Gamma Leporis 3?

Gamma Leporis A

This star is a main-sequence white-yellow dwarf star of spectral and luminosity type F6-7 V. Gamma Leporis has about 1.2 times Sol's mass, about 1.3 times its diameter, and about 2.6 times of its luminosity. It appears to be less enriched than Sol in elements heavier than hydrogen ("metals") with about 72-89 percent of Sol's abundance of iron (Cayrel de Strobel et al, 1991, page 12). The star may be about 2.7 billion years old (Edvardsson et al, 1993, page 22). The star and its known stellar companion B have an observed separation of about 864 AU (96.3" at a HIPPARCOS parallax of 0.11149 +/- 0.00060"), but there may be as many as two optical companions. Useful star catalogue numbers for Gamma Leporis A include: Gam Lep, 13 Lep, HR 1983, Gl 216 A, Hip 27072, HD 38393, BD-22 1211, CD-22 2438, CP(D)-22 886, SAO 170759, FK5 217, LTT 2364, and ADS 4334.

Gamma Leporis B

© Torben Krogh & Mogens Winther,

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


Gamma Leporis B may be an orange-
red dwarf star, like Epsilon Eridani
at left center of meteor.

Gamma Leporis C?

NASA's NStars Database (see NS 0544-2226) suggests that this system may have a third component.

According to a University of Wisconsin's Niagra Query Engine entry, LDS 846 was announced as a possible companion by George A. Van Biesbroeck (1880-1974) at the Victoria Double Star Conference in 1956 (16th magnitude, red, 1130" distant in 67 degrees and included as Gamma Leporis C in Luyten's LTT catalogue as LTT 2368). Although the published proper motion was given as 0.63" in 210 degrees (later measures -- University of Wisconsin? -- "on Palomar survey plates with an interval of 15 years, give 0.63" in 207 degrees thus fully confirming van Biesbroek's measure"), the proper motion of Gamma Leporis itself is given as 0.47" in 219 degees, and its parallax as 0.122". Hence, the minimum separation of the C component from the brighter pair is around the order of 9,000 AUs, and "... the parabolic velocity of the companion would at most be 0.7 km/sec, assuming a total mass of 2.5 for the triple system." Because the minimum observed velocity must be six km/sec, and Gamma Leporis AB and "VBs 1" do not appear to be physically connected despite the close similarity of direction in their motions.

Hunt for Substellar Companions

A 2.5-year search analyzing radial velocities failed to find a large Jupiter or brown dwarf within 10 AUs of Gamma Leporis A (Murdoch et al, 1993). The distance from Gamma Leporis A where an Earth-type planet would be "comfortable" with liquid water may be centered around 1.6 AU -- just outside the orbital distance of Mars in the Solar System with an orbital period of 1.85 Earth Years. An Earth-type planet around Star B may be centered around 0.50 AUs -- which between the orbital distances or Mercury and Venus -- with an orbital period of about 161 days, or almost half an Earth year. At such close distances to either star, astronomers would have great difficulty in detecting Earth-type planets using present methods.

Astronomers are hoping to use NASA's Terrestrial Planet Finder (TPF) and the ESA's Darwin planned groups of observatories to search for a rocky inner planet in the so-called "habitable zone" (HZ) around Gamma Leporis A. As currently planned, the TPF will include two complementary observatory groups: a visible-light coronagraph to launch around 2014; and a "formation-flying" infrared interferometer to launch before 2020, while Darwin will launch a flotilla of three mid-infrared telescopes and a fourth communications hub beginning in 2015.