Beta Lyrae (β Lyr, β Lyrae) is a binary star system approximately 960 light-years (290 parsecs) away in the constellation Lyra. Beta Lyrae has the traditional name Sheliak (occasionally Shelyak), from الشلياق šiliyāq, the Arabic name of the constellation Lyra.
Beta Lyrae is a semidetached binary system made up of a stellar class B7II primary star and a secondary that is probably also a B-type star. The brighter, less massive star (B7II) in the system was once the more massive member of the pair, which caused it to evolve away from the main sequence first and become a giant star. Because the pair are in a close orbit, as this star expanded into a giant it filled its Roche lobe and transferred most of its mass over to its companion. The secondary, now more massive star is surrounded by an accretion disk from this mass transfer, with bipolar, jet-like features projecting perpendicular to the disk. This accretion disk blocks our view of the secondary star, lowering its apparent luminosity and making it difficult for astronomers to pinpoint what its stellar type is. The amount of mass being transferred between the two stars is about 2 × 10–5 solar masses per year, or the equivalent of the Sun's mass every 50,000 years, which results in an increase in orbital period of about 19 seconds each year.
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In Space Opera
- As the real world location of CY Aquarii is estimated at about 1300 light-years from Sol, far outside the "bubble" of Known Space it is suggested that the planet Gummidgy probably is in the Beta Lyrae system and not in the CY Aquarii system. The problem with that is the fact that Beta Lyrae is the location of other planets in the Known Space Universe.
- The Soft Weapon (1967), Known Space short story by Larry Niven published in the collection Neutron Star (1968). Two humans and their Puppeteer companion are ambushed on the planet Cue Ball of the Beta Lyrae system by Kzin pirates. They possess a "soft weapon" that was originally made for Thrint Slavers by the Tnuctip race, and which can morph into several forms. Taking advantage of this, the trio trick the Kzinti and escape with the weapon.
- The Slaver Weapon? (1973), episode of Star Trek: The Animated Series? written by Larry Niven, as part of the film, television, and print franchise originated by Gene Roddenberry?. In this version of the Slaver story set on an ice planet orbiting Beta Lyrae, the trio of spacefarers comprises Mr. Spock, Uhura, and Sulu. The Tnuctip? weapon self-destructs and kills the Kzin pirates.
- Frontier: Elite II? (1993) and Frontier: First Encounters? (1995), computer games written by David Braben? et al. Beta Lyrae has an unusual property: If the system is entered, the game crashes as a result of its computer code being unable to handle the mechanics of a contact binary. Only advanced players can observe this, since Beta Lyrae is so distant from the core systems that only very powerful ships can get there.