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| A star with a main sequence mass of less then about 8 solar masses |
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| Mass-Luminosity relationship |
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| An empirical relationship between the luminosity (L) and the Mass (M) of main-sequence stars expressed as a power law |
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| How quickly a star runs out of fuel depends on it's __ and __ |
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| The path that a star follows across the H-R diagram as it evolves through its lifetime |
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| Describing the state of material compressed to the point at which electron density reaches the limit imposed by the rules of quantum mechanics |
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| The fusion of hydrogen in a shell surrounding a stellar core that may be either degenerate or fusing more massive elements |
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| A low-mass star that has evolved beyond the main sequence and is now fusing hydrogen in a shell surrounding a degenerate helium core |
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| A region on the H-R diagram defined by low-mass stars evolving from the main sequence toward the horizontal branch |
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| The nuclear fusion reaction that combines 3 helium nuclei (alpha particles) together into a single nucleus of carbon. |
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| An evolving low-mass star moves __ and to the __ on the H-R diagram |
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| The runaway explosive burning of helium in the degenerate helium core of a red giant star |
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| A ___ is a thermonuclear runaway--an explosion within the star |
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| A region on the H-R diagram defined by stars burning helium to carbon in a stable core |
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| Horizontal branch stars burn __ in the core and __ in the shell |
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Definition
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| asymptotic giant branch (AGB) |
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Definition
| The path on the H-R diagram that goes from the horizontal branch toward higher luminosities and lower temperatures, asymptotically approaching and then rising above the red giant branch |
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| The star forms a degenerate __ core as it leaves the horizontal branch |
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| The loss of mass from the outermost parts of a star's atmosphere during the course of its evolution |
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| The expanding shell of material ejected by a dying asymptotic giant branch star. A planetary nebula glows from fluorescence caused by intense ultraviolet light coming from the hot, stellar remnant at its center |
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| The stellar remnant left at the end of the evolution of a low-mass star. A typical white drawf has a mass of 0.6 solar mass and a size about equal to that of Earth; it is made of nonburning, electron-degenerate carbon |
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| A group of stars that all formed at the same time and in the same general location |
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| The strip on the H-R diagram plotting where stars of all masses in a cluster begin their lives |
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| The location on the H-R diagram of a single aged stellar population( such as a star cluster) where stars have just evolved off the main sequence. The position of the main sequence turnoff is determined by the age of the stellar population |
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| The hourglass or the figure eight-shaped volume of space surrounding two stars, which constrains material that is gravitationally bound by one or the other |
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| the transfer of mass from one member of a binary star system to its companion. Mass transfers occur when one of the stars evolves to the point that it overfills its roche lobe, so that its outer layers are pulled toward its binary companion |
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| A stellar explosion that results from runaway nuclear fusion in a layer of material on the surface of a white dwarf in a binary system |
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| Runaway burning of ___ on a white dwarf causes a nove |
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| The mass of a white dwarf cannot exceed ___ |
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Definition
| The upper limit on the mass of an object supported by electron degeneracy pressure; approx 1.4 solar mass |
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| A supernova explosion in which no trace of hydrogen is seen in the ejected material. Most type Ia supernovae are thought to be the result of runaway carbon burning in a white dwarf star onto which material is being deposited by a binary companion |
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| Study evolution of stars using computer models similar to: |
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| A stars ____ determines what life path (evolutionary track) it will take |
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stars are divided into 2 groups:
1.) low mass ____
2.) high mass____ |
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Definition
1.) .08 solar mass < m < 8 solar mass
2.) M > 8 solar masses |
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| ___ of different masses follow different paths on their way to the main sequence |
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| Curves of constant age for range of initial masses (not same as evolutionary tracks) |
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| ___ stars convert hydrogen to helium in their cores (=hydrogen core burning) |
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Nuclear reactions depend on a star's central temperature, which depends on its mass:
-less massive stars:
-more massive stars:
-in between: |
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Definition
proton-proton chain
CNO cycle/ Carbon cycle(later)
mix of P-P and CNO |
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| Internal structure is different for main sequence stars of different masses, partly because of ___ differences |
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| How long do these stars stay on the main sequence? |
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Definition
| Until they burn up their core fuel (hydrogen 10%) |
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| Massive stars have more fuel, but they are also much ___, so they use it up faster |
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Definition
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| Stars with higher ___ burn their fuel more quickly |
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Definition
| masses(mass-luminosity relation) |
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| ___ stars fuse hydrogen (H) to helium (He) in their cores, eventually much of the core H is converted to He. |
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| An expanding ___ has a contracting inert helium core surrounded by a hydrogen burning shell. |
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| The more massive low-mass stars, including the sun, continue to expand and become more luminous as their cores keep contracting, and heating up, becoming ____ |
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EVOLUTION OF LOW MASS STARS
stages in order: |
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Definition
| Main sequence star, Red giant branch star, Helium flash, Horizontal branch star, Asymptotic giant branch star, Planetary nebula ejection, white dwarf |
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In the part-degenerate core of Red giants, the core temp. climbs but the core does not ___.
Energy generation is very ___-sensitive, runs away as (above black) increases |
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Definition
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| The prostar's energy source is ___ |
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Definition
| gravitational potential energy |
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Term
ELECTRON DEGENERACY PRESSURE:
packing more electrons into a given volume means putting them in higher and higher momentum levels.
electrons resist being put in higher levels-->pressure.
Pressure depends only on ___, not on temperature |
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Definition
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| Core of red giant will stabilize, and as it does the outer layer shrinks, and the star relocates itself on the H-R diagram as a ___ star |
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