RR Lyrae
RR Lyrae is a variable star in the Lyra constellation, figuring in its west near to Cygnus. As the brightest star in its class, it became the eponym for the RR Lyrae variable class of stars and it has been extensively studied by astronomers. RR Lyrae variables serve as important standard candles that are used to measure astronomical distances. The period of pulsation of an RR Lyrae variable depends on its mass, luminosity and temperature, while the difference between the measured luminosity and the actual luminosity allows its distance to be determined via the inverse-square law. Hence, understanding the period-luminosity relation for a local set of such stars allows the distance of more distant stars of this type to be determined.
Illustration of the typical light curve for RR Lyrae. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 25m 27.91285s |
| Declination | +42° 47′ 03.6942″ |
| Apparent magnitude (V) | 7.195 (7.06–8.12) |
| Characteristics | |
| Spectral type | A7III - F8III |
| U−B color index | +0.172 |
| B−V color index | +0.181 |
| Variable type | RR Lyr |
| Astrometry | |
| Radial velocity (Rv) | -72.4 km/s |
| Proper motion (μ) | RA: -109.68 mas/yr Dec.: -195.75 mas/yr |
| Parallax (π) | 3.64 ± 0.23 mas |
| Distance | 900 ± 60 ly (270 ± 20 pc) |
| Absolute magnitude (MV) | 0.600 ± 0.126 |
| Details | |
| Mass | 0.65 M☉ |
| Radius | 5.1 to 5.6 R☉ |
| Luminosity | 49 ± 5 L☉ |
| Surface gravity (log g) | 2.4 ± 0.2 cgs |
| Temperature | 6,125 ± 50 K |
| Metallicity [Fe/H] | –1.16 dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
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