Atlas (star)
Template:Location mark Atlas in the Pleiades cluster (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Taurus |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | 3.63[2] (3.84 / 5.46)[3] |
| Characteristics | |
| Spectral type | B8III[4] |
| U−B Template:Engvar | −0.36[5] |
| B−V Template:Engvar | −0.08[5] |
| Variable type | SPB[6] |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[7] km/s |
| Proper motion (μ) | RA: +19.079 mas/yr[1] Dec.: −46.193 mas/yr[1] |
| Parallax (π) | 8.1184±0.4791 mas[1] |
| Distance | Template:Cvt ly (Script error: No such module "val".[8] pc) |
| Absolute magnitude (MV) | −1.82[9] |
| Orbit[8] | |
| Primary | Aa1 |
| Companion | Aa2 |
| Period (P) | Script error: No such module "val". |
| Semi-major axis (a) | Script error: No such module "val". |
| Eccentricity (e) | Script error: No such module "val". |
| Inclination (i) | Script error: No such module "val".° |
| Longitude of the node (Ω) | Script error: No such module "val".° |
| Periastron epoch (T) | BJD Script error: No such module "val". |
| Argument of periastron (ω) (secondary) | Script error: No such module "val".° |
| Semi-amplitude (K1) (primary) | Script error: No such module "val". km/s |
| Semi-amplitude (K2) (secondary) | Script error: No such module "val". km/s |
| Details[8] | |
| Aa1 | |
| Mass | Script error: No such module "val". Template:Solar mass |
| Radius | Script error: No such module "val". (equatorial) Script error: No such module "val". (polar) Template:Solar radius |
| Luminosity | 1,260 Template:Solar luminosity |
| Surface gravity (log g) | Script error: No such module "val". cgs |
| Temperature | Script error: No such module "val". K |
| Rotational velocity (v sin i) | Script error: No such module "val". km/s |
| Aa2 | |
| Mass | Script error: No such module "val". Template:Solar mass |
| Radius | Script error: No such module "val".[10] Template:Solar radius |
| Luminosity | 250 Template:Solar luminosity |
| Surface gravity (log g) | Script error: No such module "val". cgs |
| Temperature | Script error: No such module "val". K |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Rotational velocity (v sin i) | Script error: No such module "val". km/s |
| Other designations | |
| Template:Odlist | |
| Database references | |
| SIMBAD | data |
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Atlas Template:IPAc-en,[11] designation 27 Tauri, is a binary star system in the constellation of Taurus. It is a member of the Pleiades, an open star cluster (M45). It is 444 light-years (136 parsecs) away,[8] and is 3.92 degrees north of the ecliptic.
Nomenclature
27 Tauri is the star's Flamsteed designation. It has the proper name Atlas; Atlas was a Titan and the father of the Pleiades sisters in Greek mythology.
In 2016 the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalogue and standardize proper names for stars. The WGSN approved the name Atlas for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[13]
Properties
Atlas is a binary star system, orbiting in under a year. An outer star, component Ab (sometimes component B, such as in CCDM and SIMBAD[14]), has been claimed to be resolved at a distance of Script error: No such module "val". from the unresolved spectroscopic binary, with an apparent magnitude of 6.8, three magnitudes fainter than the combined magnitude of the closer pair. It would have an estimated mass of twice that of the Sun. However, no new detections have been reported since 1929, even though more recent instruments would be able to identify it.[8] In the WDS catalog, there are 8 other stars, ranging from B-I, which have been classed as companions of Atlas.[15]
The pair have a well-defined orbit with a period of 291 days, a semi-major axis of Script error: No such module "val"., and an eccentricity of 0.24. At an inclination of 108° to the plane of the sky, it does not show eclipses.[16] Although the two stars cannot be resolved, the primary, component Aa1, is calculated to be 1.6 magnitudes brighter than the secondary, component Aa2.[15] The primary star is rapidly rotating and is significantly oblate; the ratio of the polar to equatorial radius is 0.83. It rotates at an inclination of either Script error: No such module "val". or Script error: No such module "val"., the latter consistent with its rotation being aligned with the orbit.[8]
Low amplitude variability of the brightness of Atlas was tentatively detected in observations by STEREO and clearly detected by Kepler/K2. The light curve varies with several periods, the most prominent being 2.427, 0.7457 and 1.214 days.[10]
References
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