modern earth science chapter 27: stars and galaxies Flashcards

Terms Definitions
absolute magnitude
a measure of the amount of light that a star actually emits
apparent magnitude
the brightness of a star when viewed from Earth
barred spiral galaxy
A galaxy that is similar to a spiral galaxy, except that the spiral arm pattern originates from a bar of material that passes through the nucleus of the galaxy.
binary star
a system of two stars that revolve around each other under their mutual gravitation
black hole
remnant of a star that is so dense that nothing, not even light, can escape its gravity field
circumpolar
describing any star that is always visibel in the night sky, in the Northern Hemisphere that circles around polaris
constellation
A group of stars that form a pattern in the sky
elliptical galaxy
A spherical or elongated galaxy with a bright center and very little dust and gas - no young stars
galaxy
a collection of star systems
giant
a very large, cool, bright star
globular cluster
spherically shaped group of hundreds of stars located around the core of the Milky Way Galaxy
H-R diagram
Hertz sprung-Russell diagram, a graph that shows the relationship between magnitudes and temperature.
irregular galaxy
galaxy with no definite shape - tend to be smaller and fainter
light-year
Distance light travels in a year
main-sequence star
star with characteristics that place it within a band running thru the middle (diagonally) of the HR diagram
nebula
a large cloud of dust and gas that can break apart into smaller pieces and form stars
neutron star
collapsed core of a supernova that shrinks to about 20 km in diameter and whose dense core has only neutrons
nova
star that suddenly becomes much brighter and then returns to its original brightness
open cluster
cluster of only a few hundred stars, usually young, found only in the galactic disc, nearly only spiral arms, less dence than globular clusters
parallax
method of determining the distance from the earth to a star based on the shift in the apparent position of the star when viewed from different angles
planetary nebula
expanding shell of gases shed by a dying star
protostar
inside a nebula, the shrinking, spinning, center region - the 2nd stage in teh development of a star
pulsar
neutron star that emits two beams of radiation that sweep across space
quasar
starlike object that gives off radio waves and X rays
red shift
Name for the change in a star's spectrum when it moves away from Earth
spiral galaxy
a galaxy whose arms curve outward in a pinwheel pattern
star
a body of gases that gives off a tremendous amount of radiant energy in the form of light and heat
supergiant
life cycle stage of a massive star where the core reaches extremely high temperatures, heavy elements form by fusion, and the star expands
supernova
the brilliant explosion of a dying supergiant star
white dwarf
a small, hot, dim star that is the leftover center of an old star
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