One of the observed systems of particular interest is 44i Bootis, a W Ursae Majoris type binary, in the consellation Boötes. The eclipsing pair consists of two G2 stars, similar in yellow color, mass, physical size, temperature, and luminosity, to our sun, which is on the main sequence of the Hertzsprung-Russell diagram. 44i Bootis is a particularily useful binary system because of its short orbital period, which is on the order of 6 and a half hours (approximately 6.43 hours, or 6 hours and 25 minutes). This means there is a primary eclipse about four times every earth day and secondary eclipses nearly halfway between every primary minimum; in other words, the stars of 44i Bootis eclipse each other almost eight times for every single time the earth turns on its axis. Since the pair are orbiting each other so quickly, the stars cannot be too far apart, and under the assumption that they retain their spherical shapes, it would seem the couple must be touching as they spin about each other. However, it has been concluded that when stars are indeed in such close proximity that they are in contact, the tidal forces between the stars distort their otherwise spherical shapes. In such close binary systems, there is a point where the gravitational attraction to each star is equal, which allows for mass transfer between the pair. Such mass exchange induces the stars to take on ellipsoidal shapes and has significant affects on the stellar evolution of the system.

Program Introduction

Created by: MelissaPereira 4/2000

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