83 Leonis AB

The system is also known as Struve 1540 AB due to its observation and measurement as binary stars by Friedrich Georg Wilhelm von Struve (1793-1864). Struve became director of Russia's Dorpat Observatory in 1817 and founded and directed the Pulkovo Observatory in 1837, surveyed 120,000 stars from 1819 to 1827, published an extensive monograph of Halley's Comet based on observations in 1835 and his findings on 2,640 double stars in 1837, and measured the parallax of Vega from 1835 to 1838. While now often named in his honor, Struve's stars were originally numbered after the Greek letter "Sigma," so that this binary pair was originally designated as Sigma 1540 AB.

AB (wide) Binary Star System

According to the Sixth Catalog of Visual Orbits of Binary Stars, stars A and B are separated on average by 720 AUs (40.76" of a semi-major axis at 57.64 ly) in an eccentric orbit (e= 0.46) that may take around 32,000 years to complete. The catalog entry included a note that the "Hopmann orbit [was] rejected from Fourth Catalog ('period over 4000 years')." The orbit is inclined by 126.6° to Earth's line of sight (Josef Hopmann, 1960a; but older datum on angular separation appears to have been cited in Raghavan et al, 2006, see GJ 429 A and B in Table 2; and William Henry Smyth, 1844).

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	Orbital Distance (a=AUs)	Orbital Period (P=years)	Orbital Eccentricity (e)	Orbital Inclination (i=degrees)	Mass (Earths)	Diameter (Earths)	Density (Earths)	Surface Gravity (Earths)	Metallicity (Solar)
AB Mass Center	0.0	...	...	...	...	...	...	...	...
83 Leonis A	~345	~32,000	0.46	126.6	350-310,000?	207?	...	...	1.2-2.3
Inner H.Z. Edge A?	0.588	0.463	0	...	...	...	...	...	...
Outer H.Z. Edge A?	1.159	1.28	0	...	...	...	...	...	...
83 Leonis B	~375	~32,000	0.46	126.6	270,000	88.5	...	...	2.3
Planet "b"	0.122	0.047	0.13	?	=>27.6	>4	...	...	...
Disrupted H.Z.?	0.65	0.571	0.0	...	...	...	...	...	...
Planet "c"	5.4	13.1	~0.1	?	=>114	>9	...	...	...

83 Leonis A

Star A is a yellow-orange to orange-red subgiant that has been classed as yellow as G6 but as orange as K1 (i.e., spectral and luminosity type G6-K1 IV). The star may have a little more or less than a Solar-mass, as much as 1.9 times Sol's diameter (Pasinetti-Fracassini et al, 2001; and Johnson and Wright, 1983), and about 66 percent of its visual luminosity. It appears to be around 1.2 to 2.3 times as enriched as Sol with elements heavier than hydrogen and helium ("metallicity"), based on its relative abundance of iron to hydrogen (Cayrel de Strobel et al, 1991, HD 99491 on page 292; and based on Star B: (Meschiari et al, 2010, HD 99492 in Table 1 and on page 6; and Marcy et al, 2005, HD 99492 in Table 1). Useful star catalogue designations for 83 Leonis A include: 83 Leo A, HR 4414, Gl 429 A, Hip 55846, HD 99491, BD+03 2502, SAO 118864, FK5 1296, LHS 2407, LTT 13109, LFT 805, Wolf 393, STF 1540 A, and ADS 8162 A.

Habitable Zone around Star A

The NASA Star and Exoplanet Database has performed habitable zone calculations for 83 Leonis B that are more appropriate for a star with the luminosity of 83 Leonis A. Hence, Star A's habitable zone may range in orbital distance between 0.6 and 1.2 AUs. An Earth-type planet would have liquid water at around 0.87 AU -- between the orbital distances of Venus and Earth in the Solar System. At that distance from Star A and assuming a stellar mass of 0.95 Solar, such a planet would have an orbital period of over 300 days).

83 Leonis B

© Torben Krogh & Mogens Winther,


(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)



83 Leonis B is a orange-red
star that is similar in color to
Epsilon Eridani at left center
of meteor. (See a 2MASS
Survey image of 83 Leonis A
and B from the NASA Star
and Exoplanet Database.)

