Rotational Motion & Astrophysics - Knowledge Flashcards
General Relativity
Deals with motion in accelerating (non-inertial) frames of reference.
Mass curves spacetime and gravity arises from the curvature of spacetime.
Equivalence Principle
It is not possible to distinguish between the effects on an observer of a uniform gravitational field and of a constant acceleration
Event horizon of a black hole
From the perspective of a distant observer, time appears to be frozen at the event horizon of a black hole
Formation of stars
Stars are formed in interstellar clouds when gravitational forces overcome thermal pressure, and cause a molecular cloud to contract until the core becomes hot enough to sustain nuclear fusion, which then provides a thermal pressure that balances the gravitational force.
The proton-proton chain
When two protons fuse together to produce deuterium, a positron and a neutrino. The deuterium now fuses together another proton to give helium-3, and releases gamma radiation. Two helium-3 nuclei fuse to form a helium-4 nucleus and releases two protons.
Hydrogen fusion in the core of stars
Hydrogen fusion in the core supplies the energy that maintains the star’s outward thermal pressure to balance inward gravitational forces. When the hydrogen in the core becomes depleted, nuclear fusion in the core ceases. The gas surrounding the core still contains hydrogen. Gravitational forces cause the core and the surrounding shell of hydrogen to shrink. The hydrogen shell becomes hot enough for hydrogen fusion in the shell of the star. This leads to an increase in pressure which pushes the surface of the star outwards, causing it to cool. At this stage, the star will be in the giant or supergiant regions of a Hertzspung-Sussel diagram.
Lifetime of a star
Every star ultimately becomes a white dwarf, a neutron star or a black hole depending on the mass of the star.
