wiki Word: Binary star

Definition: A binary star is 1 of the two stars in a binary star system, or stellar system, and orbit around a center of mass.

A stellar system, or star system, is a small number of stars that orbit eachother. A binary star system consists of only 2 stars, or companions. They are bound by gravitational attraction, where the center of mass, or center of gravity is the point where gravity can be said to act. A stellar system of two stars is known as a binary star, binary star system or physical double star. When there aren't tidal effects, perturbation from other forces, or transfer of mass from one star to the other, the system is stable. Both stars trace out an elliptical orbit around the center of mass.  Examples of binary star systems are Sirius, Procyon and Cygnus X-1. Sirius and Procyon look like a single star to the naked eye, but are actually a binary stars.  Sirius contains the companions Sirius A, and Sirius B. Procyon contains the companions Procyon A and Procyon B. Cygnus X-1 contains a blue supergiant, and a star so massive it is thought to be a black hole.

 LINCS

Sirius A (right), and Sirius B (lower left).                 Procyon A is a white star.

Sirius A is significantly larger.                                 It is 1.4 times the mass, twice the diameter,

                                                                               and 7.5 times more luminous than the Sun.

An artist's concept of Cygnus X-1.

It shows hot gas from the supergiant flowing toward the black hole.

An example of a binary star system, where two bodies with similar mass orbit around a common barycenter.

A barycenter is the point between two objects where they balance each other.

It is the center of gravity where two or more celestial bodies orbit each other.

SO WHAT?

We are studying this term, to help us better understand our universe. The universe is vast and complex, and by studying the many different things out there, it will increase our knowledge and understanding. To be sucessful in science, you must understand how a binary star system works. Gravity keeps the binary stars in orbit. To understand binary star systems you must understand the laws of gravity, barycenters, and how stars orbit, rotate, and revolve. Some of the most massive stars in our universe are binary stars. Binary stars help to show what a barycenter is. Our earth and moon also have a barycenter, and orbit around eachother. Scientists hope to someday travel closer to binary stars, to study them and learn how truly unique and amazing they are. Someday in the future, it may be one of us who is on that mission.

Sources~

Gebhardt, Karl. "Cygnus X-1." 2005-2006. Stardate Online.

       <http://blackholes.stardate.org/directory/factsheet.php?id=13>

Information about the Cygnus X-1 system is provided.

Kaler, Jim and Kulmann, Christoph. "Procyon 2." 1998-2007. Sol Company.

       <http://www.solstation.com/stars/procyon2.htm>

Information about the Procyon System is provided.

Pasachoff, Jay M. Ph.D. Astronomy. Boston, MA: Prentice Hall, 2005.

General information about binary stars is provided.

Wales, Jimmy and Sanger, Larry. "Binary Star." 2008, April 28. Wikipedia Online.

       <http://en.wikipedia.org/wiki/Binary_star>

General and extended information about binary stars is provided.