Albireo

Starbox 2
name=SIMBAD link|HD+183912|Albireo A


caption=Albireo's position, lower right corner.
The cross-like figure is the Northern Cross.
The blue line shows the boundaries of the constellation the Swan.
epoch=J2000.0 (ICRS)
constell=Cygnus
ra_a_h=19
ra_a_m=30
ra_a_s=43.281
dec_a_d=+27
dec_a_m=57
dec_a_s=34.85
radec_a_footnote= [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/239/h_dm_com&recno=19929 HIP 95947, record for component 1] , Hipparcos catalogue; CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?I/239 I/239] .]
ra_b_h=19
ra_b_m=30
ra_b_s=43.302
dec_b_d=+27
dec_b_m=57
dec_b_s=34.61
radec_b_footnote= [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/239/h_dm_com&recno=19930 HIP 95947, record for component 2] , Hipparcos catalogue; CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?I/239 I/239] .]
prop_mo_ra_a=−7.09
prop_mo_dec_a=−5.63
prop_mo_ra_b=5.04
prop_mo_dec_b=6.48
parallax=8.46
p_error=0.58
class_a=K3IIIEntry, [http://ad.usno.navy.mil/wds/wdsnewframe4.html The Washington Double Star Catalog] , identifier 19307+2758, discoverer identifier MCA 55. Accessed on line July 9, 2008.]
class_b=B0V
parallax_footnote=SIMBAD link|HD+183912|CCDM J19307+2758A -- Double or multiple star, database entry, SIMBAD. Accessed on line July 9, 2008.]
appmag_v_a=3.18Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory, Theo ten Brummelaar, Brian D. Mason, et al., "Astronomical Journal" 119, #5 (May 2000), pp. 2403–2414. doi|10.1086/301338. bibcode|2000AJ....119.2403T. See tables 4, 5, 6, and 8. Luminosity from L_bol=10^{2(4.75−M_bol)/5}.]
appmag_v_b=5.82
v-r_a=0.92
v-r_b=0.09
absmag_v_a=−2.18
absmag_v_b=0.46
temperature_a=4080±10
temperature_b=30000±100
luminosity_bolometric_a=1200±200
luminosity_bolometric_b=950±250
mass_a=5
mass_b=3.2
radius_a=16 [ [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=II/224/cadars&recno=8926 Entry, HD 183912] , Catalogue of Stellar Diameters (CADARS); CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?II/224 II/224] .]
orbit_footnote=Entry, WDS identifier 19307+2758, [http://ad.usno.navy.mil/wds/orb6/orb6frames.html Sixth Catalog of Orbits of Visual Binary Stars] , William I. Hartkopf & Brian D. Mason, U.S. Naval Observatory. Accessed on line July 9, 2008.]
period=213.859
axis_unitless=0.536″
inclination=154.9
node=170.4
periastron=B1997.995
eccentricity=0.256
periarg=39.4
names=β Cygni A, β¹ Cygni, 6 Cygni A, MCA 55 Aac, ADS 12540 A, BD+27 3410, CCDM J19307+2758A, FK5 732, HD 183912/183913, HIP 95947, HR 7417, NSV 12105, SAO 87301, WDS 19307+2758Aa/AcSpeckle observations with PISCO in Merate: IV. Astrometric measurements of visual binaries in 2005, M. Scardia et al., "Astronomische Nachrichten" 329, #1 (2008), pp. 54–68. bibcode|2008AN....329...54S. doi|10.1002/asna.200710834.]

Albireo (β Cyg / β Cygni / Beta Cyg / Beta Cygni) is the fifth brightest star in the constellation Cygnus. Although it has the Bayer designation "beta", it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni. Albireo appears to the naked eye to be a single star but can be resolved with a telescope into a double star, consisting of a brighter yellow star (actually a binary system of two stars in orbit) and a fainter blue star. Albireo is cherished by amateur astronomers as a beautiful small telescope object.

Double star

Albireo is approximately convert|380|ly|pc|abbr=off|lk=on away from the Earth. When viewed with the naked eye, Albireo appears to be a single star. However, when viewed with a telescope it readily resolves into a double star, consisting of Albireo A (amber, apparent magnitude 3.1), and Albireo B (blue-green, apparent magnitude 5.1.) Separated by 35 seconds of arc, the two components provide one of the best contrasting double stars in the sky due to their different colors. It is not known whether the two components are orbiting around each other in a physical binary system. If they are, their orbital period is probably at least 100,000 years.p. 46, "The Monthly Sky Guide", Ian Ridpath, Wil Tirion, Cambridge University Press, 2006, ISBN 0521684358.]

Albireo A

In 1976, component A was itself discovered to be a binary star, using speckle interferometry and the 2.1-meter telescope at the Kitt Peak National Observatory. [Speckle interferometric measurements of binary stars. VI, H. A. McAlister and E. M. Hendry, "Astrophysical Journal Supplement Series" 48 (March 1982), pp. 273–278. bibcode|1982ApJS...48..273M. doi|10.1086/190778.] An orbit for the pair has since been computed using interferometric measurements, but as only approximately a quarter of the orbit has been observed, the orbital parameters must be regarded as preliminary. The current angular separation between the components of around 0.4 arcseconds is tantalizingly close to the limit which visual observations through instruments of at least 20" in size can resolve, under very rare perfect seeing conditions.

