R Lyrae
Star in the constellation Lyra
From Wikipedia, the free encyclopedia
R Lyrae, also known as its Flamsteed designation 13 Lyrae, is a 4th magnitude semiregular variable star in the constellation Lyra, approximately 350 light years away from Earth. It is visible to the naked eye. It is a red giant star of the spectral type M5III, currently at the last stages of evolution. It is much larger and brighter, yet cooler, than the Sun. In the near-infrared J band, it is brighter than the nearby Vega.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 18h 55m 20.101223s[1] |
| Declination | +43° 56′ 45.9215″[1] |
| Apparent magnitude (V) | 3.9 - 5.0[2] |
| Characteristics | |
| Spectral type | M5 III[3] |
| Apparent magnitude (J) | −0.90[4] |
| U−B color index | +1.41[4] |
| B−V color index | +1.59[4] |
| Variable type | SRb[2] |
| Astrometry | |
| Radial velocity (Rv) | −27.15[5] km/s |
| Proper motion (μ) | RA: 21.05[1] mas/yr Dec.: 82.06[1] mas/yr |
| Parallax (π) | 10.94±0.12 mas[1] |
| Distance | 298 ± 3 ly (91 ± 1 pc) |
| Absolute magnitude (MV) | −1.1[3] |
| Details | |
| Mass | 1.8±0.2[6] M☉ |
| Radius | 195[6][a] R☉ |
| Luminosity | 4,130[6][b] L☉ |
| Surface gravity (log g) | 0.47[7] cgs |
| Temperature | 3,313[6] K |
| Other designations | |
| R Lyrae, 13 Lyrae, HR 7157, BD+43°3117, HD 175865, SAO 47919, HIP 92862, GC 25996, GSC 03131-02155 | |
| Database references | |
| SIMBAD | data |
R Lyrae is unusual in that it is a red star with a high proper motion, greater than 50 milliarcseconds a year.[8] It is one of the brightest stars at the K band, having an apparent magnitude of −2.08, only 14 stars are brighter.[9]
In 1856, Joseph Baxendell announced that the star, then called 13 Lyrae, is a variable star.[11] In 1907 it appeared with its variable star designation, R Lyrae, in Annie Jump Cannon's Second Catalog of Variable Stars.[12] The variability is not consistent and regular, but periods of 46, 64, 378, and 1,000 days have been reported, with the 46-day period being the strongest.[3][13]
It is calculated that R Lyrae was a 2.0 M☉ star on the main sequence, similar to Sirius A today. It is now an oxygen-rich asymptotic giant branch star, with both hydrogen and helium shells fusing. Due to stellar mass loss, R Lyrae now has a mass of 1.8 M☉.[6]
Notes
- Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
- .
- Calculated using the absolute bolometric magnitude of R lyrae, with respect to the Sun's absolute bolometric magnitude of 4.83:
100.4(4.74+(−4.3) = 4130.48.