Star B is a orange-red main sequence dwarf of spectral and luminosity type K2 V (Meschiari et al, 2010, HD 99492 on page 6; and Marcy et al, 2005, HD 99492 in Table 1), previously ascertained by some to be a possible subgiant. The star has been most recently estimated to have 83 percent of Sol's mass (Meschiari et al, 2010, HD 99492 in Table 1; Takeda et al, 2007; and exoplanets.org), around 81 to 96 percent of its diameter (Meschiari et al, 2010, HD 99492 in Table 1; Pasinetti-Fracassini et al, 2001; and Johnson and Wright, 1983), and about 24 percent of its visual luminosity and 42 percent of its bolometric luminosity -- when accounting for infrared radiation (Meschiari et al, 2010, HD 99492 in Table 1). It may have around 2.3 times Sol's metallicity based on its relative abundance of iron and be around to six billion years old (Meschiari et al, 2010, HD 99492 in Table 1 and on page 6; and Marcy et al, 2005, HD 99492 in Table 1). Based on chromospheric activity, the star may have a rotational period of around 45 days (Meschiari et al, 2010, HD 99492 in Table 1 and on page 6; and Marcy et al, 2005, HD 99492 in Table 1). Useful star catalogue designations for 83 Leonis B include: 83 Leo B, Gl 429 B, Hip 55848, HD 99492, BD+03 2503, SAO 118865, LHS 2408, LTT 13110, LFT 806, Wolf 394, STF 1540 B, and ADS 8162 B.

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	Orbital Distance (a=AUs)	Orbital Period (P=years)	Orbital Eccentricity (e)	Orbital Inclination (i=degrees)	Mass (Earths)	Diameter (Earths)	Density (Earths)	Surface Gravity (Earths)	Metallicity (Solar)
83 Leonis B	0.0	...	...	...	270,000	88.5	...	...	2.3
Planet "b"	0.122	0.047	0.13	?	=>27.6	>4	...	...	...
Disrupted H.Z.?	0.65	0.571	0.0	...	...	...	...	...	...
Planet "c"	5.4	13.1	~0.1	?	=>114	>9	...	...	...

Habitable Zone around Star B

Planetary System around Star B

JPL, NASA



Larger image.



It is unknown whether planetary
candidate "b" is rocky or gaseous
like Neptune, but it appears to have
close to twice Uranus' mass.

Planet "b" - On January 2005, a team of astronomers (Geoffrey W. Marcy, R. Paul Butler, Steven S. Vogt, Debra Fischer, Gregory W. Henry, Greg Laughlin, Jason T. Wright, and John A. Johnson) announced the discovery of a planet around Star B (exoplanets.org; and Marcy et al, 2005). Designated "HD 99492 b," the planet is now calculated to have at least 27.6 times the mass of Earth -- nearly twice the mass of Uranus, and 8.7 +/- 0.6 percent of Jupiter's mass (Meschiari et al, 2010, HD 99492 in Table 2). It moves around 83 Leonis B at an average distance of only 0.122 AUs in a roughly circular orbit (e= 0.13 +/- 0.07) that takes only 17.054 +/- 0.003 days to complete (Meschiari et al, 2010, HD 99492 in Table 2).

NASA

Larger image.

Planetary candidate "c" is somewhat
more massive than Saturn.

Planet "c" - On November 17, 2010, a team of astronomers (including amateur astronomer, Peter Jalowiczor, who volunteered to analyze radial velocity data) submitted a pre-print on the detection of a second giant planet "c" around Star B with at least 114 Earth-masses (Meschiari et al, 2010; and Colin Drury, The Star, December 27, 2010). Planet c is now calculated to have at least 114 times the mass of Earth -- 36 +/- 6 percent of Jupiter's mass (Meschiari et al, 2010, HD 99492 in Table 2). It moves around 83 Leonis B at an average distance of 5.4 +/- 0.5 AUs in a roughly circular orbit (e= 0.1 +/- 0.2) that takes over 13.1 years (or 4,790 +/- 744 days) to complete (Meschiari et al, 2010, HD 99492 in Table 2).

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