Lambda1 Tucanae
Binary star system in the constellation Tucana
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Lambda1 Tucanae is the Bayer designation for one member of a pair of stars sharing a common proper motion through space,[8] which lie within the southern constellation of Tucana. As of 2013, the pair had an angular separation of 20.0 arc seconds along a position angle of 82°.[2] Together, they are barely visible to the naked eye with a combined apparent visual magnitude of 6.21.[5] Based upon an annual parallax shift for both stars of approximately 16.5[1][3] mas as seen from Earth, this system is located roughly 198 light years from the Sun.
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Tucana |
| A | |
| Right ascension | 00h 52m 24.5198s[1] |
| Declination | −69° 30′ 13.544″[1] |
| Apparent magnitude (V) | 6.70[2] |
| B | |
| Right ascension | 00h 52m 28.3487s[3] |
| Declination | −69° 30′ 10.382″[3] |
| Apparent magnitude (V) | 7.35[2] |
| Characteristics | |
| A | |
| Spectral type | F7 IV-V[4] |
| U−B color index | +0.07[5] |
| B−V color index | +0.55[5] |
| B | |
| Spectral type | G0/2V[4] |
| Astrometry | |
| A | |
| Radial velocity (Rv) | +29.4±0.2[6] km/s |
| Proper motion (μ) | RA: 3.849±0.050[1] mas/yr Dec.: −67.462±0.040[1] mas/yr |
| Parallax (π) | 16.4907±0.0293 mas[1] |
| Distance | 197.8 ± 0.4 ly (60.6 ± 0.1 pc) |
| Absolute magnitude (MV) | +2.68[7] |
| B | |
| Proper motion (μ) | RA: 9.966±0.062[3] mas/yr Dec.: −79.096±0.052[3] mas/yr |
| Parallax (π) | 16.5242±0.0361 mas[3] |
| Distance | 197.4 ± 0.4 ly (60.5 ± 0.1 pc) |
| Details | |
| A | |
| Mass | 1.55[8] M☉ |
| Luminosity | 7[9] L☉ |
| Surface gravity (log g) | 3.90[10] cgs |
| Temperature | 6,325[10] K |
| Metallicity [Fe/H] | +0.09[10] dex |
| Age | 2.6[10] Gyr |
| B | |
| Mass | 1.38[8] M☉ |
| Radius | 1.86[3] R☉ |
| Luminosity | 3.534[3] L☉ |
| Surface gravity (log g) | 3.94[11] cgs |
| Temperature | 5,797[3] K |
| Metallicity [Fe/H] | +0.04[11] dex |
| Rotational velocity (v sin i) | 3.6[12] km/s |
| Other designations | |
| DUN 2, CCDM J00524-6930AB, WDS J00524-6930AB[13] | |
| A: λ1 Tucanae, CPD−70 37, HD 5190, HIP 4084, HR 252, SAO 248269[13] | |
| B: CPD−70 38, HD 5208, HIP 4088, SAO 248271[13] | |
| Database references | |
| SIMBAD | data |
| companion | |
The brighter member, component A, is a magnitude 6.70[2] F-type star with a stellar classification of F7 IV-V.[4] The luminosity class may indicate that, at the age of 2.6 billion years,[10] it is beginning to evolve away from the main sequence. It has an estimated 1.55[8] times the mass of the Sun and is radiating 7[9] times the solar luminosity from its photosphere at an effective temperature of 6,325 K.[10] The magnitude 7.35[2] companion, component B, has 1.38[8] times the mass of the Sun. If the pair are gravitationally bound, then their estimated orbital period is 27,000 years.[8]