BD+04 123 / HR 222

The star's designation of BD+04 123 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).

As a relatively bright star in Earth's night sky, Star A is catalogued as Harvard Revised (HR) 222, a numbering system derived from the 1908 Revised Harvard Photometry catalogue of stars visible to many Humans with the naked eye. The HR system has been preserved through its successor, the Yale Bright Star Catalogue -- updated and expanded through the hard work of E. Dorrit Hoffleit and others. HR 222 is also listed as HD 4628 in the Henry Draper (1837-82) Catalogue with extension (HDE), a massive photographic stellar spectrum survey carried out by Annie Jump Cannon (1863-1941) and Edward Charles Pickering (1846-1919) from 1911 to 1915 under the sponsorship of a memorial fund created by Henry's wife, Anna Mary Palmer. (More discussion on star names and catalogue numbers is available from Alan MacRobert at Sky and Telescope and from Professor James B. Kaler's Star Names.)

The Star

BD+04 123 is a main-sequence orange-red dwarf star of spectral and luminosity type K1-2 Ve. It may have around 83 percent of Sol's mass, 80 percent of its diameter (Johnson and Wright, 1983, page 647), and 24 percent of its luminosity. It appears to be only 51 percent as enriched as Sol in elements heavier than hydrogen ("metals") based on its abundance of iron (Cayrel de Strobel et al, 1991, page 277). Useful star catalogue numbers for BD+04 123 include: HR 222, Gl 33, Hip 3765, HD 4628, SAO 109471, FK5 1019, LHS 121, LTT 10285, LFT 73, Hei 202, and Wolf 25.

BD+04 123 B?

According to the Astronomiches Rechen-Institut at Heidelberg's ARICNS entry for Gl 33, BD+04 123 was once thought to have a flaring, presumably stellar companion at a separation of around 20 AUs (2.69" at 340.7° in 71.62 to 270" at 353.2° in 78.69), but Hei 202 was not be found in the reference cited (Wulff Dieter Heintz, 1985). Subsequent studies failed to resolve a companion star, both by speckle interferometry (Hartkopf and McAlister, 1983) and by radial velocity analysis (Marcy and Benitz, 1989).

Hunt for Substellar Companions

Using the radial velocity technique pioneered by Geoffrey W. Marcy and R. Paul Butler, the Lick Planet Search for substellar companions has thus far failed to find a brown dwarf or large Jupiter- or Saturn-mass object in a "torch" orbit around BD+04 123 (Cumming et al, 1999). On the other hand, the distance from BD+04 123 where an Earth-type planet would be "comfortable" with liquid water is centered around only 0.49 AU -- between the orbital distances of Mercury and Venus in the Solar System -- where a planet probably would have an orbital period around 137 days or more than a third of an Earth year. At such a close distance to BD+04 123, astronomers would have great difficulty in detecting such a planet using present methods.