Astrophysics Flashcards
How are nebulae formed
Over millions of years, as the tiny gravitational attraction between particles of dust and gas pulls the particles towards each other, eventually forming vast clouds, mainly hydrogen.
How are protostars formed
Gravitational collapse accelerates as dust and gas come closer together. Variations in the nebula lead to denser regions that attract more matter, increasing mass and density. This process converts gravitational energy to thermal energy, causing the region to become hotter.
How are stars formed
As mass of protostar increases due to gravitational collapse, the cores temperature increases, reaching a temperature where the kinetic energy of the hydrogen nuclei is large enough to overcome the electrostatic repulsion. Hydrogen nuclei fuse to make helium nuclei as nuclear fusion begins. A star is born. The radiation pressure from photons emitted due to fusion, and gas pressure from the nuclei in the core create an outward force, equalling the force of gravitational collapse, maintaining equilibrium and staying stable. Star is in its main sequence
What is a planetary satellite
An object orbiting a planet.
What happens during the death of a star between 0.5M and 10M
Runs out of hydrogen to fuse. Gravitational force greater than reduced radiation and gas pressure, core begins to collapse. Fusion occurs in shell around core, no longer in core. Gas and radiation pressure from fusion in shell cause outer layers of Red Giant to expand and move away from core, eventually forming a planetary nebula. Core is left behind as a white dwarf.
Electron degeneracy pressure.
If core has mass less than 1.44M, electron degeneracy pressure prevents the core from further collapse. 1.44M is the Chandrasekhar limit.
What happens during the death of a star greater than 10M
Cores in Massive suns have a much higher temperature, so helium nuclei formed from nuclear fusion of hydrogen are able to overcome the electrostatic repulsions between themselves and further fuse to form heavier elements, up to iron. The Red super giant then implodes, ejecting the outer layers into space and a high speed, called a supernova.
What happens to the cores of Super Red Giants after a supernova occurs.
If the Mass of the core is greater than 1.44M and less than 3M, a neutron star is formed. If Mass is greater than 3M, a black hole is formed.
What is the emission line spectrum
The bright lines observed when the electron in an excited atom drops back down to its initial energy state and releases a photon with the energy required to move that electron up to its previous energy state.
What is the continuous spectrum
A spectrum of all visible frequencies and wavelengths
What is the absorption spectrum
Dark lines against a continuous spectrum, which represent the absorbed photons by cooler gases in the sun.
How can you detect elements in a star
The absorption line spectrum produced by analysing the light from a star. The dark lines can be checked against known emission line spectrums of elements to detect elements in the star.
