BD-05 1844 / Gl 250 AB
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© Torben Krogh & Mogens Winther,
(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)
BD-05 1844 A is an orange-red dwarf
star, like Epsilon Eridani at left
center of meteor. (See a Digitized
Sky Survey image of BD-05 1844
(HR 5568) from the Nearby Stars Database.)
This binary star system is located 28.4 (ly) away from Sol. It lies in the east central part (6:52:18.1-5:10:25.4 for Star A and 6:52:18-5:11.4 for Star B, ICRS 2000.0) of Constellation Monoceros, the Unicorn -- northeast of M50, west of M48, south of Delta Monocerotis, southwest of Procyon, and east of the Great Nebula in Orion. Many astronomers now refer to this star system by its designation in the famous Gliese Catalogue of Nearby Stars (CNS, now ARICNS database) of Wilhelm Gliese (1915-93), who was a longtime astronomer at the Astronomiches Rechen-Institut at Heidelberg (even when it was at Berlin).
The system's designation of BD-05 1844 comes from a catalogue that was originally published in 1863 by Friedrich Wilhelm August Argelander (1799-1875) on the position and brightness of 324,198 stars between +90° and -2° declination that were measured over 11 years from Bonn, Germany with his assistants Eduard Schönfeld (1828-1891) and Aldalbert Krüger (1832-1896). The catalogue became famous as the Bonner Durchmusterung ("Bonn Survey") and is typically abbreviated as BD. It was later expanded and extended during the early 20th Century with the Cordoba (observed from Argentina) then the Cape Photographic Durchmusterung (observed from South Africa).
This main sequence, orange-red dwarf (K3 V) may have 80 percent of Sol's mass, 78 percent of its diameter (Johnson and Wright, 1983, page 661), and 14.6 percent of its luminosity. According to the Astronomiches Rechen-Institut at Heidelberg's ARICNS entry for Gl 250 B, the star has a binary companion "B" at a separation of a bit over 500 AUs -- 58" at 177° using a HIPPARCOS distance estimate of 23.38 ly (Olin Jeuck Eggen, 1955, page 416 -- see "1606").
Star A's late spectral type and dim luminosity puts it possibly close to the lower limit of habitability for (multicellular) Earth-type plant and animal life, given the redness of its light and the increased risk of tidal locking from the closeness of the orbit necessary for liquid water on a planetary surface. The distance from Star A where an Earth-type planet would be "comfortable" with liquid water is centered around 0.382 AU -- just within the orbital distance of Mercury in the Solar System. At that distance from the star, such a planet would have an orbital period of 96.2 days, or just over a quarter of an Earth year. Some alternative useful star catalogue numbers for the star are: Gl 250 A, Hip 32984, HD 50281, SAO 133805, LHS 1875, LTT 2662, LFT 494, and LPM 244.
This is a a red dwarf of spectral and luminosity type M2.5 V. It has about 50 percent of Sol's mass, 49 percent of its diameter(Johnson and Wright, 1983, page 661), and 58/10,000th of its brightness.
NASA -- larger image
BD-05 1844 B is a dim red dwarf star, like
Gliese 623 A (M2.5V) and B (M5.8Ve) at lower right.
Hunt for Planetary Companions
Past radial velocity analysis suggests that giant planets of one tenth to 10 times the mass of Jupiter do not exist within 0.1 to four AUs of Star A (Cummings et al, 1999). Astronomers would find it very difficult to detect Earth-type planets around these stars using present methods.
The following star systems are located within 10 ly of BD-05 1844.
|Star System||Spectra &|
|L 961-1 AB||M V |
|L 745-46 AB||DZQ6 /VII |
|G 99-47||DA9 /VII||8.9|
|G 99-44||DZ9 /VII||9.8|
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, and the Nearby Stars Database. Additional information may be available at Roger Wilcox's Internet Stellar Database.
Although this constellation may have been named for the Unicorn prior to the 17th century, its first known historical reference is in Jakob Bartsch's star chart of 1624 as "Unicornu." Bartsch, the son-in-law of Johannes Kepler, is believed to have relied on earlier works that have never been identified. For more information about the stars and objects in this constellation, go to Christine Kronberg's Monoceros. For an illustration, see David Haworth's Monoceros.
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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