CD-42 5678 / Gl 370 / HD 85512

CD-42 5678 is also listed as HD 85512 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. Some astronomers may also refer to this star by its designation as Gliese or Gl 370 in the famous Gliese Catalogue of Nearby Stars (CNS, now ARICNS database) of Wilhelm Gliese (1915-93), who was a longtime astronomer at the Astronomiches Rechen-Institut at Heidelberg (even when it was located at Berlin). (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.)

HD 85512 or Gl 370, however, was probably first catalogued as CD-42 5678, 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.

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	Orbital Distance (a=AUs)	Orbital Period (P=years)	Orbital Eccentricity (e)	Orbital Inclination (i=degrees)	Mass (Earths)	Diameter (Earths)	Density (Earths)	Surface Gravity (Earths)	Metallicity (Solar)
HD 85512	0.0	...	...	...	230,000	83	...	...	0.47
Inner H.Z. Edge?	0.295	0.184	0.0	...	...	...	...	...	...
Planet b	0.26	0.160	0.11	?	~3.6	>1	...	...	...
Outer H.Z. Edge?	0.591	0.521	0.0	...	...	...	...	...	...

HD 85512

HD 85512 is an orange-red main-sequence dwarf star of spectral and luminosity type K5 V. The star may have 69 percent of Sol's mass (Pepe et al, 2011; and Kaltenegger et al, 2011, Table 1), around 76 percent of its diameter (NASA Stars and Exoplanet Database, derived from the power law formula of Kenneth R. Lang, 1980), and 12.6 +/- 0.8 percent of its theoretical bolometric luminosity (Pepe et al, 2011; Kaltenegger et al, 2011; and NASA Stars and Exoplanet Database; and Kenneth R. Lang, 1980). The star appears to be nearly 47 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron (Pepe et al, 2011; and Kaltenegger et al, 2011, Table 1). It may be around 5.61 +/- 0.61 billion years old (Pepe et al, 2011; and Kaltenegger et al, 2011, Table 1). Compared to our Sun, Sol, HR85512 rotates relatively slower at 47.13 +/- 6.98 days (Pepe et al, 2011; and Kaltenegger et al, 2011, Table 1). Useful catalogue numbers and designations for the star include: Gl 370, Hip 48331, HD 58812, CD-42 5678, CP(D)-42 4101 SAO 221544, LHS 2201, LTT 3617, and LPM 331.

Habitable Zone

Planet "b"

On August 17, 2011, astronomers associated with the High Accuracy Radial velocity Planet Searcher (HARPS) at the European Southern Observatory (ESO) uploaded a pre-print that revealed the discovery of a super-Earth of around 3.6 +/- 0.5 Earth-masses in a potentially habitable zone orbit around this star (ESO science release; Pepe et al, 2011; and Kaltenegger et al, 2011). The planet completes an orbit around HD 85512 in 58.43 +/- 0.13 days at an average distance of 0.26 +/- 0.005 AU in an mildly elliptical orbit with an eccentricity e = 0.11 +/- 0.10 (Pepe et al, 2011; and Kaltenegger et al, 2011, Table 1). This orbits places the planet near the inner edge of its host star's habitable zone, where liquid water could exist in liquid form under favorable conditions such as an albedo of 0.52 with an orbital eccentricity of 0.11 and more than 52 percent cloud cover under a sufficiently dense atmosphere of water, carbon dioxide, and molecular nitrogen like Earth's (Kaltenegger et al, 2011).

© ESO



Larger animation still.



Like Gliese 581 d, HD 85512 orbits just
within its host star's habitable zone and so
may have liquid surface water on its surface
under favorable atmospheric conditions.