Article · Wikipedia archive · Last revised Jul 11, 2026

Alpha Scuti

Alpha Scuti, also named Tianbian, is an orange-hued star in the southern constellation of Scutum. It is faintly visible to the naked eye with an apparent visual magnitude of 3.83. Based upon an annual parallax shift of 16.38 mas as seen from the Earth, 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.

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α Scuti
Location of α Scuti (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Scutum1
Right ascension 18h 35m 12.42776s2
Declination −08° 14′ 38.6529″2
Apparent magnitude (V) 3.833
Characteristics
Spectral type K3III4
U−B color index +1.533
B−V color index +1.343
Astrometry
Radial velocity (Rv)+36.505 km/s
Proper motion (μ) RA: −17.002 mas/yr
Dec.: −313.522 mas/yr
Parallax (π)16.38±0.22 mas2
Distance199 ± 3 ly
(61.1 ± 0.8 pc)
Absolute magnitude (MV)−0.081
Details
Mass1.336 M☉
Radius206 R☉
Luminosity1861 L☉
Surface gravity (log g)1.966 cgs
Temperature4,3157 K
Metallicity [Fe/H]−0.041 dex
Rotational velocity (v sin i)1.78 km/s
Other designations
Tianbian, α Sct, 1 Aql, NSV 11056, BD−08°4638, FK5 1482, GC 25385, HD 171443, HIP 91117, HR 6973, SAO 142408, LTT 7377
Database references
SIMBADdata

Alpha Scuti, also named Tianbian,9 is an orange-hued star in the southern constellation of Scutum. It is faintly visible to the naked eye with an apparent visual magnitude of 3.83.3 Based upon an annual parallax shift of 16.38 mas as seen from the Earth,2 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.5

Nomenclature

Alpha Scuti, Latinized from α Scuti and abbreviated α Sct, is the star's Bayer designation. It has the Flamsteed designation 1 Aquilae, since Flamsteed did not recognize Scutum as a separate constellation and treated it as part of Aquila.10

In Chinese astronomy, this star is part of the asterism Tiān Biàn (天弁), which represents a market officer and literally means "Celestial Cap" in reference to ceremonial headgear. The IAU Working Group on Star Names adopted the name Tianbian for this star on 18 June 2026, after this Chinese constellation.9

Properties

With a stellar classification of K3 III,4 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 3.87.11 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 1861 times the Sun's luminosity from its inflated photosphere at an effective temperature of 4,315 K.7

References

References

  1. 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. XHIP record for this object at VizieR.
  2. 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
  3. 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.
  4. 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.
  5. 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.
  6. 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. 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. "IAU Catalog of Star Names". Retrieved 21 June 2026.
  10. 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.
  11. 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....102025S.
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