Chapter 13 Flashcards
Neutron star
An elementary particle with roughly the same mass as a proton, but which is electrically neutral. Along with protons, neutrons form the nuclei of atoms.
Pulsars
Object that emits radiation in the form of rapid pulses with a characteristic pulse period and duration. Charged particles, accelerated by the magnetic field of a rapidly rotating neutron star, flow along the magnetic field lines, producing radiation that beams outward as the star spins on its axis.
Lighthouse model
The leading explanation for pulsars. A small region of the neutron star, near one of the magnetic poles, emits a steady stream of radiation that sweeps past Earth each time the star rotates. The period of the pulses is the star’s rotation period.
X-ray bursters
X-ray source that radiates thousands of times more energy than our sun in short bursts lasting only a few seconds. A neutron star in a binary system accretes matter onto its surface until temperatures reach the level needed for hydrogen fusion to occur. The result is a sudden period of rapid nuclear burning and release of energy.
Millisecond pulsars
A pulsar whose period indicates that the neutron star is rotating nearly 1000 times each second. The most likely explanation for these rapid rotators is that the neutron star has been spun up by drawing in matter from a companion star.
Gamma-ray bursts
Object that radiates tremendous amounts of energy in the form of gamma rays, possibly due to the collision and merger of two neutron stars initially in orbit around one another.
Notes for escape speed would double
1/(√1/4) = 2
Event horizon
Imagionary spherical surface surrounding a collapsing star with radius equal to the schwarzschild radius, within which no event can be seen, heard, or known about by an outside observer.
Gravitational redshift
A prediction of Einstein’s general theory of relativity. Photons lose energy as they escape the gravitational field of a massive object. Because a photon’s energy is proportional to its frequency, a photon that loses energy suffers a decrease in frequency, which corresponds to an increase, or redshift, in wavelength.
Singularity
A point in the universe where the density of matter and gravitational field are infinite, such as at the center of a black hole.
Black hole
The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object. Also referred to as the Planck curve.
General theory of relativity
Theory proposed by Einstein to incorporate gravity into the framework of special relativity.
Schwarzschild radius
The distance from the center of an object such that, if all the mass were compressed within that region, the escape speed would equal the speed of light. Once a stellar remnant collapses within this radius, light cannot escape and the object is no longer visible.
