page_title: Beta Lyrae
section_title: Properties
hierarchical_section_title: Beta Lyrae / Properties
caption_attribution_description: English: Beta Lyrae is an interacting and eclipsing binary where material is gravitationally pulled away from one star and accretes on to the surface of the companion. The system has an orbital period of 13 days. Using the CHARA Array, researchers obtained images of beta Lyrae showing the mass donor and the thick disk surrounding the mass gainer. The donor is brighter and appears elongated; this is the first direct detection of photospheric tidal distortion due to Roche lobe filling. The disk component is fainter and more elongated than the donor. Reference: Zhao et al. 2008, ApJ, 684, 95
context_page_description: Beta Lyrae is a multiple star system in the constellation of Lyra. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 960 light-years distant from the Sun.
  Although it appears as a single point of light to the naked eye, it actually consists of six components of apparent magnitude 14.3 or brighter. The brightest component, designated Beta Lyrae A, is itself a triple star system, consisting of an eclipsing binary pair and a single star. The binary pair's two components are designated Beta Lyrae Aa1 and Aa2. The additional five components, designated Beta Lyrae B, C, D, E, and F, are currently considered to be single stars.
context_section_description: Beta Lyrae Aa is a semidetached binary system made up of a stellar class B6-8 primary star and a secondary that is probably also a B-type star. The fainter, less massive star 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 humans' 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.  The spectrum of Beta Lyrae shows emission lines produced by the accretion disc.  The disc produces around 20% of the brightness of the system.
caption: Beta Lyrae resolved using the CHARA array