HR 4523 AB

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NASA

HR 4523 A is a yellow-orange star
like our Sun, Sol. (See a Digitized
Sky Survey image of HR 4523
from the Nearby Stars Database.)

System Summary

This binary system is located about 30.1 light-years (ly) away from our Sun, Sol, in the northernmost portion (11:46:31.07-40:30:01.27, ICRS 2000.0) of Constellation Centaurus, the Centaur -- northwest of Delta Centaurus and south of Beta and Zeta Hydrae. According to the Yale Bright Star Catalogue, 1991 5th Revised Edition notes entry for HR 4523, the system is a member of the 61 Cygni and/or the Epsilon Indi group. As HR 4523 A has become one of the top 100 target stars for NASA's planned Terrestrial Planet Finder (TPF), images of this star and its position relative to the Milky Way in Earth's night sky are now available from the TPF-C team.

JPL, CalTech, NASA

Larger illustration

Astronomers have identified
HR 4523 A as a prime target
for the Terrestrial Planet Finder
(TPF), now planned for launch
between 2014 and 2020.

As a relatively bright star in Earth's night sky, Star A is catalogued as Harvard Revised (HR) 4523, 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 -- revised and expanded through the hard work of E. Dorrit Hoffleit and others. HR 4523 is also listed as HD 102365 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.)

HR 4523 A

This star is a yellow-orange main sequence dwarf star of spectral and luminosity type G3-5 V, with six to eight tenths of Sol's mass (Kovacs and Foy, 1978) -- but possibly the same mass as Sol, 96 percent of its diameter, and about 82 percent of its luminosity. It appears to be metal deficient compared with Sol, as it is only 20 to 33 percent as enriched with elements heavier than hydrogen ("metallicity") based on its abundance of iron (Cayrel de Strobel et al, 1991, page 292). HR 4523 A may be substantially older than 9 billion years (Kovacs and Foy, 1978) as an old disk star (Hearnshaw, 1972).

HR 4523 A has a very dim companion. Star B has an observed separation from the primary of 194 AUs, possibly with a semi-major axis around 235 AU -- where a= 25.4" with a HIPPARCOS parallax of 0.10823 +/- 0.00070" (Poveda et al, 1994, pages 68-69). Useful star catalogue numbers for HR 4523 A include: Gl 442 A, Hip 57443, HD 102365, CD-39 7301, CP(D)-39 5265, SAO 223020, LHS 311, LTT 4373, LPM 399, and LFT 848.

HR 4523 B

This star is a very dim, red main sequence dwarf star of spectral and luminosity type M V. This star may have only seven percent of Sol's mass, 15 percent of its diameter, and about 7/100,000th of its luminosity. Useful star catalogue numbers for the star include: Gl 442 B, LHS 313, and VB 5.

NASA -- larger image

HR 4523 B is a dim red dwarf star, like Gliese
623 A (M2.5V) and B (M5.8Ve) at lower right.

Hunt for Substellar Companions

A recent 2.5-year search analyzing radial velocities failed to find a large Jupiter or brown dwarf within 10 AUs of HR 4523 A (Murdoch et al, 1993, pages 351 and 358). The distance from star A where an Earth-type planet would be "comfortable" with liquid water is centered around 0.90 AU -- about the orbital distance of Venus in the Solar System, with an orbital period about 313 days, or about 86 percent of an Earth year. For star B, the liquid water zone is centered aroud 0.0086 AU with an orbital period of only 1.1 days. Astronomers are hoping to use NASA's Terrestrial Planet Finder (TPF) and the ESA's Darwin planned groups of observatories to search for a rocky inner planet in the so-called "habitable zone" (HZ) around Kappa Ceti. As currently planned, the TPF will include two complementary observatory groups: a visible-light coronagraph to launch around 2014; and a "formation-flying" infrared interferometer to launch before 2020, while Darwin will launch a flotilla of three mid-infrared telescopes and a fourth communications hub beginning in 2015.

Closest Neighbors

The following star systems are located within 10 light-years of HR 4523 AB.

Star System	Spectra & Luminosity	Distance (light-years)
L 396-7	M3.5 V	4.3
CD-31 9113	M2 V	4.4
CD-32 8179 AB	K0 V M V	4.4
CD-51 5974	K0-M0 V-VI	6.3
L 399-68	M3.5 V	7.3
CD-26 8883 AB	K4-5 V ?	7.8
CD-51 6859	M3 V	7.9
L471-42	M4 V	8.2
Hip 50798	?	9.7

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 Centaurus cannot be viewed from middle northern latitudes of around 40 degrees, but should become more easily visible to observers that travel south of the equator. For more information about the stars and objects in this constellation and an illustration, go to Christine Kronberg's Centaurus. For another illustration, see David Haworth's Centaurus.

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