When the orbital inclination i is sufficiently clone do 90″, we can nee the two components of a binary system eclipse each other. The graph of the apparent magnitude of the binary system against time is known as the LIGHT CURVE. In general the light curve of an eclipsing binary star displays two dips, or […]

Many stars t hat appear as a single pinpoint of light in the sky, when examined by means of a spectroscope produce a spectrum which appears to be the combination of the spectra from two separate stars. If the relative positions of features on the two spectra remain unaltered, the stars are known as a […]

If a binary system is close enough to us, we can see each component as a separate point of light, each of which moves round the other in a regular manner. At each point in time we can plot the positions of each star in the sky. In time each star traces out a spiral […]

When we have made observations of a binary system of stars, we wish to be able to deduce a set of numbers that describe completely the orbit of the stars in time and space. This set of parameters is known as the ORBITAL ELEMENTS of the binary system. As we shall see, it is not […]

Consider two stars orbiting around each other in space Of course the binary system itself orbits around the centre of our Galaxy, and so in general the paths along which the two stars move are inter¬twining spirals threading their way among the other stars. For simplicity, suppose that we are travelling through space with the […]

From the spectrum of a single star we can obtain an estimate of its surface temperature and also, from the width of the spectral lines, a crude estimate of the surface gravity. If we know the distance to the star, we can deduce its luminosity from its apparent magnitude and hence, by applying Stefan’s Radiation […]

Our Sun is a single star with a system of planets and other cold bodies as travelling companions. If we look around the sky we notice that some stars appear to be quite close to each other. For example, in the constellation Ursa Majoris the star £ Ursae Majoris (Mizar) has a fainter star 80 […]