Chi Draconis 2

NASA

Chi Draconis A is a yellowish star that is
brighter than our Sun, Sol. (See a
Digitized Sky Survey image of Chi
Draconis from the Nearby Stars Database.)

System Summary

This system is located about 26.3 light-years (ly) away from our Sun, Sol. It lies in the northeastern part (18:21:03.38+72:43:58.24, ICRS 2000.0) of Constellation Draco, the Dragon -- southwest of Tyl (Epsilon Draconis) and northwest of Nodus Secundus (Delta Draconis). The system was first detected as a spectroscopic binary on October 25, 1898 by William Hammond Wright (1871-1959) -- observing under and reported by William Wallace Campbell (1862-1938) -- at Lick Observatory, who soon determined its orbit (Wright, 1900). (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.)

Chi Draconis A

This star is a main-sequence white-yellow dwarf of spectral and luminosity type F7 V. The star has about 1.03 times Sol's mass, possibly 1.2 times its diameter, and about 1.86 times its luminosity (Tomkin et al, 1987). Chi Draconis A appears to be an old disk star at perhaps eight billion years old. It appears to be less enriched than Sol in elements heavier than hydrogen ("metals") with only about 47 percent of Sol's abundance of iron (Cayrel de Strobel et al, 1991, page 31). Star A has the New Suspected Variable designation of NSV 10749. Useful star catalogue numbers for Chi Draconis A include: Chi Dra, 44 Dra, HR 6927, Gl 713 A, Hip 89937, HD 170153, BD+72 839, SAO 9087, FK5 695, LHS 3379, LTT 15438, and LFT 1413.

Previous orbital calculations (Tomkin et al, 1987; and Duquennoy and Mayor, 1991, page 9 and 22) have been slightly revised. According to new measurements (Dimitri Pourbaix, 2000) found in the new Sixth Catalog of Visual Orbits of Binary Stars, Stars A and B have an "average" separation (semi-major axis) of 0.991 AU, that varies between 0.6 and 1.4 AUs in an eccentric orbit (e= 0.414) that takes 280.5 days -- over three-quarters of an Earth year -- to complete. The inclination of their orbit is 74.8° from the perspective of an observer on Earth. Despite the closeness of the binary orbit, there appears to be significant noncoplanarity between the orbital and equatorial planes of Star A (Alan Hale, 1994, pages 18-19).

© Torben Krogh & Mogens Winther,

(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)

Chi Draconis B is an orange-red
dwarf star, like Epsilon Eridani at
left center of meteor.

Chi Draconis B

This star appears to be a main-sequence orange-red star of spectral and luminosity type K0 V. The star has about 75 percent of Sol's mass and about 29 percent of its luminosity (Tomkin et al, 1987). It appears to be less enriched than Sol in elements heavier than hydrogen ("metals") with only about 47 percent of Sol's abundance of iron (Cayrel de Strobel et al, 1991, page 31).

Hunt for Substellar Companions

According to one estimate based on the combined luminosity of this relatively close binary, the distance from Chi Draconis AB where an Earth-type planet would be "comfortable" with liquid water may be centered around 1.45 AU -- just inside the orbital distance of Mars in the Solar System. Unfortunately, this is too close for a stable orbit around both two stars.

Closest Neighbors

The following star systems are located within 10 light-years of Chi Draconis.

Star System	Spectra & Luminosity	Distance (light-years)
LP 71-165	M4.5 V	3.9
G 227-29	M V	5.0
AC+65 6955	M3 V	6.1
LP 44-113	DXP9 /VII	6.4
Sigma Draconis	G9 V	7.9
BD+61 2068 AB	M0 V M V	8.2

Other Information

Up-to-date technical summaries on these stars can be found at: the Astronomiches Rechen-Institut at Heidelberg's ARICNS, the Nearby Stars Database, and the Research Consortium on Nearby Stars (RECONS). Additional information may be available at Roger Wilcox's Internet Stellar Database.

Constellation Draco is associated with the dragon slain by Cadmus, the brother of Europa. It is a large and extended constellation of the northern hemisphere and is one of the few constellations which really resemble the object they were named after. For more information about the stars and objects in this constellation and an illustration, go to Christine Kronberg's Draco. For another illustration, see David Haworth's Draco.

For more information about stars including spectral and luminosity class codes, go to ChView's webpage on The Stars of the Milky Way.