p Eridani 3?
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© Torben Krogh & Mogens Winther,
(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)
p Eridani A and B are orange-red
dwarf stars, like Epsilon Eridani
at left center of meteor. (See a
Digitized Sky Survey image
of p Eridani from the
Nearby Stars Database.)
The p Eridani system is located only about 26.6 light-years (ly) away from Sol. It lies in the southwest corner (01:39:47.2-56:11:44 for Star A and 01:39:47.7-56:11:34 for Star B, ICRS 2000.0) of Constellation Eridanus, the River -- north of Achernar (Alpha Eridani). While the system is already a confirmed visual binary, spectroscopic analysis suggests that Star B may have an additional, dim companion.
This main sequence, orange-red dwarf (K2-5 V) may have only about 88 percent of Sol's mass (Christopher J. Corbally, 1984, page 14), 79 percent of its diameter, and 28 percent of its luminosity. The distance from p Eridani A where an Earth-type planet would be "comfortable" with liquid water is centered around 0.53 AU -- between the orbital distances of Mercury and Venus in the Solar System. At that distance from the star, such a planet would have an orbital period of almost 150 days, or less than half of an Earth year. Some alternative useful star catalogue numbers for the star are: p Eri, HR 487, Gl 66 A, Hip 7751, HD 10361, CD-56 328 A, CP(D)-56 329 A, SAO 232490, LTT 902, and Dunlop 5 A. (The SIMBAD Astronomical Database provides a double/multiple system identification -- "HD 10360 J" -- for an object query using Gl/GJ 66, instead of individual queries for HR 486 and 487.)
According to the new Sixth Catalog of Orbits of Visual Binaries, stars A and B are separated by an "average" distance of about 63.7 AU (semi-major axis of 7.817" using a HIPPARCOS parallax of 0.122275 +/- 0.00141"). The two stars move in a highly elliptical orbit (e=0.534) that swings them between 29.7 and 97.7 AUs apart and takes about 484 years to complete, and is inclined at 142.8° from the perspective of an observer on Earth (G.B. van Albada, 1957). (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.)
This main sequence, orange-red dwarf (K0-3 V) may have only about 86 percent of Sol's mass (Corbally, 1984, page 14), six tenths of its diameter, and 25 percent of its luminosity. The distance from p Eridani B where an Earth-type planet would be "comfortable" with liquid water is centered around 0.50 AU -- between the orbital distances of Mercury and Venus in the Solar System. At that distance from the star, such a planet would have an orbital period of almost 139 days, or less than half of an Earth year. Some alternative useful star catalogue numbers for the star are: HR 486, Gl 66 B, HD 10360, CD-56 329 or CD-56 328 B, CP(D)-59 328 or CP(D)-56 329 B, SAO 232492, LTT 903, and Dunlop 5 B.
The Yale Bright Star Catalogue indicates that HR 486 (p Eridani B) has a spectroscopic companion.
Hunt for Substellar Companions
Astronomers would find it very difficult to detect Earth-type planets around p Eridani A and B using present methods.
The following star systems are located within 10 ly of p Eridani.
|Star System||Spectra &|
|CD-68 47||K0 V||5.4|
|Zeta Tucanae 2?||F8-G0 V |
|L 362-81||DA5 /VII||9.5|
|Gliese 86||K0-1 V||9.8|
|Beta Hydri||G1-2 IV||10.0|
Up-to-date technical summaries on this star can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS for Star A and Star B, the Nearby Stars Database, and the Research Consortium on Nearby Stars (RECONS). Additional information may be available at Roger Wilcox's Internet Stellar Database.
Eridanus, the river, wends its way from the Hunter's foot of Orion then southwest to the southern circumpolar zone to enclose a larger area of sky than any other constellation. For more information on stars and other objects in Constellation Eridanus and an illustration, go to Christine Kronberg's Eridanus. For another illustration, see David Haworth's Eridanus.
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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