Rho Leonis

ρ Leonis (Latinized to Rho Leonis, abbreviated ρ Leo, Rho Leo) is the star's Bayer designation.

Rho Leonis has the traditional Chinese name Shaomin (少民); it and ο Leonis (Taimin, 太民) are the two southernmost stars of the Xuanyuan (轩辕) constellation. The IAU Working Group on Star Names approved the name Shaomin for ρ Leonis on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names; ο Leonis has the IAU-approved name Subra.^[9]

The spectrum of Rho Leonis matches a stellar classification of B1 Iab,^[4] with the 'Iab' luminosity class indicating that it is a supergiant star. Rho Leonis is a former red supergiant that shifted back to hotter temperatures, being in the evolutionary stage known as blue loop.^[3]

This is an enormous star with about 20 times the Sun's mass (M_☉) and 28 times the Sun's radius (R_☉). Rho Leonis is radiating about 150,000 times the Sun's luminosity (L_☉) at an effective temperature of 21,700 K,^[7] 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.^[12] The rotation rate is about once per 12.5 days. The star rotates at an angle of 21.7°+0.5°
−0.4° relative to Earth.^[3]

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,^[a] in a transverse direction. The star is situated about 2,300 light-years (710 parsecs) above the galactic plane.^[13]

The star is 0.15 degree north of the ecliptic, so it can be occulted by the moon.^[14] Unusual light variation during these occultations has been explained as the result of a possible close companion, which would be just over one magnitude fainter and separated by 0.01 arcsec.^[15] It has not been detected by any other means although it should be easily detected with modern observations.^[16] Speckle interferometry observations made during 2009 to 2023 did not detect the companion, strongly indicating that it does not exist.^[17] However, there is evidence for a companion from spectroscopic observations, which could be interpreted as radial pulsations or the presence of a secondary star that periodically exchange mass with the primary and has its own circumstellar disk.^[3]