The possibility that the degeneracy pressure of neutrons might stabilize a self gravitating object was first noted in the 1930s by T. L.D. Landau and F.Zwicky. W.Baade and F.Zwicky emphasized that they might exist as the stellar remnant of a supernova explosion, interest in neutron stars was aroused by the discovery of X-ray stars in […]
A self-gravitating object which is supported by neutron-degeneracy Pressure is Known as a NEUTRON STAR; they were investigated Theoretically long before they were discovered in space. Their properties are analogous to those of white dwarfs except that their radii are smaller by a factor of about 1840 (the ratio of neutron mass to electron mass). […]
A single isolated neutron decays into a proton, an electron and anti -neutrino with a half-life of 12 minutes. This is an example of ? decay. However, in matter in which the electrons are moving at nearly the velocity of light, the reverse process can take place: an energetic electron collides with a proton to […]
In 1844. F.W.Bessel deduced from the motion of Sirius that it must have an unseen companion. This companion, Sirius B, was dis¬covered in 1862 by A.clark ; it is a tenth-magnitude object, eleven magnitudes fainter than Sirius A. and yet both components have the same surface temperature. The large difference in brightness must therefore be […]
We have seen how main-sequence stars are supported against gravitational collapse by the enormous gas pressures sustained by the fusion energy .Since fuel for the nuclear reactions runs out eventually become important .Low-mass stars that have run out of energy are eventually stabilized against collapse by the electron degeneracy pressure discussed above and they are […]
The properties of very dense matter are so peculiar that you may not be familiar with the underlying physical principles. In order to appreciate the implications for astrophysics of these principles we give here a brief outline of the behaviour of matter at high densities. Naturally the presentation involves some elementary algebra. All of the […]
As a star evolves and burns its ever-diminishing supply of nuclear fuel it becomes less and less able to support itself against the inexorable force of gravitation. The material in the centre of our Sun is only about 100 times as dense as water, but the centres of some collapsed stars in which the supplies […]
Many Wolf Rayet stars are found in close binary systems that consist of a massive, luminous, main-sequence 0 star and a less massive, smaller, yet even more luminous companion. Because it is so luminous, the small star expels the outer parts of its atmosphere in the form of a dense stellar wind, winch produces a […]
It is reasonable to assume that the two stars in a binary system formed at the same time. The chance of a collision between two single stars in the Galaxy is very small; t he chance of the capture of one by another of a different age to form a binary system smaller still. It […]
Of course, not all eclipsing binaries can be analysed in the way we have described above; often a certain amount of guess-work has to be employed. A case of particular interest is the star £ Aurigae. This is an eclipsing binary system consisting of a small, blue, bright B star with radius 5 solar radii […]