HD 23079 / CD-53 738

NASA

HD 23079 is a yellowish star
brighter than our Sun, Sol.
(See a Digitized Sky Survey
image of HD 23079 at the late
John Whatmough's web site,
"Extrasolar Visions.")

System Summary

HD 23079 is located around 113 light-years from Sol (HIPPARCOS Plx=28.90, e_Plx=0.56 mas), in the northeastern part (3:39:43.1-52:54:57.0, ICRS 2000.0) of Constellation Horologium, the Pendulum Clock (near the northwestern part of Constellation Reticulum, the Net or Reticle) -- southwest of Alpha and Delta Horologii, northeast of Beta Horologii, east of Alpha Doradus, northwest of Alpha and Beta Reticuli, southeast of Phi and Chi Eridani, and southeast of Acamar (Theta1 Eridani). It is so far away that Humans cannot see the star from Earth without binoculars or a telescope. (Note - While HD 23079 is not included in the Bright Star Map available on-line, it is available as "CP-53 594" on the "150ly-h.zip" map file for the PC version of ChView that contains stars known to be located within 150 ly of Sol.) On October 15, 2001, astronomers announced the discovery of a Jupiter-type planet around this Sun-like star (press release and exoplanets.org -- details below). (See an animation of the planetary and potentially habitable zone orbits of the HD 23079 system, with a table of basic orbital and physical characteristics.)

The Star

HD 23079 is a yellowish dwarf star of spectral and luminosity type F8-G0 V. It has about 1.10 times Sol's mass (exoplanets.org), probably a larger diameter, and over 1.4 times its luminosity. Useful catalogue numbers and designations for this star include: Hip 17096, HD 23079, CD-53 738, CP(D)-53 594, SAO 233208, and LTT 1739.

"Planet b?"

On October 15, 2000, a team of astronomers (including Hugh R. A. Jones, R. Paul Butler, Chris G. Tinney, Geoffrey W. Marcy, Alan J. Penny, Chris McCarthy, Brad Carter, and Dimitri Pourbaix) announced the discovery of a giant planet around this Sun-like star (press release and exoplanets.org). Radial velocity measurements suggest that HD 23079 has a companion "b" with at least 2.54 times Jupiter's mass. It moves around HD 23079 at an average distance of 1.48 AUs (a semi-major axis just inside the orbital distance of Mars) in a highly circular orbit (e=0.06) that takes about 627.5 days (or less than two years) to complete (exoplanets.org). (See an animation of the planetary and potentially habitable zone orbits of the HD 23079 system, with a table of basic orbital and physical characteristics.)

NASA

Cassini-Huygens Mission
to Saturn and Titan

Larger image.

Planet b is probably a gas giant
and more than twice as massive as
Jupiter (shown here with Europa).

The orbit of an Earth-like planet (with liquid water) around HD 23079 may be centered around 1.2 AUs -- within the orbital distance of Mars in the Solar System -- with an orbital period around 459 days (or one and a quarter of an Earth years). However, the orbit of planet b with an average distance of 1.48 AUs would disrupt the orbital stability of an Earth-type planet in HD 23079's water zone. Astronomers would find it very difficult to detect an Earth-type planet in the water zone of this star using present methods.

Closest Neighbors

The following table includes all star systems known to be located within 10 light-years (ly), plus more bright stars within 10 to 20 ly, of HD 23079.

Star System	Spectra & Luminosity	Distance (light-years)
CP(D)-52 388 AB / HD 20916	K0 V ?	6.7
CP(D)-51 443 / CD-51 887	G1 V	8.2
CP(D)-52 497 / CD-52 858 AB	K1 Vp ?	8.4
* plus bright stars *		. . .
CD-58 689	G8 V	13
CP-47 332 / CD-47 990	G0 V	18
HR 1418	F5-8 V	20

Other Information

The late John Whatmough created illustrated web pages on this system in Extrasolar Visions.

Up-to-date technical summaries on these stars can be found at: Jean Schneiders's Extrasolar Planets Encyclopaedia; the HIPPARCOS Catalogue using the VizieR Search Service mirrored from the Centre de Données astronomiques de Strasbourg (CDS); NASA's ADS Abstract Service for the Astrophysics Data System; and the SIMBAD Astronomical Database mirrored from CDS, which may require an account to access.

Constellation Horologium, the Pendulum Clock, is one of those obscure constellations in the Southern Hemisphere invented in the mid-1880s by the Abbé [Abbot] Nicholas Louis de La Caille (1713-1762), who had the great honor of naming 15 of the 88 constellations by becoming the first astronomer to systematically observe the entire night sky. For more information about the stars and objects in this constellation, go to Christine Kronberg's Horologium. For an illustration, see David Haworth's Horologium.

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