Alpha Scuti

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α Scuti
Scutum constellation map.png
Location of α Scuti
Observation data
Epoch J2000      Equinox J2000
Constellation Scutum
Right ascension 18h 35m 12.42776s[1]
Declination −8° 14′ 38.6529″[1]
Apparent magnitude (V) 3.83[2]
Spectral type K3III[3]
U−B color index +1.53[2]
B−V color index +1.34[2]
Radial velocity (Rv)+36.50[4] km/s
Proper motion (μ) RA: −17.00[1] mas/yr
Dec.: −313.52[1] mas/yr
Parallax (π)16.38 ± 0.22 mas[1]
Distance199 ± 3 ly
(61.1 ± 0.8 pc)
Absolute magnitude (MV)−0.08[5]
Mass1.33[6] M
Radius20[6] R
Luminosity186[5] L
Surface gravity (log g)1.96[6] cgs
Temperature4,315[7] K
Metallicity [Fe/H]−0.04[5] dex
Rotational velocity (v sin i)1.7[8] km/s
Other designations
α Sct, BD-08°4638, FK5 1482, GC 25385, HD 171443, HIP 91117, HR 6973, LTT 7377, NSV 11056, SAO 142408
Database references

Alpha Scuti, Latinized from α Scuti, is an orange-hued star in the southern constellation of Scutum. Originally part of the Aquila constellation, alpha Scuti was a latter designation of 1 Aquilae.[9] It is faintly visible to the naked eye with an apparent visual magnitude of 3.83.[2] Based upon an annual parallax shift of 16.38 mas as seen from the Earth,[1] it is located around 199 light years from the Sun. It is moving away from the Sun with a radial velocity of +36.5 km/s.[4]


With a stellar classification of K3 III,[3] the spectrum indicates it is an evolved giant star of type K. Alpha Scuti is a suspected variable star with magnitude range reported as 3.81 to 3.87.[10] The star has an estimated 1.33 times the mass of the Sun, but the outer envelope has expanded to 20 times the Sun's radius.[6] It is radiating 186[5] times the Sun's luminosity from its inflated photosphere at an effective temperature of 4,315 K.[7]


  1. ^ a b c d e f Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
  2. ^ a b c d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  3. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. ^ a b Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (2008). "Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
  5. ^ a b c d 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. Vizier catalog entry
  6. ^ a b c d Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
  7. ^ a b Martínez, M. Isabel Pérez; Schröder, K.-P.; Cuntz, M. (2011). "The basal chromospheric Mg ii h+k flux of evolved stars: Probing the energy dissipation of giant chromospheres". Monthly Notices of the Royal Astronomical Society. 414 (1): 418–427. arXiv:1102.4832. Bibcode:2011MNRAS.414..418P. doi:10.1111/j.1365-2966.2011.18421.x. S2CID 59268230. Vizier catalog entry
  8. ^ De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (2014). "A catalog of rotational and radial velocities for evolved stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. S2CID 54046583. Vizier catalog entry
  9. ^ Wagman, M. (August 1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy. 18 (3): 212. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305. S2CID 118445625.
  10. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S.

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