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This star system is located about 38.3 light-years (ly) away from our Sun, Sol. It lies in the central region (15:46:26.6+7:21:11.1, ICRS 2000.0) of Constellation Serpens, the Serpent, in its head portion (Serpens Caput) on the west side of Constellation Ophiuchus -- just slightly northeast of Unukalhai, (Alpha Serpentis); south of Beta Serpentis; northwest of Lambda (Marfik) and Kappa Ophiuchi; southeast of Delta, Gamma, Alpha (Alphecca), and Beta (Nusakan) Coronae Borealis; and southwest of Gamma Herculis and Kornephoros (Beta Herculis). Despite suspicion of a single-lined spectroscopic binary companion, no stellar or substellar objects have been confirmed (more below).
Lambda Serpentis is a main sequence dwarf star of spectral and luminosity type G0 V, but it is listed as a possible subgiant in some catalogues. The star may have around 1.01 to 1.28 times Sol's mass (Yoichi Takeda, 2007; Valenti and Fischer, 2005; Klaus Fuhrmann, 1998, page 166; and NASA Stars and Exoplanet Database; and David F. Gray, 1992), around 1.33 to 1.39 times Sol's diameter (Klaus Fuhrmann, 1998, page 166; NASA Stars and Exoplanet database; and Kenneth R. Lang, 1980); and around 1.9 to 2.2 times its bolometric luminosity (Klaus Fuhrmann, 1998, page 166 for absolute bolometric magnitude; NASA Stars and Exoplanet database; and Kenneth R. Lang, 1980). It may be around 4.6 to 7.2 billion years old (Nordstrom et al, 2004; and Edvardsson et al, 1993, page 124 for HR 5868). The star may only be around 66 to 141 percent as enriched as Sol with elements heavier than hydrogen ("metallicity") based on its abundance of iron (NASA Stars and Exoplanet database; Valenti and Fischer, 2005; Takeda et al, 2002; and Cayrel de Strobel et al, 1991, page 299). No magnetic field on the star's surface has been detect (Savanov and Savel'Eva, 2008). Although it appears to be a chromospherically inactive star with a rotational period of 26 days (Cumming et al, 1999, page 902 under HR 5868), it has been designated SV ZI 1157 as a Suspected Variable star as well as NSV 7246, as a New Suspected Variable star (M. Petit, 1990). Useful star catalogue numbers for the star include: Lam Ser, 27 Ser, HR 5868, Gl 598, HIP 77257, HD 141004, BD+07 3023, SAO 121186, and LTT 14677.
The orbital distance from Lambda Serpentis where an Earth-type planet currently would be "comfortable" with liquid water is centered near 1.4 AU -- just inside the orbital distance of Mars in the Solar System. At that distance from the star, such a planet would have an orbital period around 1.5 years (563 days). It would be very difficult for astronomers to detect with today's astronomical instruments and methods.
Hunt for Companion Objects
The star was suspected of having a single-line spectroscopic binary companion with a period of 1,837 days -- over five years (Abt and Levy, 1976, page 288), but the results were contested (Morbey and Griffin, 1987, page 349). As CORVAL monitoring failed to detect significant radial velocity variations over period of 3,400 days -- or over 9.3 years (Duquennoy and Mayor, 1991, pp. 492 and 506), the detection is now considered to be spurious.
The following star systems are located within 10 light-years, plus more bright stars within 10 to 20 ly, of Lambda Serpentis.
|Star System||Spectra &|
|Gamma Serpentis||F6 V||6.0|
|Ross 508||M4 V||8.0|
|LP 625-34||M V||9.5|
|BD+21 2763||M0-9 Ve||9.8|
|* plus bright stars *||. . .|
|Psi Serpentis 3?||G2.5-5 V |
|18 Scorpii||G1-5 V-Va||15|
|L 989-20 AB||G-M3.5 V |
|Chien 414||F2 V||17|
|Zeta Herculis AB||F9-G0 IV |
|Xi Bootis 3?||G8 Ve |
|Muphrid AB||G0 V |
|39 Serpentis 3?||G0-1 IV |
Up-to-date technical summaries on this star can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS; the NASA Stars and Exoplanet Database; and SIMBAD. Additional information may be available at Roger Wilcox's Internet Stellar Database and from www.alcyone.de as Lamdba Serpentis. More recent research papers may become available at the SAO/NASA ADS.
Constellation Serpens is composed of two parts: Serpens Caput (the Head of the Serpent) and Serpens Cauda (the Tail). Separating them is Constellation Ophiuchus, the Serpent Holder. For more information on stars and other objects in this Constellation, go to Christine Kronberg's Serpens.
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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