BD+26 2184 / HD 97658

The star is now commonly referred by some astronomers as HD 97658, as designated 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. It was probably first designated as BD+26 2184 in a catalogue that was originally published in 1863 by Friedrich Wilhelm August Argelander (1799-1875) on the position and brightness of 324,198 stars between +90° and -2° declination that were measured over 11 years from Bonn, Germany with his assistants Eduard Schönfeld (1828-1891) and Aldalbert Krüger (1832-1896). The catalogue became famous as the Bonner Durchmusterung ("Bonn Survey") and is typically abbreviated as BD. It was later expanded and extended during the early 20th Century with the Cordoba (observed from Argentina) then the Cape Photographic Durchmusterung (observed 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 97658	0.0	...	...	...	281,000	80	...	...	54-59
Planet "b"	0.083	0.026	~0	?	=>8.2	>1	...	...	...
Center of H.Z.?	0.58	0.48	0	...	...	...	...	...	...

The Star

BD+26 2184 is a main-sequence orange-red dwarf star of spectral and luminosity type K1 V -- but was classed as yellow as K0 in the Henry Draper Catalogue (NASA Star and Exoplanet Database). It may have around 85 percent of Sol's mass (Howard et al, 2010, for HD 97658 on Table 1, page 3), 73 percent of its diameter (Howard et al, 2010, for HD 97658 on Table 1, page 3), and 34 percent of its bolometric luminosity (Howard et al, 2010, for HD 97658 on Table 1, page 3; and the NASA Star and Exoplanet Database, derived from the exponential formula of Kenneth R. Lang, 1980). It appears to be 54 to 59 percent as enriched as Sol in elements heavier than hydrogen ("metals") based on its abundance of iron (Howard et al, 2010, for HD 97658 on Table 1, page 3; Raghavan et al, 2010; and Valenti and Fischer, 2005). BD+26 2184 appears to be a chromospherically inactive star (Howard et al, 2010). Useful star catalogue numbers for BD+26 2184 include: GJ 3651 (previously "not numbered" or NN 3651), Hip 54906, HD 97658, SAO 81730, and 2MASS J11143316+2542374.

Habitable Zone

Estimates provided by the NASA Star and Exoplanet Database -- where the inner edge of BD+26 2184 's habitable zone could be located at around 0.517 AUs from the star and its center around 0.764 AU, while the outer edge lies farther out at around 1.016 AUs -- appear to be somewhat high based on the star's significantly sub-Solar luminosity. Based on its bolometric luminosity (a high estimate from the NASA Star and Exoplanet Database), the distance from BD+26 2184 where an Earth-type planet would be "comfortable" with liquid water is centered around only 0.583 AU -- between the orbital distances of Mercury and Venus in the Solar System. An Earth-type in such a water-zone orbit would probably would have a period of around 176 days or just under half an Earth year.

Planet b?

JPL, NASA



Larger illustration.



Like planet e around
55 Cancri A and HD 7924 b,
HD 97658 b has a very hot,
tight orbit within 0.083 AUs.

On November 1, 2010, a team of astronomers working with the NASA-UC Eta-Earth Survey revealed the detection of a super-Earth in a torch orbit with a minimum of 8.2 +- 1.2 Earth-masses around BD+26 2184, using radial-velocity measures from the Keck Observatory's High Resolution Echelle Spectrometer (HIRES). Planet "b" completes an inner orbit around BD+26 2184 in 9.494 +/- 0.995 days at an average orbital distance of 0.0831 +/- 0.0011 AU. Its orbit is assumed to be circular, e ~ 0.0 (Howard et al, 2010, Table 3, page 4).

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