11 (SV) Leonis Minoris AB

11 Leonis Minoris A

Star A is probably a yellow-orange main sequence dwarf of spectral and luminosity type G8 Vv, although it has been classified as orange as K0 and as bright as a subgiant (IV) or even giant (III) for many decades (SIMBAD; and Olin J. Eggen, 1956: page 419). As a main sequence dwarf with sub-Solar luminosity, the star may have a mass around 86 percent of Sol's based on an interpolation table (NASA Stars and Exoplanet Database; and Gray et al, 2003). The star's diameter is uncertain, with estimates ranging from 85 to 144 percent of Sol's diameter but the power law estimate is 1.03 +/- 0.05 (NASA Stars and Exoplanet Database; Fracassini et al, 1994; Johnson and Wright, 1983, page 667; and Kenneth R. Lang, 1980). Its bolometric luminosity has been estimated to be around 78 percent of Sol's visual luminosity (NASA Stars and Exoplanet Database; and Kenneth R. Lang, 1980). It appears to be as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Cayrel de Strobel et al, 1991: page 289). The star is chromospherically active with star spots that may cover more than 15 percent of its surface during one observed period, and its light-curve variability has a period of around 18 days, whose mechanism is apparently due to rotational modulation of active starspots (Skiff and Lockwood, 1986). Useful catalogue numbers and designations for the star include: 11 LMi, SV LMI, Gl 356 A, HR 3815, HD 82885, Hip 47080, BD+36 1979, SAO 61586, LHS 2156, LTT 12535, LFT 659, USNO 832, and ADS 7441 A.

According to the Sixth Catalog of Orbits of Visual Binaries, Stars A and B move around each other at an average distance of 43.0 AUs (semi-major axis a= 3.84") in an extremely eccentric (e= 0.88) orbit that takes 201 years to complete. The two stars get as close as 5.2 AUs and as far away from each other as 80.8 AUs, and their orbits around each other is inclined by 117° with respect to an observer on Earth. Based on those orbital characteristics estimated in 1988, the mass ratio was calculated to be f=0.20 (Wulff-Dieter Heintz, 1988: pp. 543 and 545, see ADS 7441). (See an animation of the orbits of Stars A and B and their potentially habitable zones, with a table of basic orbital and physical characteristics.)

An Earth-type planet could have liquid water in a stable orbit centered around 0.88 AU from Star A (but ranging between -- between the orbital distances of Venus and Earth in the Solar System. Such a planet would have an orbital period around 326 days (almost nine-tenths of an Earth year). It would, however, be difficult to detect using present astronomical methods and equipment.

NASA -- larger image

11 Leonis Minoris B is a dim red dwarf star, like
Gliese 623 A (M2.5 V) and B (M5.8Ve) at lower right.

11 Leonis Minoris B

Star B is a main sequence, red dwarf star of spectral and luminosity type M 5V. Much smaller and dimmer than Sol, the star may have around 0.2 Solar-mass, 24 percent of its diameter (Johnson and Wright, 1983, page 667), and only 66 of 100,000 of its visual luminosity. Useful catalogue numbers and designations for the star include: 11 LMi B, Gl 356 B, HR 3815 B, HD 82885 B, and BD+36 1979 B. An Earth-type planet could have liquid water in a stable orbit centered around 0.03 AU from Star B -- well within the orbital distance of Mercury in the Solar System. Such a planet would have an orbital period slightly over four days and would be tidally locked with respect to Star B. Such a planet would be difficult to detect using present astronomical methods and equipment.