HR 7162 / HD 176051 AB

JPL, CalTech, NASA



Larger image from the surface of a
a hypothetical terrestrial planet
orbiting close-binary stars.



A Jupiter-class planet has been
discovered in orbit around one of
the stars in the HR 7162 AB,
close-binary star system (more).

Today, some astronomers prefer to refer to Star A as HD 176051, as it is listed 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. As a relatively bright star in Earth's night sky, however, Star A is also catalogued as Harvard Revised (HR) 7162, a numbering system derived from the 1908 Revised Harvard Photometry catalogue of stars visible to many Humans with the naked eye. The HR system has been preserved through its successor, the Yale Bright Star Catalogue -- revised and expanded through the hard work of E. Dorrit Hoffleit (1907-2007) and others.

Star A also has an older designation as BD+32 3267 from 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).

The duplicity of this star may have been first noted by Sherburne Wesley Burnham (1838-1921), who numbered it as the 648th record in his double star catalogue (BU) called "A General Catalogue of Double Stars Within 121° of the North Pole," which was published in two parts by the Carnegie Institution of Washington in 1906 and is now known as the Burnham Double Star Catalogue (BDS). Star A has a dimmer spectroscopic companion, which is less massive and more orange, and so their combined visual luminosity is nearly 1.6 that of Sol's. Their orbits around each other take just about 61.4 years to complete, with a semi-major axis of 19.1 AUs, an eccentricity of 0.2667, and an inclination of 114.2 degrees from Earth's line of sight (Muterspaugh et al, 2010, Table 1 and Table 4, pages 1659 and 1661; and Pourbaix et al, 2004; and Duquennoy and Mayor, 1991).

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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)
AB Mass Center	0.0	...	...	...	...	...	...	...	...
HR 7162 A	7.6	61.4	0.2667	114.2	353,000	~120	...	...	0.78
Inner H.Z. A	1.0	0.97	0	115.8	...	...	...	...	...
Outer H.Z. A	1.9	2.57	0	115.8	...	...	...	...	...
Inrakluk Ab?	2.02	2.8	0?	115.8	~720	~11	...	...	...
HR 7162 B	11.5	61.4	0.2667	114.2	234,000	~88	...	...	0.78
Center H.Z. B	0.57	0.49	0	115.8	...	...	...	...	...
Outer H.Z. B	1.1	1.4	0	115.8	...	...	...	...	...
Inrakluk Bb?	1.76	2.8	0?	115.8	~480	~11	...	...	...

HR 7162 A

This is a yellowish main sequence dwarf star of spectral and luminosity type F9-G0 V, with 1.07 to nearly 1.2 times Sol's mass (Muterspaugh et al, 2010, Table 1, page 1659); NASA Star and Exoplanet Database; and David F. Gray, 1992), close to 1.1 times of its diameter (Pasinetti-Fracassini et al, 2001; Johnson and Wright, 1983; and S. Leone, 1973), and nearly 1.4 times its bolometric luminosity (Muterspaugh et al, 2010, Table 1, page 1659); NASA Star and Exoplanet Database; David F. Gray, 1992; and Kenneth R. Lang, 1980). The star appears to be less enriched in elements heavier than hydrogen and helium ("metals") because it has only 78 percent of Sol's abundance of iron (Luck and Heiter, 2006, Table 3, page 3076). Based on chromospheric analysis, it appears to be around 3.8 billion years old (Don C. Barry, 1978), but an estimate derived from gyrochronology suggests around 2.4 billion years (Sydney A. Barnes, 2007, Table 6, page 32), while another study used theoretical, stellar evolutionary tracks and isochrones to estimate an age of 8.1 billion years (Holmberg et al, 2006). Useful catalogue numbers and designations for the star include: Inrakluk, HR 7162, Gl 728, Hip 93017, HD 176051, BD+32 3267, SAO 67612, LTT 15567, BU 648 A, and ADS 11871 A.

According to one type of model used in calculations for the NASA Star and Exoplanet Database, the habitable zone orbits of an Earth-like planet (with liquid water) around HR 7162 A may range between 1.0 to 1.9 AUs -- between the orbital distances of Earth and the Main Asteroid Belt in the Solar System. Assuming that the mass of Star A is 1.07 Solar-masses, then such orbital periods could range from around 353 days (0.967 year) to 937 days (2.57 years). (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)

HR 7162 B

A orange-red main sequence dwarf star of spectral and luminosity type K1 V, Star B has around 0.71 percent of Sol's mass (Muterspaugh et al, 2010, Table 1, page 1659), 81 percent of Sol's diameter (Pasinetti-Fracassini et al, 2001; and Johnson and Wright, 1983), and than than Solar luminosity. Useful catalogue numbers and designations for the star include: HR 7162 B, Gl 728 B, HD 176051 B, BD+32 3267 B, BU 648 B, and ADS 11871 B.

© Torben Krogh & Mogens Winther,



(Amtsgymnasiet and EUC Syd Gallery,
student photo used with permission)




Star B is an orange-red dwarf
star, like Epsilon Eridani
at left center of meteor.

Using Omicron Eridani A as a proxy for Star B, the habitable zone orbits of an Earth-like planet (with liquid water) around HR 7162 B can range between 0.6 to 1.1 AUs -- between the orbital distances of Venus and Mars in the Solar System. Assuming that the mass of Star B is 0.71 Solar-masses, then such orbital periods could range from around 180 days, or 0.49 year, to 502 days, or 1.4 years. (See an animation of the planetary and potentially habitable zone orbits of this system, with a table of basic orbital and physical characteristics.)

Planet "Inrakluk Ab or Bb"

Alan P. Boss, DTM,
Carnegie Institution



Larger computer image.



Disk instability can lead to the
rapid formation of spiral arms and
collapse of gas clumps into giant
planets (more).

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