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final
test
29
Astronomy
Undergraduate 1
05/13/2008

Additional Astronomy Flashcards

 


 

Cards

Term
astronmoical units
Definition
1 equals average earth-sun distance=93 million miles or 150 kilometers
Term
light year
Definition

the distance light travels through space in one year

10 to the 13th km/yr

Term
nearest star other than our sun
Definition
proxima centauri is 4.2 light years away
Term

measuring distance to stars

(indirect methods)

Stellar Parallax

Definition

shift in apparent position caused by earth orbit

(determined by photographing nearby stars against the back drop of more distant objects)

Term
stellar brightness is controlled by what 3 factors?
Definition
1. how large the star is
2. how hot the star is
3. how far away the star is
Term
apparent magnitude
Definition
star brightness as it appears from earth with the unaided eye.
(brightest is 1st magnitude, faintest is 6th magnitude.) each goes up by 2.5x
Term
absolute magnitude
Definition
true brightness of stars
Term
lumiosity
Definition
brightness
Term
betelgeuse
Definition
520 light years away
Term
sun magnitudes
Definition
apparent= -26.7
absolute=5
Term
variable stars
Definition
stars that fluctuate in brightness are known as variables
Term
pulsating variables
Definition
fluctuate due to expansion and contraction
CLASSICAL CEPHEIDS
Term
eruptive variables
Definition
sudden brightening of a star called a nova
Term
stellar color and temperature
Definition
hot stars (30000K) emit dominantly short wave radiation appear BLUE
Term
stellar color and temp. cont'd
Definition
red stars (3000K) emit longer wave radiation because they are cooler.
Term
binary stars and stellar mass
Definition
18th century- astronomers discovered numerous star pairs.
Term
mizar
Definition
second star in the handle of the big dipper, is actually a double star.
Term
william herschel
Definition
revealed that many star pairs actually orbit each other.
United by mutual gravition
called visual binaries
50% of the stars in the universe are multiples
Term
binary star and star mass
Definition
determined by the size of their orbits
Term
nebula
Definition
accumulations of gas and dust in space
Term
bright nebula
Definition
glow because they are close proximity to a hot blue star
Term
emission nebula
Definition
gaseous masses composed mostly of hydrogen
Term
reflection nebula
Definition
reflected light from nearby stars
thought to be composed of dense clouds or dust
Term
dark nebula
Definition
not close enough to a bright star to be illuminated
appear as a dark mass or holes in the heavens
Term
star birthplaces
Definition
dark, cool, innerstellar clouds
called a protostar
Term
protostar stage
Definition
gravitational contraction continues
-when core reaches 10 million degrees K fusion begins
-a balance between gravity (squeezing) and gas pressure (expansion) is reached and it becomes a main sequence star
Term
main sequence stage
Definition
hydrogen burning continues for a few billion years
different stars age at different rates
hot massive blue stars only last a few million years
smallest red main sequence stars may last hundreds of billions of years
average star spends 90% of it's life as a hydrogen burning main-sequence star, when hydrogen depleted star evolves rapidly and dies
Term
red giant
Definition
inert helium core
all hydrogen in core is consumed
-hydrogen fusion still progressing in outer shell
-star's outer envelope is expanding
-as the star expands, it cools
-internal pressure is increasing until the star begins to consume carbon in its core
-eventually all usable nuclear fuel is consumed
-different types of stars die ar different rates
Term
burnout/death of a star
Definition
somewhat speculative
what we know is...
-a star, no matter what size will eventually exhaust its fuel supply
Low mass stars(<0.5*sun)
-may remain sequence for 100 billion years
-never become red giants because they do not achieve sufficient heat and pressure to fuse anything but hydrogen
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