Chapter 19 - Stars Flashcards
What are the requirements for something to be described as a planet?
-Orbits a star.
-Large enough mass to give it a round shape.
-No fusion reactions.
-Orbit cleared of most other objects.
Define planetary satellite.
A body in orbit around a planet.
Define comet.
A small irregular body made up of ice, dust & small pieces of rock, with an eccentric elliptical orbit.
Define solar system.
A system made of a star and the satellites that orbit it.
Define galaxy.
A collection of stars and interstellar dust & gas.
Define universe.
Everything that exists within space and time.
Outline the formation of a star.
-Dust & gas particles gravitate together into a protostar.
-Gravity becomes strong enough for nuclear fusion.
-Main sequence star, where gravity = radiation pressure.
How does a low-mass main sequence star form a red giant?
-Hydrogen in core runs low.
-Star begins to collapse as gravity > radiation pressure.
-Pressure becomes high enough for fusion in the shell around the core, causing expansion.
-Electron degeneracy pressure stops the core getting any smaller.
How does a red giant form into a white dwarf?
-The outer layers drift into space, forming a planetary nebula.
-The core is left behind.
What is electron degeneracy pressure?
A pressure created by the electrons in the core of a collapsing star.
What is the Chandrasekhar limit?
The maximum mass a star can have at which electron degeneracy pressure prevents it from collapsing.
Define planetary nebula.
The outer layers of a red giant that have drifted off into space.
What are the characteristics of a white dwarf?
-No fusion occurs.
-Leaks photons made earlier in its lifecycle.
-Hot & dense.
How does a high-mass main sequence star form a red supergiant?
-Hydrogen is used up quicker.
-Helium in the core fuses into heavier elements, causing expansion.
How does a red supergiant go supernova?
-When fuel runs out, the core contracts.
-Outer layers fall in and rebound, causing a supernova.
-Either a neutron star or a black hole is left.
