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Sheliak (Beta Lyrae) in the Lyra the Harp - DSI II Color Camera
The southwestern-most
star of the parallelogram that makes the body of the Harp, Lyra's Beta star. The name Sheliak
derives from an Arabic word that refers to the celestial harp of Orpheus. The three dimmer stars surrounding the brighter Sheliak are single stars in the Tycho catalog ranging from magnitudes of 7 to 10.
Located nearly 900 light years
away, Sheliak radiates the visible light of 2000 Suns.
However, it is not one star, but two, a bright bluish hotter one orbiting a dimmer
white cooler one. The plane of the orbit
is oriented so that during an orbital period of 12.9 days each star
gets in the way of the other, with the combined light of the system at
minimum alternating between 30% and half of normal every 6.5 days.
The two stars, both quite massive, are
very close together. Tidal forces both distort the stars and cause
streams of matter to flow from one star to the other.
Beta Lyrae is the prototype of this class of eclipsing binaries, the
Beta Lyrae Stars or EB variables.
According to Dr. Jim Kaler at the University of Illinois, "such 'mass transfer' is
profoundly important in the lives of double stars and produces some
of the more bizarre of celestial phenomena (including Sheliak!).
In extreme cases, one star can actually orbit inside the extended
envelope of an expanding, dying giant star, gradually bringing the
two closer together and setting the stage for later stellar
explosions. Others are so close they actually touch at their
surfaces."
Sheliak was found to be a radio star by radio astronomers Wade and Hjellming in
1971 - another indication of the matter transfer between the two stars.
Astrophysicists think that matter is flowing from the larger to the smaller
star at 300 km/s.
(credit - SEDS)
Sheliak, a not so run-of-the-mill double star system...
Equipment: Meade LX90 8"SCT@f/10, Meade DSI II Color Camera, Baadar IR/UV cut filter.
Guiding: AT80ED 80mm APO, Meade DSI II Pro camera
100 x 4s, gain=100, offset=50
Image captured and guiding performed with Meade Envisage software. Setting black-point, color balancing and slight brightening performed in Adobe Photoshop CS.
This image was created with the help of the ESA/ESO/NASA Photoshop FITS Liberator.
August 8, 2010
Watauga Skies Observatory
Watauga, Texas
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