Origins AA3051 Origins AA3051 Topic A:Binary Star Topic A:Binary Star

Formation-why are there so Formation-why are there so many binaries? many binaries?

Sir William HerschellSir William Herschell

Coined the term Coined the term “binary star” to “binary star” to describe a pair of describe a pair of stars in a single stars in a single system.system.

Presented the first Presented the first observational observational evidence for evidence for existence of binary existence of binary stars.stars.

Commonality of Binary Star Commonality of Binary Star Systems.Systems.

Star surveys have found that Star surveys have found that up to 80% of F and G up to 80% of F and G spectral type stars exist in spectral type stars exist in binary or multiple star binary or multiple star systems (Heinz 1969).systems (Heinz 1969).

Duquennoy and Mayor,in Duquennoy and Mayor,in their extensive study of G their extensive study of G type stars,show that up to type stars,show that up to two thirds exist in two thirds exist in binary/multiple star binary/multiple star systems(1991). systems(1991).

Thus there is a tendency to Thus there is a tendency to assume that ALL assume that ALL stars,whatever their spectral stars,whatever their spectral type,are binaries or multiplestype,are binaries or multiples

Recent Stellar Research In Recent Stellar Research In the Last 20 Years.the Last 20 Years.

Initial mass function(IMF) has been found to Initial mass function(IMF) has been found to peak between 0.1-0.5 solar 5masses.(Kroupa peak between 0.1-0.5 solar 5masses.(Kroupa 2005)2005)

Binary star numbers has been liked to Binary star numbers has been liked to spectral type.spectral type.

A “Brown dwarf desert” has been detected A “Brown dwarf desert” has been detected which suggests that Duquennoy and Mayor which suggests that Duquennoy and Mayor may have exaggerated the ‘multiplicity may have exaggerated the ‘multiplicity fraction’ of G-type stars.(Mccarthy and fraction’ of G-type stars.(Mccarthy and Zuckerman 2004,Marcy and Butler 2005).Zuckerman 2004,Marcy and Butler 2005).

Single star fraction(SSF) for M class stars Single star fraction(SSF) for M class stars may be as high as 70%.may be as high as 70%.