15 Canis Majoris
Variable star in the constellation Canis Major
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15 Canis Majoris is a variable star in the southern constellation of Canis Major,[9] located roughly 1,200 light years away from the Sun.[2] It has the variable star designation EY Canis Majoris; 15 Canis Majoris is the Flamsteed designation. The star is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of +4.8. It is moving away from the Earth with a heliocentric radial velocity of 28 km/s.[8]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 06h 53m 32.907s[2] |
| Declination | â20° 13â² 27.32â³[2] |
| Apparent magnitude (V) | +4.79 â 4.84[3] |
| Characteristics | |
| Spectral type | B1IV[4] |
| UâB color index | â0.96[5] |
| BâV color index | â0.212±0.013[6] |
| Variable type | β Cep[7][3] |
| Astrometry | |
| Radial velocity (Rv) | 28.00[8] km/s |
| Proper motion (μ) | RA: â5.46±0.16[2] mas/yr Dec.: +3.58±0.17[2] mas/yr |
| Parallax (Ï) | 2.68±0.24 mas[2] |
| Distance | 1,200 ± 100 ly (370 ± 30 pc) |
| Absolute magnitude (MV) | â3.02[6] |
| Details[7] | |
| Mass | 12.8±1.2 Mâ |
| Radius | 6.8±1.2 Râ |
| Luminosity | 20,000+12,000 â7,400 Lâ |
| Surface gravity (log g) | 3.89±0.20 cgs |
| Temperature | 26,100±1,200 K |
| Rotational velocity (v sin i) | 20±12 km/s |
| Other designations | |
| 15 CMa, EY CMa, BDâ20°1616, FK5 2532, GC 9034, HD 50707, HIP 33092, HR 2571, SAO 172520[9] | |
| Database references | |
| SIMBAD | data |
This is a B-type star with a stellar classification of B1 IV.[4] Merle F. Walker discovered that 15 Canis Majoris is a variable star in 1955, and he published that discovery in 1956.[10] It is classified as a Beta Cephei type variable star and its brightness varies from magnitude +4.79 down to +4.84 with a period of 4.430 h.[3] The star has 12.8 times the mass of the Sun and 6.8 times the Sun's radius. It is radiating 20,000 times the luminosity of the Sun from its photosphere at an effective temperature of 26,100 K.[7]