11 (SV) Leonis Minoris AB
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11 Leonis Minoris A is a yellow-orange star that is dimmer,
cooler, and more orange in color than our Sun, Sol, and
its stellar companion B is even dimmer, cooler, and more
reddish. (See Sloan Digital Sky Survey field images of
the 11 Leonis Minoris system from WikiSky.org.)
The 11 Leonis Minoris system is located about 36.5 light-years (ly) from Sol. It lies at the east central part of (9:35:39.5+35:48:36.5, ICRS 2000.0) of Constellation Leo Minor, the Lesser Lion -- east of Alpha Lyncis, north of Rasalas (Mu Leonis) and Zosma (Delta Leonis), west of Beta Leonis Minoris and Praecipua (46 Leonis Minoris) and Alpha Leonis Minoris as well as Alula Australis (Xi Ursae Majoris) and Alula Borealis (Nu Ursae Majoris), and southwest of Tania Borealis (Lambda Ursae Majoris) and Tania Australis (Mu Ursae Majoris). With an active chromosphere and a (sometimes eccentrically close) binary stellar companion, the star is considered to be a RS Canum Venaticorum (RS CVn) type variable with the variable star designation of SV Leonis Minoris. (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.)
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). The star's diameter is uncertain, with estimates ranging from 85 to 144 percent of Sol's diameter (Fracassini et al, 1994; and Johnson and Wright, 1983, page 667). Its typical luminosity has been measured to be around 71 percent of Sol's visual luminosity. As a main sequence dwarf with sub-Solar luminosity, the star should have a mass less than Sol's (i.e., between 0.9 and 1 Solar-mass). 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 0.84 AU from Star A -- between the orbital distances of Earth and Mars in the Solar System. Such a planet would have an orbital period around 290 days (around 80 percent 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.
The following table includes all star systems known to be located within 10 light-years (ly), plus more bright stars within 10 to 20 ly, of 11 Leonis Minoris AB.
|Star System||Spectra &|
|BD+36 1970||M0-2 V||7.6|
|GJ 1134||M V||8.2|
|GJ 1119||M V||8.5|
|55 (Rho1) Cancri AB||G8-K0 V |
|Ross 92||M4 V||9.5|
|G 42-24||M V||9.7|
|GJ 1138||M V||9.7|
|* plus bright stars *||. . .|
|20 Leonis Minoris||G1-3 Va||13|
|Theta Ursae Majoris 3||F6 IV |
|Talitha 4||A7 IV |
|47 Ursae Majoris||G0-1 V||15|
|61 Ursae Majoris||G8 Ve||16|
|36 Ursae Majoris 3?||F8 V||16|
|Alula Australis 4||F8.5-G0 Ve |
|Groombridge 1830||G8 VIp||17|
|HR 3579 A?||F5 V |
Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARCNS for Star A and Star B, and SIMBAD. Additional information may be available at Roger Wilcox's Internet Stellar Database, and from www.alcyone.de for SV Leonis Minoris. New research papers may eventually become availableat the SAO/NASA ADS.
Leo Minor, the "Lesser Lion," is a small, faint, and relatively modern constellation. It was of the seven constellations (including Canes Venatici, Lacerta, Lynx, Scutum, Sextans, and Vulpecula) introduced by Johannes (John or Jan) Hevelius (1611-1687) in a catalogue published posthumously in 1690. The constellation represents the Lion that Hercules had to kill as one of his 12 tasks. For more information and an illustration of the constellation, go to Christine Kronberg's Leo Minor. For another illustration, see David Haworth's Leo Minor.
For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.
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