Epoch J2000 Equinox J2000
|Right ascension||18h 26m 58.41604s|
|Declination||–45° 58′ 06.4498″|
|Apparent magnitude (V)||3.51|
|Spectral type||B3 IV|
|U−B color index||−0.64|
|B−V color index||−0.17|
|Radial velocity (Rv)||−0.2 km/s|
|Proper motion (μ)||RA: −16.95 mas/yr
Dec.: −53.09 mas/yr
|Parallax (π)||11.74 ± 0.17 mas|
|Distance||278 ± 4 ly
(85 ± 1 pc)
|Mass||5.2 ± 0.4 M☉|
|Radius||3.3 ± 0.5 R☉|
|Surface gravity (log g)||4.12 ± 0.20 cgs|
|Temperature||16,700 ± 800 K|
|Rotational velocity (v sin i)||14 ± 8 km/s|
|Age||24.1 ± 7.5 Myr|
Alpha Telescopii (α Tel, α Telescopii) is the brightest star in the constellation Telescopium, with an apparent visual magnitude of 3.5. 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. Parallax measurements put it at a distance of 278 light-years (85 parsecs) from Earth.
This star is much larger than the Sun, with about five times the mass and three times the radius. The spectrum of the star matches a stellar classification of B3 IV, 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, giving it the characteristic blue-white hue of a B-type star.
This is a type of variable star known as a slowly pulsating B star. It has a longitudinal magnetic field with a mean strength of –233 ± 43 G. A projected stellar rotation velocity of about 14 km s−1 is considered low for a star of this type, which may indicate it is being viewed from nearly pole-on.
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