Delta2 Telescopii
Star in the constellation Telescopium
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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]
| 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 |