Astrophysics Flashcards
Discuss 2 different ways in which atomic spectra can be used to deduce physical data for stars
- Temperature - calculated from λ max
- types of elements that exist in the stars by seeing what wavelength is missing we can find out what wavelengths
why the method of parallax can be used for stars @ a distance of less than a few 100 parsecs from Earth?
beyond this distance the parallax angle is too small to be measured accurately /is less than the uncertainty of the measurement
what property determines whether a star ends its life as a white dwarf or as a neutron star
mass of star
life cycle of stars (draw)
on ipad
state 4 properties of red giants
- red in colour
- large mass
- large surface area
- are in the late stage of star life
state 4 properties of red super giants
- red in colour
- larger mass than the red giant
- larger surface area than the red giant
- are in the late stage of star life
white drawfs (5 properties)
- white in colour (relatively hot)
- a small mass
- small surface area
- the final stage of the life cycle of smaller stars
- no longer undergoing fusion
cepheid variables state 3 properties and draw the cycle it undergoes
- unstable
- regular variations in luminosity (L) and brightness due to a periodic variation in size
- late stage in the life cycle of some stars
drawing on ipad
what is the Chandrasekhar limit
white dwarf stars have a max mass of 1.4 M this is due to electron degeneracy pressure
what is Oppenhelmer Volkoff limit?
Inside a neutron star protons and electrons are forced together by gravity to form neutrons. neutrons degeneracy pressure
what are pulsars
neutron stars will cool over time and as they are no longer producing heat they will emit energy as radio waves. if they are rotaing they will emit this energy in bursts and are pulsars.
stars life cycle on an H-R Diagram (low mass star)
On iPad
stars life cycle on an H-R diagram (High mass star)
On iPad
Why is newtons model of the universe wrong
Newton believed that the universe was: Infinite in space
infinite in time
uniform
static
However the sky was dark at night, using the inverse square law the apparent brightness of those stars on is proportional to 1/r^2
this means that every shell, no matter how far it is, will be equally bright. if the universe is infinite then there will be an infinite number of shells and the sky should be infinitely bright… but its not. Therefore the universe cannot be infinite (in neither space nor time). A different model of the universe is needed.
outline how the big bang model of the universe is consistent with this statement: observation of the night sky indicates that there are many regions of the universe that do not contain any stars.
Space and time originated with the big bang theory
1. Universe is expanding
2. Due to expansion light has not yet reacted from distance stars / or has been red-shifted and is not visible
