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66 Aquilae, abbreviated 66 Aql, is a fifth-magnitude star in the constellation of Aquila. 66 Aquilae is its Flamsteed designation. It is visible to the naked eye, having an apparent visual magnitude of 5.44. The star shows an annual parallax shift of 4.4 mas, which provides a distance estimate of around 730 light years. It is moving closer to the Earth with a heliocentric radial velocity of −30 km/s. The motion of the star over time suggests some displacement, which may indicate it is a close binary system.

This is an aging giant star with a stellar classification of K5 III, which indicates it has exhausted the supply of hydrogen at its core and expanded off the main sequence. The measured angular diameter of this star, after correcting for limb darkening, is 2.44±0.03 mas. At its estimated distance, this yields a physical size of roughly 59 times the radius of the Sun. It is radiating 635 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,040 K, giving the star an orange hue. This star was part of the obsolete constellation Anguilla.

References

1. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
2. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
3. ^ Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
4. ^ Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
5. ^ Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(10^{-3}\cdot 225\cdot 2.44)\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 118\cdot R_{\bigodot }\end{aligned}}}$

6. ^ McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
7. "66 Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 1, 2018.
8. Mason, Brian D.; Martin, Christian; Hartkopf, William I.; Barry, Donald J.; Germain, Marvin E.; Douglass, Geoffrey G.; Worley, Charles E.; Wycoff, Gary L.; Ten Brummelaar, Theo; Franz, Otto G. (1999), "Speckle Interferometry of New and Problem HIPPARCOS Binaries", The Astronomical Journal, 117 (4): 1890, Bibcode:1999AJ....117.1890M, doi:10.1086/300823
9. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039

v t e Constellation of Aquila
Aquila in Chinese astronomy List of stars in Aquila
Stars	Bayer α (Altair) β (Alshain) γ (Tarazed) δ ε ζ (Okab) η θ (Tseen Foo) ι κ λ μ ν ξ (Libertas) ο π σ τ υ φ χ ψ ω ω A b c d e f g h i k l Flamsteed 4 5 7 8 10 11 18 19 20 21 22 23 24 42 45 46 51 56 57 58 62 64 66 68 69 70 14 Sge 62 Ser 64 Sgr Variable R U V W TT FF QS V368 V450 V500 V603 V604 V605 V606 V923 V1286 V1291 V1298 V1302 V1315 V1333 V1339 V1427 V1428 V1429 V1472 V1487 V1494 V1654 V1672 V1691 V1703 (Phoenicia) V1828 V1936 HR 7099 7143 7288 7300 7307 7396 7456 7569 7598 7599 7693 7717 7803 HD 179079 183263 187734 192699 (Chechia) Other CoRoT-2 CoRoT-3 CoRoT-8 Gaia BH3 HAT-P-41 PSR J1856+0245 PSR J1903+0327 PSR B1913+16 (Hulse–Taylor) PSR J1951+1123 SGR 1900+14 SS 433 W43A W49-2 WASP-80 (Petra) WD J1953−1019 ZTF J1901+1458
Exoplanets CoRoT-2b CoRoT-3b CoRoT-8b CoRoT-10b HD 179079 b HD 183263 b c HD 192263 b HD 192699 b ξ Aquilae b
Star clusters NGC 6709 NGC 6738 NGC 6755 NGC 6756 NGC 6760
Nebulae	NGC 6741 6751 6778 6781 6790 Other Abell 48 Abell 70 E Nebula Hen 2-428 HESS J1857+026 Kesteven 75 Smith's Cloud W43 W49 W49B W50
Galaxies	NGC 6814 Other IC 1327
Category

• K-type giants
• Aquila (constellation)
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects