaped glow of globular cluster Messier 71.
- Step 3.2° due north from the arrowhead star Gamma Sagittae (past 14 Vulpeculae) to land directly on the Dumbbell Nebula (M27) in neighboring Vulpecula.
Notable Celestial Objects in & Near Sagitta
| Object | Family | Classification | RA (J2000) | Dec (J2000) | Min. Instrument |
|---|---|---|---|---|---|
| Dumbbell Nebula (Messier 27 in Vulpecula) | nebulae | Planetary nebula (bipolar lobe system viewed equator-on) | 19h 59m 36.34s | +22° 43′ 16.1″ | 7×50 binoculars |
| 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 |
| Albireo (Beta Cygni Color Double Star) | multiple-stars | Wide visual double star (K3 II amber giant + B8 V blue-green dwarf) | 19h 30m 43.29s | +27° 57′ 34.8″ | 10×50 binoculars (best in 50–100 mm telescope at 30×–60×) |
| Messier 71 (NGC 6838 Disk Globular Cluster) | globular-clusters | Globular cluster | 19h 53m 46.49s | +18° 46′ 45.1″ | 10×50 binoculars / 80 mm telescope |
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