System Algol

algol aa2 orbits algol aa1. animation assembled 55 images of chara interferometer in near-infrared h-band, sorted according orbital phase. because phases poorly covered, aa2 jumps @ points along path.



interpolation of orbit of aa2 around aa1 focus on aa1.

from point of view of earth, algol aa1 , algol aa2 form eclipsing binary because orbital plane contains line of sight earth. more precise, algol triple-star system: eclipsing binary pair separated 0.062 astronomical units (au) each other, whereas third star in system (algol ab) @ average distance of 2.69 au pair, , mutual orbital period of trio 681 earth days. total mass of system 5.8 solar masses, , mass ratios of aa1, aa2, , ab 4.5 1 2.

the 3 components of bright triple star used be, , still are, referred β per a, b, , c. washington double star catalog lists them aa1, aa2, , an, 2 faint stars b , c 1 arcmin distant. further 5 faint stars listed companions.

studies of algol led algol paradox in theory of stellar evolution: although components of binary star form @ same time, , massive stars evolve faster less massive stars, more massive component algol a still in main sequence, less massive algol b subgiant star @ later evolutionary stage. paradox can solved mass transfer: when more massive star became subgiant, filled roche lobe, , of mass transferred other star, still in main sequence. in binaries similar algol, gas flow can seen.

this system exhibits x-ray , radio wave flares. x-ray flares thought caused magnetic fields of , b components interacting mass transfer. radio-wave flares might created magnetic cycles similar of sunspots, because magnetic fields of these stars ten times stronger field of sun, these radio flares more powerful , more persistent.

magnetic activity cycles in chromospherically active secondary component induce changes in radius of gyration have been linked recurrent orbital period variations on order of Δp/p ≈ 10 via applegate mechanism. mass transfer between components small in algol system significant source of period change in other algol-type binaries.

algol 92.8 light-years sun, 7.3 million years ago passed within 9.8 light-years of solar system , apparent magnitude −2.5, considerably brighter star sirius today. because total mass of algol system 5.8 solar masses, @ closest approach might have given enough gravity perturb oort cloud of solar system , hence increase number of comets entering inner solar system. however, actual increase in net cometary collisions thought have been quite small.