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Exam 2 AST 112
Chapters 17-20
27
Astronomy
Undergraduate 1
03/17/2011

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Cards

Term
Parsec
Definition
Parallax in arc seconds
Term
Proper Motion
Definition
Measure of the star's velocity perpendicular to our line of sight
Term
Apparent Brightness
Definition
the rate at which energy from the star reaches a detector
Term
Magnitude Scale
Definition
system of ranking stars by apparent brightness
Term
Apparent magnitude
Definition
measure of apparent brightness
Term
Absolute magnitude
Definition
the apparent magnitude it would have if places at a standard distance of 10 pc from the viewer
Term
Photometry
Definition
the measurement of the amount of starlight received through each member of a set of filters
Term
Spectral classes
Definition
O, B, A, F, G, K, M
Term
Dwarfs
Definition
Stars comparable in size to, or smaller than, the Sun are called
Term
Giants
Definition
Stars up to 100 times larger than the Sun
Term
Stars more than 100 times larger than the Sun are called
Definition
Supergiants
Term
Red giants
Definition
large, cool, and luminous
Term
White dwarfs
Definition
small, hot, and faint
Term
Interstellar medium
Definition
Made up of gas and dust
Term
Extinction
Definition
general diminution of starlight by dust
Term
Nebula
Definition
general term for any fuzzy bright or dark patch in the sky
Term
Emission nebulae
Definition
extended clouds of hot, glowing interstellar gas
Term
Dark dust clouds
Definition
irregularly shaped regions in the interstellar medium whose constituent dust diminishes or obscures light from background stars
Term
Protostar
Definition
warm, very luminous object that emits mainly infrared radiation
Term
zero-age main sequence
Definition
the region in the H-R diagram where stars lie when the formation process is over
Term
Brown dwarfs
Definition
fragments of collapsing gas and dust that did not contain enough mass to initiate core nuclear fusion
Term
Shock waves
Definition
young hot stars ionize the surrounding gas, forming emission nebulae
Term
Core-hydrogen-burning
Definition
stably fusing hydrogen into helium at their centers
Term
Hydrogen-shell-burning
Definition
the nonburning helium at the center is surrounded by a layer of burning hydrogen
Term
Black dwarf
Definition
The white dwarf cools and fades
Term
Roche lobe
Definition
the region of space within which matter belongs to the star
Term
Mass-transfer binary
Definition
gas flows from the giant onto its companion
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