Albireo B

Starbox 1
name=SIMBAD link|HD+183914|Albireo B
epoch=J2000.0 (ICRS)
constell=Cygnus
ra=RA|19|30|45.3954SIMBAD link|HD+183914|HD 183914 -- Emission-line Star, database entry, SIMBAD. Accessed on line July 9, 2008.]
dec=DEC|+27|57|54.995
appmag_v=5.09
class=B8Ve
u-b=-0.30 [UBV observations of visual double stars, T. E. Lutz, "Publications of the Astronomical Society of the Pacific" 83 (August 1971), pp. 488–490. bibcode|1971PASP...83..488L.]
b-v=-0.06
radial_v=-18
prop_mo_ra=-1.95
prop_mo_dec=-0.98
parallax=8.67
p_error=0.65
parallax_footnote=
mass=3.3 [http://www.astro.uiuc.edu/~kaler/sow/albireo.html Albireo] , "Stars", Jim Kaler. Accessed on line July 9, 2008.]
luminosity_bolometric=230 ± 90
temperature=13200 ± 600Table 1, Physical Parameters of Southern B- and Be-Type Stars, R. S. Levenhagen and N. V. Leister, "The Astronomical Journal" 127, #2 (February 2004), pp. 1176–1180, doi|10.1086/381063, bibcode|2004AJ....127.1176L.]
radius=2.7 [ [http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-source=II/224/cadars&recno=8927 Entry, HD 183914] , Catalogue of Stellar Diameters (CADARS); CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?II/224 II/224] .]
gravity = 4.00 ± 0.15
mass = 3.7 ± 0.8
rotation=<0.6 days
age=4×10⁷ to 2×10⁸
primary=Albireo A
separation_epoch=2006
posang=54
posang_footnote=Entry, [http://ad.usno.navy.mil/wds/wdsnewframe4.html The Washington Double Star Catalog] , identifier 19307+2758, discoverer identifier STFA 43. Accessed on line July 9, 2008.]
angdistsec=35.3
angdist_footnote=
names=&beta; Cygni B, &beta;² Cygni, 6 Cygni B, STF 4043B, ADS 12540 B, BD+27 3411, CCDM J19307+2758B,
HD 183914, HIP 95951, HR 7418, SAO 87302, WDS 19307+2758B

Albireo B is a fast-rotating Be star, with an equatorial rotational velocity of at least 250 kilometers per second. [http://www.astro.uiuc.edu/~kaler/sow/albireo.html Albireo] , "Stars", Jim Kaler. Accessed on line July 9, 2008.] Its surface temperature has been spectroscopically estimated to be about 13,200 K.

Names and etymology

Since Cygnus is the swan, and Albireo is located at the head of the swan, Albireo is sometimes called the "beak star". [p. 416, "In Quest of the Universe", Theo Koupelis and Karl F. Kuhn, 5th ed., Sudbury, Massachusetts: Jones & Bartlett Publishers, 2007, ISBN 0763743879.] With Deneb, Gamma Cygni, Delta Cygni, and Epsilon Cygni, it forms the asterism called the Northern Cross. [ [http://www.daviddarling.info/encyclopedia/N/Northern_Cross.html Northern Cross] , entry, "The Internet Encyclopedia of Science", David Darling. Accessed on line July 24, 2008.]

Medieval Arabic-speaking astronomers called Albireo " _ar. minqār al-dajāja^h" (English: "the hen's beak".) [p. 196, [http://books.google.com/books?id=5xQuAAAAIAAJ "Star-names and Their Meanings"] , Richard Hinckley Allen, New York, G. E. Stechert, 1899.] Its current name is a result of misunderstanding and mistranslation. It is thought that it originated in the Greek name " _gr. ornis" for the constellation of Cygnus, which became " _ar. urnis" in Arabic. [p. 24, [http://books.google.com/books?id=9EUDAAAAQAAJ "The names of the stars and constellations compiled from the Latin, Greek and Arabic"] , W. H. Higgins, Leicester: Samuel Clarke, 1882.] When translated into Latin, this name was thought to refer to the plant "Erysimum officinale", and so was translated into a Latin name for this plant, " _la. ireo". The phrase " _la. ab ireo" was later treated as a misprint of an Arabic term and transcribed as " _ar. al-bireo". [p. 194, Allen.]

References

External links

* [http://adsabs.harvard.edu/abs/1980S&T....59..210W Albireo as a Triple Star]
* [http://antwrp.gsfc.nasa.gov/apod/ap050830.html Photo by Richard Yandrick; August 30, 2005]
* [http://www.photomeeting.de/astromeeting/double/050728betCYGa1024.htm A picture of Albireo by Stefan Seip]
* [http://www.nightskyinfo.com/archive/albireo NightSkyInfo.com - Albireo]
* [http://www.alcyone-software.com/cgi-bin/search.pl?object=HR7417 Albireo] at Alcyone Software's Star Data Pages