What are the physical properties neutron stars, and how does theory predict these properties? ...

Answer to q. 1

Neutron stars have hot surfaces, spin rapidly, and have strong magnetic fields. Neutron stars also radiate most of their energy in the form of X-rays and gamma rays, but do not have a high luminosity.

Theory states that as gas particles fall inward, they transfer their gravitational energy to thermal energy resulting in a hot surface. The sudden collapse of the core of a massive star to the size of a neutron star should also heat the surface to about a trillion degrees.

The principle of conservation of angular momentum predicts that neutron stars will spin rapidly. All stars rotate because they form from swirling clouds of interstellar matter. As the star collapses, it must rotate faster to conserve angular momentum.

It is predicted that a neutron star should have a powerful magnetic field. The gas of a star is ionized, so the magnetic field of the star cannot move easily relative to the gas. When the star collapses, the magnetic field is squeezed into a smaller volume. This increases the strength of the magnetic field by as much as a billion times.

The surface of a neutron star is a very hot blackbody, so it is predicted that the surface will radiate in high-energy wavelength bands  X-ray and gamma ray.

Lastly, the surface is small, so the total luminosity is not great.

Answer to q. 2

TRUE

Answer to q. 3

Gamma ray bursts are observed in every direction in the Universe. If the effect came from our own galaxy, they would occur more often in the region of the Milky Way in which there are a great density of stars.

Answer to q. 4

TRUE

Answer to q. 5

The escape velocity of a celestial object is the speed that an object on its surface needs to escape the gravitational field. A black hole is so dense that the escape velocity is greater than the speed of light, so light cannot escape the black hole; hence, the term black.

Answer to q. 6

It became known as the Copernican Revolution because it was not just the adoption of a new idea but a total change in the way astronomers, and, in fact, all of humanity, thought about Earth and its place in the Universe. In fact, our modern use of the words revolution and revolutionary to describe philosophical, political, and social upheavals comes from the title of Copernicus's book, De Revolutionibus, which means On Revolutions.

Answer to q. 7

According to Einstein's theory of general relativity, compact objects in a binary system will radiate energy in the form of gravitational waves. This energy will cause the orbital radius to decrease, and the orbiting objects to get closer together.

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