BD-05 1844 / Gl 250 AB

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).

BD-05 1844 A

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.

BD-05 1844 B

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.

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.