HD 49933 (HR 2530) is a binary star system in the equatorial constellation of Monoceros, the unicorn. The HD designation indicates the identifier of the star found in the Henry Draper catalogue. At an apparent magnitude of 5.8,[2] this star can just be seen with the naked eye under suitably dark conditions. Based upon parallax measurements from the Hipparcos mission,[11] the distance to HD 49933 is about 97 light-years (30 parsecs) with a 1% margin of error.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Monoceros |
| Right ascension | 06h 50m 49.83180s[1] |
| Declination | –00° 32′ 27.1701″[1] |
| Apparent magnitude (V) | 5.781[2] |
| Characteristics | |
| HD 49993 A | |
| Spectral type | F2 V[3] |
| U−B color index | –0.07[4] |
| B−V color index | +0.39[4] |
| HD 49993 B | |
| Spectral type | M0[5] |
| Astrometry | |
| Radial velocity (Rv) | –14.7[6] km/s |
| Proper motion (μ) | RA: +22.09[1] mas/yr Dec.: –186.51[1] mas/yr |
| Parallax (π) | 33.69 ± 0.42 mas[1] |
| Distance | 97 ± 1 ly (29.7 ± 0.4 pc) |
| Absolute magnitude (MV) | 3.42[2] |
| Position (relative to HD 49933 A)[5] | |
| Component | HD 49933 B |
| Epoch of observation | 2016 |
| Angular distance | 6.5″ |
| Position angle | 23° |
| Projected separation | 190 AU |
| Details | |
| Mass | 1.079 ± 0.073[7] M☉ |
| Radius | 1.385 ± 0.031[7] R☉ |
| Luminosity | 3.47 ± 0.18[7] L☉ |
| Surface gravity (log g) | 4.08[8] cgs |
| Temperature | 6,598[8] K |
| Metallicity [Fe/H] | –0.29[8] dex |
| Rotational velocity (v sin i) | 10[9] km/s |
| Age | 2.4[2] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 49933 A
Its primary HD 49993 A is a Sun-like[7] star. This is an F-type main sequence star with a stellar classification of F2 V,[3] where the luminosity class V indicates that it is generating energy through the nuclear fusion of hydrogen at its core. It is slightly larger than the Sun, with 108% of the Sun's mass and 139% of the Sun's radius. HD 49933 A emits 3.47 times as much energy as the Sun from its outer atmosphere at a higher effective temperature of about 6,598 K,[7] giving it the yellow-white hue of an F-type star.[12] It is estimated to be 2.4 billion years old.[2]
The surface magnetic activity on this star is similar to what is observed on the Sun. Magnetic features on the surface have been detected using asteroseismology that appear to be starspots (the stellar equivalent to sunspots on the Sun).[13]
HD 49933 B
In 2008 it was discovered the primary star has an 11.3 magnitude common proper motion companion at an angular separation of 5.9 arcseconds, which may make this a binary star system if the pair are gravitationally bound.[14] In 2016, it was confirmed that HD 49933 A is orbited by a red dwarf star of spectral class M0.[5]