47 Capricorni
Star in the constellation Capricornus
From Wikipedia, the free encyclopedia
47 Capricorni is a variable star located around 940 light years from the Sun[2] in the southern constellation Capricornus,[11] near the northern border with Aquarius. It has the variable star designation of AG Capricorni and a Bayer designation of c2 Capricorni;[12] 47 Capricorni is the Flamsteed designation. This object is visible to the naked eye as a dim, red-hued point of light with an apparent visual magnitude that varies between 5.90 and 6.14. The star is receding from the Earth with a heliocentric radial velocity of +20 km/s.[7]
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 46m 16.26931s[2] |
| Declination | −09° 16′ 33.3668″[2] |
| Apparent magnitude (V) | 5.90 - 6.14[3] |
| Characteristics | |
| Evolutionary stage | AGB[4] |
| Spectral type | M2III[5] |
| B−V color index | 1.629±0.010[6] |
| Variable type | SRb[3] |
| Astrometry | |
| Radial velocity (Rv) | +19.80±0.89[7] km/s |
| Proper motion (μ) | RA: +18.355[2] mas/yr Dec.: +7.562[2] mas/yr |
| Parallax (π) | 3.4703±0.0825 mas[2] |
| Distance | 940 ± 20 ly (288 ± 7 pc) |
| Absolute magnitude (MV) | −1.76[6] |
| Details | |
| Mass | 1.7[8] M☉ |
| Radius | 122[9] R☉ |
| Luminosity | 1,672[2] L☉ |
| Surface gravity (log g) | 1.25[10] cgs |
| Temperature | 3,646[9] K |
| Metallicity [Fe/H] | −0.28[8] dex |
| Age | 224[10] Myr |
| Other designations | |
| c2 Cap, 47 Cap, AG Cap, BD−09°5833, HD 207005, HIP 107487, HR 8318, SAO 145648[11] | |
| Database references | |
| SIMBAD | data |
In 1963, Alan William James Cousins announced that 47 Capricorni is a variable star.[13] It was given its variable star designation in 1973.[14]
This is an aging red giant star with a stellar classification of M2III.[5] It is a semiregular variable star of subtype SRb with a period of 30.592 days and a maximum brightness of 5.9 magnitude.[3] With the supply of hydrogen at its core exhausted, the star has expanded to around 122 times the Sun's radius.[9] It is radiating 1,672 times the luminosity of the Sun[2] from its swollen photosphere at an effective temperature of 3,646 K.[9]