Chapter 19 stars Flashcards
What is a planet?
Object with sufficient mass for its own gravity to collapse it into a spherical shape
It’s orbit is clear of objects
Fusion reaction does not occur
What is a planetary satellite?
Bodies that orbit planets. Can be artificial or natural
Comets
Small irregular bodies made of rock, ice and dust.
Orbit the sun in eccentric elliptical orbits
Range from a few hundred metres to tens of kilometres across
Solar system
Systems containing starts and bodies orbiting them
Galaxies
A very large amount of interstellar dust, stars, gas and other bodies.
Each galaxy contains about 100 billion stars
Formation of stars up to nuclear fusion
nebulae are large clouds of dust and gas
over large periods of time gravity clumps gas together
more clumped = fasdter gravitational collapse
gpe converted to thermal energy, produces pressure and heat
a sphere of dense and hot gas called protostar formed
when core is hot enough hydrogen nuclei is converted to helium nuclei once electeostatics forces are overcome
this is called nuclear fusion and the main sequence star has formed
gas pressure from nuclei and radiation pressure from photons emitted during fusion balance gravitational force
evolution of low mass stars
Stars with 0.5 - 10 solar masses are low mass stars
Once they run out of helium, radiation and gas pressure no longer balance gravitational forces, so the star core collapse inwards.
Fusion of still occurs only in a shell around the shrinking core, not in the core itself as the temp is too low
the rest of the outer shells drift of into space as planetary nebula
the core becomes a white dwarf
chandrasekhar limit
maximum stable mass of a white dwarf
once the star collapses into a white dawrd electron degeneracy pressure(two electrons cannot exist in the same place) prevents the core from collapsing further
if the star is less than 1.44 solar msasses this applies.
evolution of high mass stars
as hydrogen runs out, temperature is high enough
for helium nuclei to fuse into heavier elements
several shells of elements from an iron core then less heavy is created
when core becomes iron no more fusion occurs,so core becomes unstable
a massive shockwave occurs, where heavy materials are produced
when do you get a white dwarf, neutron star, or black hole
white dwarf when low mass star runs out of hydrogen
neutron star when high mass star runs out of hydrogen but remaining core is greater than 1.44sm
Black hole when high mass star has core greater than 3 solar mass
Energy levels in gas atoms features
electrons cant have a quantity of energy between two energy levels
The energy level is negative as energy is required to remove the electron
Wiens law
The maximum wavelngth at a given tempertauture is estimated as kMAX = 0.0029/T
