Iota Pegasi 2
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This star system is located about 38.4 light-years (ly) away from our Sun, Sol. It lies in the northwestern corner (22:7:0.7+25:20:42.4, ICRS 2000.0) of Constellation Pegasus, the Winged Horse, -- northwest of Lambda, Mu, Alpha (Markab), and (Homam) Zeta Pegasi; southwest of Stephan's Quintet and Eta (Matar) and Beta Pegasi (Scheat); southeast of the Lacework Nebula (NGC 6960), northeast of Enif (Epsilon Pegasi), Globular Cluster M15, and Kitalpha (Alpha Equulei); and north of Biham (Theta Pegasi) and Sadalmelik (Alpha Aquarii). The system was discovered to have a close-orbiting spectrocopic binary companion by Campbell near the end of the Nineteenth Century (Fekel and Tomkin, 1983; and William W. Campbell, 1899), which is visible in red wavelengths. Its dim neighbor (WDS J22070+2521 B) at a wide separation of 123.7 arc-seconds, however, is probably an optical companion. (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.)
Iota Pegasi A
Star A is a main sequence dwarf star of spectral and luminosity type F5 V (NASA Stars and Exoplanet Database). The star may have around 1.25 to 1.33 times Sol's mass (Jancart et al, 2005, page 14 under HIP 109176; Nordström et al, 2004; Boden et al, 1999; NASA Stars and Exoplanet Database; and David F. Gray, 1992; and Fekel and Tomkin, 1983), around 1.4 to 1.5 times Sol's diameter based on a power-law estimate (van Belle and von Braun, 2009, page 7, Table 4; NASA Stars and Exoplanet database; and Kenneth R. Lang, 1980); and around 3.3 times its theoretical bolometric luminosity (NASA Stars and Exoplanet database; and Kenneth R. Lang, 1980). Based on the stars' lithium abundance, their probable spectral type, and close-orbiting nature, they may be 80 to 600 million years old (Fekel and Tomkin, 1983; and Edvardsson et al, 1993, page 122 for HR 799), but some believe the system to be 2.5 billion years old (Nordström et al, 2004). The star may only be around 0.79 to 1.26 times as enriched as Sol with elements heavier than hydrogen ("metallicity") based on its abundance of iron (Nordström et al, 2004; and Cayrel de Strobel et al, 1991, page 310). Star A has been designated NSV 14034 as a New Suspected Variable star. Useful star catalogue numbers for the star include: Iot Peg A, 24 Peg, HR 8430, Gl 848 A, HIP 109176, HD 210027, BD+24 4533 A, SAO 90238, FK5 831, and LTT 16472.
According to the Ninth Catalogue of Spectroscopic Binary Orbits (for HD 210027), Stars A and B move around each other at an average distance of only 0.051 AUs (semi-major axis a=0.00407 +/- 0.27") in a highly circular (e~0) orbit that takes just 10.2 days to complete. Their orbit around each other is inclined by 80 +/-13° with respect to an observer on Earth (Tokovinin et al, 2006; Jancart et al, 2005, pp. 9-14; Boden et al, 1999; Fekel and Tomkin, 1983; Abt and Levy, 1976; Petrie and Phibbs, 1949; and Heber D. Curtis, 1904). (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.)
The orbital distance from Stars A and B where an Earth-type planet currently would be "comfortable" with liquid water is centered near 1.8 AU -- between the orbital distances of Mars and the Main Asteroid Belt in the Solar System. At that distance from the star, such a planet would have an orbital period over 2.1 years. Such a planet would be very difficult for astronomers to detect with today's astronomical instruments and methods.
Iota Pegasi B
Star b is a main sequence dwarf star of spectral and luminosity type G8 V (Fekel and Tomkin, 1983). It has 80 to 82 percent of Sol's mass (Jancart et al, 2005, page 14 under HIP 109176; Boden et al, 1999; and Fekel and Tomkin, 1983), smaller than Solar diameter, and less than Solar luminosity. Useful star catalogue numbers for this star include: Iot Peg B, HD 210027 B, BD+24 4533 B, CSI+24 4533 2, CCDM J22070+2520 A, and IDS 22023+2452 A.
The following star systems are located within 10 light-years, plus more bright and notable stars within 10 to 20 ly, of Iota Pegasi.
|Star System||Spectra &|
|Ross 271||M2 Ve||4.7|
|L 1363-3||DQ6 /VII||5.9|
|LP 397-34||M V||6.1|
|BD+27 4120 AB||M0 Ve |
|AC+17 536-125||M2 Ve||6.8|
|G 188-38||M V||9.3|
|* plus bright and notable stars *||. . .||. . .|
|Hip 109119||A2 V||10|
|51 Pegasi||G4-5 V||15|
|85 Pegasi AabB||G3-5 V |
|Wolf 940||M3.5-4 V||18|
|Xi Pegasus 2?||F6-7 V-III |
Up-to-date technical summaries on this stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARCNS, the NASA Stars and Exoplanet Database; and SIMBAD. Additional information may be available at Roger Wilcox's Internet Stellar Database, www.alcyone.de's page for Iota Pegasi, and more recent research papers may become available at the SAO/NASA ADS.
The "Winged Horse" is one of the larger constellations of the Northern Hemisphere. For more information and an illustration of the constellation, go to Christine Kronberg's Pegasus. For another illustration, see David Haworth's Pegasus.
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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