CD-49 13515 / Gl 832

Although the star is now commonly referred by some astronomers as GJ 832 or Gliese (or Gl) 832, it was probably first catalogued as CD-49 13515, in a visual survey of southern stars begun in 1892 at the Astronomical Observatory of Cordoba in Argentina under the direction of its second director John M. Thome (1843-1908). Thome died before the completion of this southern sky atlas in 1914, when 578,802 stars from declination -22° to -90° were published as the Cordoba Durchmusterung ("Survey"). The "CD" is an extension of an older catalogue by Friedrich Wilhelm August Argelander (1799-1875) in 1863 on the position and brightness of 324,198 stars between +90° and -2° declination that were measured over 11 years from Bonn, Germany, made with his assistants Eduard Schönfeld (1828-1891) and Aldalbert Krüger (1832-1896), which became famous as the Bonner Durchmusterung ("Bonn Survey") abbreviated as BD. The BD and CD were greatly expanded and extended into the modern age of photographic surveys with the subsequent creation of the Cape Photographic Durchmusterung from South Africa.

Due to CD-49 13515's proximity to Sol, the system has been an object of high interest among astronomers. The star has been selected as a target star by NASA's optical Space Interferometry Mission (SIM). The mission will attempt to detect planets as small as three Earth-masses within two AUs of each star. (Some summary system information is available from the SIM Teams).

JPL, CalTech, NASA



Larger illustration of NASA's
Space Interferometry Mission.



Astronomers have identified
CD-46 11540 as a prime target
for NASA's optical SIM mission.

The Star

CD-49 13515 is a red dwarf star of spectral and luminosity type M1.5-3.0 V. This star has been estimated to have around 45 +/- 0.05 percent of Sol's mass (Bailey et al, 2008), 48 percent of its diameter (Pasinetti-Fracassini et al, 2001; and Johnson and Wright, 1983, page 699), and about 0.7 percent of its visual luminosity. It is chromospherically quiescent and only around 49 percent of Sol's abundance of iron relative to hydrogen (Bonfils et al, 2005a). Useful star catalogue numbers for CD-49 13515 include: Gl 832, Hip 106440, HD 204961, CP(D)-49 11439, LHS 3685, LTT 8573, LFT 1640, LPM 787, L 354-89, Sm 83, and 2MASS J21333397-4900323.

Planet "b"

On September 8, 2008, a team of astronomers (Jeremy Bailey, R. Paul Butler, G.C. Tinney, Hugh R.A. Jones, Simon O'Toole, Brad D. Carter, and Geoffrey W. Marcy) submitted a paper for publication on the discovery of a Jupiter-class planet in orbit around this dim star (Bailey et al, 2008). The planetary companion has at least 64 percent (+/- -0.06) of Jupiter's mass (or 203 Earth-masses). Moving around CD-49 13515 at an average distance (semi-major axis) of 3.4 +/- 0.4 AUs, planet b's orbit is completed within 9.4 years (3,416 +1 131 days), with an eccentricity (e= 0.12 +/- 0.11) within the Main Asteroid Belt in the Solar System.

NASA, Cassini-Huygens Mission
to Saturn and Titan


Larger image.


Planetary candidate "b"
ia massive enough to be
a gas giant like Jupiter
(shown here with Europa).

In order to be warmed sufficiently have liquid water at the surface, an Earth-type rocky planet would have to be located very close to such a cool and dim red dwarf star like CD-49 13515, somewhat farther 0.08 AU -- without accounting for infrared heating. (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)