Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
33 Cards in this Set
- Front
- Back
|
what are planetary nebulea?
|
the glowing layers of gas cloud that are ejected at the end of AGB evolution
|
|
|
what is at the center of a planertary nebulea?
|
we see the burned out cores of the AGB stars, very hot and luminous at first, but no longer able to produce power by fusion
|
|
|
when does the mostly oxygen core become visible in a solar neb?
|
when the ejected gas recombines (the atomic nuclei and electrons combine to form neutral atoms that are transparent)
|
|
|
in 50,000 years what is going to happen to the planatary neb
|
it is going to evolve into a white dwarf
|
|
|
what happens to the central star as it cools in the neb?
|
the excitation for the nebular gas is removed
|
|
|
why is the gas envelope bright red?
|
the uv radiation from the central star excites the atoms
|
|
|
central stars of the planetary neb are?
|
the very hot cores of red super giant coressurface temp in excess of 100,000k are measured in planetary neb
|
|
|
why will the central stars of a planetary neb be cool?
|
thre is no energy generated in their cores and become white dwarfs as their surface temp decreases
|
|
|
what happens to mass of a star during stellar evolution?
|
stars can loose up to 80% of their orignal mass
|
|
|
degenerate electron pressure can not ssupport a white dwarf with a mass of more then
|
1.4 solar masses- Chandrasekhar solar limit
|
|
|
how much more dense are white dwarfs then earth
|
1 billllllion
|
|
|
what is never reached in white dwarf stars or the interior of stars that become white dwarfs
|
the minimum temp for oxygen fusion and carbon
|
|
|
what can white dwarfs do that are in close bianary systems?
|
get matter from the nearby normal star and the explosive hydrogen fusion produces a nova which makes the star survive
|
|
|
what is the core like of massive stars in late evolution?
|
like an onion with shell fusion in multipleshells around an increasingly massive iron core the surrounding envelope is huge
|
|
|
what is the iron core produced by?
|
silicon fusion that only lasts about a day on 25 solar mass star
|
|
|
what happens in the core bounce process?
|
The infalling matter is met by the expanding core and out flowing neutrinos resulting in a tremendous outflow of matter
|
|
|
what happens to the matter from the super nova to enrich stellar the inerstellar medium?
|
to ejects
|
|
|
what does a collapsing iron core do?
|
starts a supernova explosion
|
|
|
why can't iron be fused to heavier atomic nuclei?
|
it is the most tightly bound of all nucleis
|
|
|
protons and electrons collide through
|
nuclear reaction that emits a neutrino and electron becomes a neutron
|
|
|
what does the core of a supernova become?
|
mostly a collection of neutrons mass of 1 to 3 solar masses
|
|
|
what is a super nova
|
a major explosion of a star
|
|
|
what happens in a white dwarf super nova- type ia
|
white dwarf explodeds as the carbon and oxygen fuses to make iron and radioactive isotopes of nickel and colbalt
|
|
|
what do a supernova of type II (strong hydrogen lines in their spectra) leave behind
|
a neutron star
|
|
|
what is the limit of mass of neutron stars
|
around 3 solar masses
|
|
|
what are pulsars
|
rotating magnetized neutron stars produce a lighthouse affect
|
|
|
what is the crab nebula?
|
the remanets of an explosion contains a short period pulsar
|
|
|
wat is the the escape velocity of a neautron star
|
1/2 the speed of light
|
|
|
what is the escape velocity of a black hole?
|
like the speed of light at a horizontal horizon
|
|
|
in einstiens theory of general relativity what is gravity
|
a force not a feature
|
|
|
what does the center of a black hole contain
|
singularity where all the mass is concentrated in a point
|
|
|
the radius of an event horizon
|
schwarzchild radius
|
|
|
theories predict that stars of what atomic mass can produce black holes
|
25 sm
|
