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Unit 11
Stellar Evolution
35
Astronomy
Undergraduate 2
11/12/2012

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Cards

Term
In terms of nuclear reactions, what is the next stage of a star's life after the end of hydrogen burning in the core?
Definition
Hydrogen burning in a thin shell around the core
Term
The next stage in a star's life after the main sequence phase is
Definition
the red giant phase
Term
The age of a cluster can be determined by
Definition
measuring the age of the stars that are still on the main sequence
Term
What are the main products of helium nuclear fusion in red giant stars?
Definition
carbon and oxygen nuclei
Term
A planetary nebula is a(n)
Definition
expanding gas shell surrounding a hot, burned-out stellar core
Term
What process marks the end of a star's 'middle age' and moves it off of the main sequence?
Definition
The build up of inert helium in the core, which creates a hydrogen fusion shell.
Term
A planetary nebula is mostly made up of material from a star's
Definition
outer atmosphere
Term
What elements would you expect to make up the material of an expanding planetary nebula?
Definition
hydrogen, helium, carbon and oxygen
Term
A white dwarf is (in terms of luminosity and temperature compared with original star)
Definition
is hotter and less luminous than the star it came from
Term
A white dwarf
Definition
is the core of a star which has ejected a planetary nebula
Term
Stars with between 0.4 and 8 solar masses will not fuse elements heavier than helium because
Definition
they will never create a high enough core temperature to fuse helium
Term
A star will only fuse elements heavier than Helium if
Definition
its core temperature gets hotter than about 600 million K
Term
A planetary nebula is
Definition
ejected gas that will keep moving outward and will eventually become too thin to see
Term
The processes that cause the evolution of a star off of the main sequence have to do with
Definition
the fusion of elements other than hydrogen in the star's core
Term
Most stars in the universe will end their lives as
Definition
a planetary nebula
Term
As a star evolves to become a red giant it will become
Definition
cooler and more luminous
Term
The first major stage in the aging of out sun will happen when
Definition
helium in the Sun's core pushes hydrogen fusion into a spherical shell around the core
Term
White Dwarfs
Definition
will eventually cool off and form black dwarfs
Term
Why does an aging star turn into a supernova?
Definition
The fusion of iron in the star's core pulls the material of the star inward, creating a blast wave which removes the outer part of the star
Term
Why does a star expand into a Red Giant?
Definition
the change of the core structure to allow hydrogen shell-burning changes the energy balance pushing the atmosphere outward.
Term
Why are Carbon and Oxygen a main component of planetary nebulae and supernova remnants?
Definition
They are products of helium fusion, the first stage of stellar evolution process
Term
Stellar death is important for stellar birth because
Definition
The shock way from supernovae can cause gas clouds to collapse producing new stars
the heavy elements produced in the star's core adds to the variety of elements in the ISM
Term
What property of a star determined whether it will form a planetary nebula or supernova?
Definition
mass
Term
Elements heavier than hydrogen
Definition
fuse at higher temperature than hydrogen and produce less energy
Term
On an H-R diagram, white dwarfs are
Definition
hot and dim
Term
Supernovae are
Definition
some of the most energetic and violent processes in the universe
Term
What type of remnant will be produced by a high mass star (between 8 and 20 times the mass of the sun)?
Definition
a neutron star
Term
What type of remnant will be produced by a sun-like star (between than 0.4 and 8 times the mass of the sun)?
Definition
a white dwarf
Term
What type of remnant will be produced by an ultra-low mass star ( smaller than 0.4 times the mass of the sun)?
Definition
a cold object made entirely of helium
Term
What type of remnant will be produced by an ultra-high mass star (larger than 20 times the mass of the sun)?
Definition
a black-hole
Term
What kind of nebula cannot be seen in visible light?
Definition
dark nebula
Term
What kind of nebula takes the form of an irregular shaped object with a strong blue color?
Definition
reflection nebula
Term
What kind of nebula takes the form of strong, chaotic filamentary structure showing a variety of colors, with strong emissions in bands of the spectrum as high as X-rays?
Definition
supernova remnant
Term
What kind of nebula takes the form of a spherical or hourglass shaped object with strong ted edges and possibly a greenish interior?
Definition
planetary nebula
Term
What kind of nebula takes the form of an irregularly shaped object with a strong red color?
Definition
emission nebula
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