The Astrophysics Spectator



Interactive Pages


Other Pages



Contact Information

TAS Icon Send e-mail to the editor.

RSS Channel

TAS Icon The Astrophysics Spectator Channel

In Association with

Issue 5.07

The Astrophysics Spectator

April 18, 2008

Multiple-star systems are more common than single stars in our Galactic disk.  These systems, most of which are binary systems, are comparable in size to our Solar System.  Even among very young stars, membership in a binary system is the rule.

This last fact hints that the creation of binary stars is tied to the birth of stars themselves.  How binary stars are created, however, has yet to be resolved despite over a century of serious investigation.  In fact, one theory that has persisted since the end of the 19th century—a rapidly-rotating star splits into two stars that are gravitationally bound together—has been neither established nor eliminated through theoretical investigations.  The difficulty of simulating on a computer the birth of a binary system under any theory demonstrates how difficult problems in astrophysics are to solve.

The invulnerability of this problem to solution is a nice warning to astrophysicists who look for simple speculative explanations for complex phenomena.  New physics is seductive as an explanation for many of the difficult problems of astrophysics (in solving the disparity between the gravitational mass and the luminous mass of a galaxy by invoking undetected fundamental particles, for example), but often the answer involves mundane physics that is difficult to simulate on a computer.

With this issue of the web site, I add a page to the “Stars” topical path that describes the principal theories of binary-star formation.

Next Issue:  The next issue of The Astrophysics Spectator is scheduled for April 30.

Jim Brainerd


Theories for the Birth of Binary Stars.  Theories of stellar birth must explain why most stars are in orbit with nearby companion stars.  Four theories have received considerable attention: the capture of a star by another star, the breakup of a rapidly-spinning star into two stars, the creation of a companion star from an accretion disk orbiting a star, and the fragmentation of a collapsed molecular cloud into two stars.  The last two are currently the most favored theories.  (continue)

Ad image for The Astrophysics Spectator.