Delta2 Telescopii

Delta² Telescopii is a blue-white-hued binary star^[7] system in the southern constellation of Telescopium. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.05.^[2] The distance to this system, as determined with an annual parallax shift of 2.73 mas,^[1] is roughly 1,200 light-years. At that distance, the visual magnitude of the star is diminished by an extinction of 0.36 due to interstellar dust.^[6] The pair have an orbital period of 21.7 days and an eccentricity of 0.22.^[7] For the merged stellar classification, Houk (1978) gives B3 IV/V,^[4] while Levato (1975) lists a more evolved class of B3 III.^[5] It appears to be a relatively young system, barely 40 million years old.^[8]

For other stars with this Bayer designation, see δ Telescopii.

Delta² Telescopii

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Telescopium
Right ascension	18h 32m 01.94437s[1]
Declination	−45° 45′ 26.5636″[1]
Apparent magnitude (V)	5.05[2]
Characteristics
Evolutionary stage	subgiant[3]
Spectral type	B3 IV/V[4] or B3 III[5]
U−B color index	−0.52[2]
B−V color index	−0.12[2]
Astrometry
Proper motion (μ)	RA: +0.16[1] mas/yr Dec.: −10.23[1] mas/yr
Parallax (π)	2.73±0.26 mas[1]
Distance	1,200 ± 100 ly (370 ± 30 pc)
Absolute magnitude (MV)	−1.46[6]
Orbit[7]
Period (P)	21.7056 d
Eccentricity (e)	0.22
Periastron epoch (T)	2,435,216.669 JD
Argument of periastron (ω) (secondary)	12.7°
Semi-amplitude (K1) (primary)	34.9 km/s
Details
Mass	7.6±0.1[8] M☉
Radius	7,2[3] R☉
Luminosity (bolometric)	5,129[9] L☉
Surface gravity (log g)	3.37[3] cgs
Temperature	17,100[9] K
Rotational velocity (v sin i)	0[10] or 45[5] km/s
Age	39.8±7.6[8] Myr
Other designations
δ2 Tel, CD−45°12556, HD 170523, HIP 90853, HR 6938, SAO 229095[11]
Database references
SIMBAD	data