Rho Leonis

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Rho Leonis
Diagram showing star positions and boundaries of the Leo constellation and its surroundings
Cercle rouge 100%.svg

Location of ρ Leonis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 10h 32m 48.67168s[1]
Declination +09° 18′ 23.7094″[1]
Apparent magnitude (V) 3.870[2]
Characteristics
Spectral type B1 Iab[3]
U−B color index –0.945[4]
B−V color index –0.153[4]
Astrometry
Radial velocity (Rv) +42.0[5] km/s
Proper motion (μ) RA: –5.93 ± 0.20[1] mas/yr
Dec.: –3.40 ± 0.11[1] mas/yr
Parallax (π) 0.60 ± 0.18[1] mas
Distance approx. 5,000 ly
(approx. 1,700 pc)
Absolute magnitude (MV) –6.8[6]
Details
Mass 27.1 ± 8.4[7] M☉
Radius 37.4[8] R☉
Luminosity 295,000[6] L☉
Surface gravity (log g) 3.09[9] cgs
Temperature 24,200[9] K
Metallicity [Fe/H] –0.89[9] dex
Rotation 7 ± 2 days[10]
Rotational velocity (v sin i) 60[11] km/s
Age 4.5 ± 0.1[7] Myr
Other designations
47 Leo, HR 4133, BD+10 2166, HD 91316, SAO 118355, FK5 396, HIP 51624.
Database references
SIMBAD data

Rho Leonis (ρ Leo) is a binary star in the zodiac constellation of Leo, and, like the prominent nearby star Regulus, it is located near the ecliptic. With an apparent visual magnitude of 3.9,[4] this star can be readily seen with the naked eye at night. Parallax measurements give a distance estimate of about 5,400 light-years (1,700 parsecs) from the Earth.[12]

This is an enormous star with about 21 times the Sun's mass (M☉)[13] and 37 times the Sun's radius.[8] Its spectrum matches a stellar classification of B1 Iab,[3] with the 'Iab' luminosity class indicating that it is in the supergiant stage of its evolution. Rho Leonis is radiating about 295,000 times the Sun's luminosity[6] at an effective temperature of 24,200 K,[9] giving it the blue-white hue typical of a B-type star. A strong stellar wind is expelling mass from the outer envelope at a rate of 3.5 × 10−7 M☉ per year, or the equivalent of 1 M☉ every 2.8 million years.[8] The rotation rate is probably about once per 7 days, with an upper limit of 47 days.[10]

Rho Leonis is classified as a runaway star, which means it has a peculiar velocity of at least 30 km s−1 relative to the surrounding stars. It has radial velocity of 42 km s−1 away from the Sun and a proper motion that is carrying it about 1.56 Astronomical Units per year, equivalent to 7 km s−1,[14] in a transverse direction. The star is situated about 2,300 light-years (710 parsecs) above the galactic plane.[15]

Rho Leo is sometimes occulted by the moon and unusual light variation during these occultations has been explained as the result of a possible close companion. The companion would be just over one magnitude fainter and separated by 0.01 arcsec.[16] The companion has not been detected by any other means although it should be easily detected with modern observations.[17]

References

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External links

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  14. ↑ An Astronomical Unit (AU) is 1.5 × 108 km, while a year is 3.2 × 107 seconds. Thus, 1.56 AU/year = (1.56 AU/yr) × (1.5 × 108 km/AU) / (3.2 × 107 s/yr) = 7 km/s.
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