CD-27 3124 / HD 47186

Today, many astronomers refer to this star as HD 47186, as designated in the Henry Draper (1837-82) Catalogue with subsequent 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. However, it was probably first designated as CD-27 3124 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.

The Star

HD 47186 is a main-sequence dwarf star of spectral and luminosity type G5-6 V. The star probably has a mass slightly smaller than Sol's, a smaller diameter, and around 90 percent of Sol's visual luminosity. It appears to be 1.5 times as enriched as Sol in iron relative to the abundance of hydrogen and nearly 105 percent as enriched as Sol in elements other than hydrogen, helium, and iron (Gray et al, 2006; and Nordström et al, 2004). Useful catalogue numbers and designations for the star include: Hip 31540, HD 47186, CD-27 3124, CPD-27 1377, SAO 172008, LTT 2597, and 2MASS J06360878-2737200.

Planetary System

JPL, NASA



Larger image.



It is not yet known whether
Neptune-sized planetary
candidate "b" is rocky or
gaseous.

On June 16, 2008, a team of astronomers announced at the 2008 Extra Solar Super-Earths Workshop in France their discovery of Neptune-class planet in a tight orbit around this star with another Jupiter-like planet in an outer orbit (ESO press release and Bouchy et al, forthcoming 2008). Planet "b" has 22.8 Earth-masses (0.0717 Jupiter-masses) and probably a highly circular orbital with a period of only 4.08 days. Planet "c" has 35 percent of Jupiter's mass (just a little larger than Saturn) and an orbital period of 3.7 years (1,354 days).

NASA

Larger image.

Planetary candidate "c" is a little
more massive than Saturn.

The orbit of an Earth-like planet with surface water would be centered around 0.95 AU -- near the Earth's orbital distance in the Solar System. Such an orbit would take nearly a year (around 345 days) to complete. It is possible, however, that the orbit distance of the massive planetary candidate c at around 2.4 AUs could perturb the stability of an Earth-sized planet in the habitable zone. Astronomers would find it very difficult to detect an Earth-sized planet around this star using present methods. (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)