Alpha Herculis

Starbox begin
name=Alpha Herculis A/BStarbox observe
epoch=J2000
ra=RA|17|14|38.80
dec=DEC| +14|23|25.0
appmag_v=3.48 / 5.4
constell=Hercules Starbox character
class=M5IIver / (G5III+F2V)
b-v=1.44
u-b=
variable=Semiregular Starbox astrometry
prop_mo_ra=-6.71
prop_mo_dec=32.78
parallax=8.53
p_error=2.03 Starbox catalog
names=α Hercules, 64 Hercules, HR 6406, HD 156014, SAO 102680. Starbox reference
Simbad=HD+156014

Alpha Herculis (α Her / α Herculis) is a multiple star in the constellation Hercules. It also has the traditional name Ras Algethi or Rasalgethi (Arabic: رأس الجاثي ra's al-jaθiyy Head of the Kneeler), and the Flamsteed designation 64 Herculis.

When viewed through a telescope, this system is resolved into two components designated α¹ and α². These two components are more than 500 astronomical units apart, with an estimated orbital period of approximately 3600 years. α¹ is a relatively massive red bright giant. α² is actually a double star system with a primary yellow giant star and a secondary, yellow-white dwarf star. (These components are sometimes designated α Herculis A, Ba and Bb, respectively.)

The angular diameter of the red giant α¹ has been measured with an interferometer as34 ± 0.8 milli-arcseconds, or 0.034 arcseconds. [cite journal | author=Benson, J. A.; Dyck, H. M.; Mason, W. L.; Howell, R. R.; Ridgway, S. T.; Dixon, D. J. | title=The infrared angular diameter of Alpha Herculis measured with a Michelson interferometer | journal=Astronomical Journal | year=1991 | volume=102 | pages=2091–2097 | doi= 10.1086/116033 | accessdate=2007-03-08 ] At an estimated distance of 120 parsecs, this corresponds to a radius of about 300 million kilometers (or 188 million miles), [cite web | last = Kaler | first = Jim | url = http://www.astro.uiuc.edu/~kaler/sow/rasalgethi.html | title = Rasalgethi | publisher = University of Illinois | accessdate = 2007-03-07 ] or 400 times the size of the Sun. It has a total of about 14 solar masses, [cite book | first=D. | last=Hoffleit | year=1982 | title=The Bright Star Catalogue | edition=4th Revised Edition | publisher=Yale University Observatory | url=http://www.maa.agleia.de/Cat/Vol1/BSC4/remarks.dat | accessdate = 2007-03-07 —See note 6406.] and has emitted a sparse, gaseous envelope that extends at least 90 astronomical units. [cite journal | last = Deutsch | first = Armin J. | title=The Circumstellar Envelope of Alpha Herculis. | journal=Astrophysical Journal | year=1956 | volume=123 | pages=210–227 | url=http://adsabs.harvard.edu/abs/1956ApJ...123..210D | accessdate=2007-02-04 | doi=10.1086/146152 ]

The star is located at the bottom of the constellation. The traditional name "Head" comes from the fact that in the antiquity Hercules was depicted upside down on the constellation maps.

References

ee also

*List of largest known stars

External links

* [http://www.alcyone.de/SIT/doubles/SIT003934.htm Alcyone entry] (Retrieved 2 February 2007)