Stars Flashcards
What is a meteroits
Bits of asteroid or bits of rock which make it through the journey of the earths atmosphere and the to the surface
Define a planet
An object with sufficient mass for their own gravity force to make them a spherical shape where no nuclear fusions occur and the object has cleared its orbit of other objects
What is a dwarf planet
Planets where the orbit has not been cleared of other objects
what are asteroids
objects which are too small or too uneven in shape to be planets with a near circular orbit around the sun
what are comets
small irregularly sized balls of rock,dust and ice
give the timeline for the evolution of a low mass star and give the size
Nebula, protostar, Main sequence star, Red giant, white dwarf, black dwarf
from 0.5- 10 solar masses
give the timeline for the evolution of high mass stars
Nebula, protostar, Main sequence, Red super Giant, supernova, Neutron star, black hole
what is nebula
gigantic clouds of dust and gas, over millions of years the gravitational attraction between the particles pulls them together to form clouds. As they come closer together the gravitational collapse accelerates and some regions become denser and pull in even more dust and gas. this energy is then converted to thermal energy
what happens after the gravitational energy converts into thermal energy in the nebula
a protostar is formed,
what is required in the protostar for a star to e formed
the temp and pressure must be high enough for the hydrogen nuclei in the protostar to overcome the electrostatic forces of repulsion and undergo nuclear fusion, producing helium producing a star
what happens in the main sequence star phase how is this stage different in larger stars
the star is in a stable equillibrium where the gravitational forces of the particles act to compress the star but are counteracted by the radiation pressure from the photons emitted in fusion and gas pressure from the nuclei
in larger stars they are hotter therfore this stage is shorter as they undergo faster fusion
what is the solar mass equal to
= 1.99 x 10^30 kg
explain what happens after the main stage of a low mass star
once the hydrogen supply is low the gravitational forces inwards overcome the radiation and gas pressures so the star collapses inwards and evolve into a red giant (cooler ) the core of the red giant is too cool for fusion to occur, but the pressure in the outer layers is great enough for fusion to occur.
what happens after the red giant phase for a low mass star
fusion occurs in the outer layers but not in the core, so the giant evolve into a hotter white dwarf as the outer shells drift off as planetary nebula , the core remains dense which has a very high temp
what happens in the white dwarf in low mass stars
the photons which were produced leak out dissipating heat and the core starts collapsing however electron degeneracy prevents the core from collapsing completely. and as long as the mass of the core is less than 1.44 solar masses the white dwarf is stable
what is electron degeneracy
where 2 electrons can not exist in the same state
what happens after the amin stage for a high mass star
stars which are larger than 10 solar masses, after the main phase will have a high enough temp for helium fusion into heavier elements producing elements upto iron
why does fusion only happen upto iron in high mass stars after main stage
iron does not release energy therfore can not fuse further
what happens after iron is prod high mass star
the star becomes unstable and a type2 supernova occurs where there is a shockwave which ejects materials into outer space and the core collapses however elements hevier than iron can be formed in supernovas
what happens after the supernova
high mass stars
if the remaining core mass is larger than 1.44 solar masses protons and electrons combine to become neutrons producing an extremely small neutron star and if the remaining mass is more than 3 solar masses it will become a black hole where light can not escape
When does an electron get excited
When it is going from a lower energy level to a higher one
What happens when an electron moves towards the ground state
It gets de-excited and releases energy in the form of a photon with a specific wavelength
State the conditions for electron in energy levels
Electrons can only exist in one of a no. Of discreet levels ( energy level)
Electrons can not have an energy value in between 2 levels (discrete levels)
All electrons bound to the atom have -ve energy values as they would need to give energy to return to 0 ( to escape atom)
The ground state (the lowest energy level) is the most -ve value
What is required for an electron to go to a higher energy level
Absorbing a photon of the exact energy value of the enrgy value (discrete)
Where is the ground state in a n atom
The energy level closest to the nucleus
Describe a continuous line spectra
All visible wavelengths of light are present produced by atoms of solid heated metals
Describe absorption line spectra
A series of dark spectral lines against the background of the continuous spectrum with each line corresponding to a wavelength used to excite that element
What is the enrgy released by a debited electron equal to
The difference between the electrons initial energy level and its final energy level of the photon
What is a diffraction grating
Components it’s regularly spaced slits that can diffract light
What is weins law
The black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object
Lambda max x absolute temp= Weins constant
Whims constant= 2.9x10^-3 mK
What is lambda max in wines equation
The wavelength of the ight prod. With the maximum intensity peak of intensity/wavelength graph
What is stefans law
For a black body the total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature
Units of luminosity= watts
Describe the characteristics of a main sequence star
Converts hydrogen into helium in their core
Maintains a constant luminosity
Describe the lifecycle of the sun
Currently in its main sequence hydrogen is fusing into helium releasing more energy, maintaining luminosity, inwards and outwards forces balanced
As hydrogen runs out less outwards pressure therfore sun cools down and collapses due to gravitational force
Becomes a reg giant and core becomes hot enough for for helium fusing , then helium starts to run pout so it collapse agin
The outer layer drift out as nebula into space and becomes hotter white dwarf however temp does nt rise high enough for more fusion
State and explain the conditions necessary for fusion to occur in a star
High temps so nuclei can be close enough to fuse and overcome the electrostatic forces between nuclei
High density for high pressures for sufficient collision rates
