Alpha Telescopii

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Alpha Telescopii
Diagram showing star positions and boundaries of the Telescopium constellation and its surroundings
Cercle rouge 100%.svg

Location of α Telescopii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Telescopium
Right ascension 18h 26m 58.41604s[1]
Declination –45° 58′ 06.4498″[1]
Apparent magnitude (V) 3.51[2]
Spectral type B3 IV[3]
U−B color index −0.64[2]
B−V color index −0.17[2]
Variable type SPB[4]
Radial velocity (Rv) −0.2[5] km/s
Proper motion (μ) RA: −16.95[1] mas/yr
Dec.: −53.09[1] mas/yr
Parallax (π) 11.74 ± 0.17[1] mas
Distance 278 ± 4 ly
(85 ± 1 pc)
Mass 5.2 ± 0.4[4] M
Radius 3.3 ± 0.5[4] R
Luminosity 794[4] L
Surface gravity (log g) 4.12 ± 0.20[4] cgs
Temperature 16,700 ± 800[4] K
Rotational velocity (v sin i) 14 ± 8[4] km/s
Age 24.1 ± 7.5[6] Myr
Other designations
α Tel, CD−46° 12379, FK5 691, HD 169467, HIP 90422, HR 6897, SAO 229023.[7]
Database references

Alpha Telescopii (α Tel, α Telescopii) is the brightest star in the constellation Telescopium, with an apparent visual magnitude of 3.5.[2] Ptolemy included it in constellation Corona Australis, but it was moved to Telescopium when that constellation was created by Nicolas Louis de Lacaille in the 18th century.[8] Parallax measurements put it at a distance of 278 light-years (85 parsecs) from Earth.

This star is much larger than the Sun, with an estimated 5.2±0.4 times the mass and 3.3±0.5 times the radius.[4] The spectrum of the star matches a stellar classification of B3 IV,[3] where the luminosity class of 'IV' indicates this is a subgiant star that has nearly exhausted the supply of hydrogen at its core and is evolving away from the main sequence. Alpha Telescopii is a bright star that is radiating nearly 800 times the Sun's luminosity. This energy is being emitted from the star's outer envelope at an effective temperature of around 16,700 K,[4] giving it the characteristic blue-white hue of a B-type star.[9]

This is possibly a type of variable star known as a slowly pulsating B-type star. It has a longitudinal magnetic field with a mean strength of –233 ± 43 G.[4] A projected stellar rotation velocity of about 14 km s−1 is considered low for a star of this type,[4] which may indicate it is being viewed from nearly pole-on.[10]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357 
  2. ^ a b c d Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99). Bibcode:1966CoLPL...4...99J. 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, 
  4. ^ a b c d e f g h i j k Hubrig, S.; et al. (April 2009), "New magnetic field measurements of β Cephei stars and slowly pulsating B stars", Astronomische Nachrichten, 330 (4): 317, Bibcode:2009AN....330..317H, arXiv:0902.1314Freely accessible, doi:10.1002/asna.200811187 
  5. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E 
  6. ^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, Bibcode:2011MNRAS.410..190T, arXiv:1007.4883Freely accessible, doi:10.1111/j.1365-2966.2010.17434.x 
  7. ^ "alf Tel -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-15 
  8. ^ Ridpath, Ian, "Corona Austalis, the Southern Crown", Ian Ridpath's Star Tales, retrieved 2012-01-15 
  9. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16 
  10. ^ Kaler, James B., "ALPHA TEL (Alpha Telescopii)", Stars, University of Illinois, retrieved 2012-01-15