Astronomy Flashcards
absolute magnitude
a brightness scale used to measure how bright a star would be if it were seen from a standard distance
apparent magnitude
the brightness of a star as seen from Earth
galaxy
a large collection of stars dust and gas bound together by gravity
H-R Diagram
Hertzsprung-Russell diagram, a graph that shows the relationship between a star’s surface temperature and absolute magnitude
light-year
the distance that light travels through space in one year; about 9.46 trillion kilometers
luminosity
the actual brightness of an object such as a star
main sequence
the region of the H-R diagram where stars spend most of their lives; it has a diagonal pattern
nebula
a large cloud of dust and gas in interstellar space; a region in space where stars are born
neutron star
the core of a supernova that has collapsed under gravity to the point that the electrons and protons have smashed together to form neutrons
planet
a relatively large spherical body that orbits a star
pulsar
a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation
revolution
the motion of a body that travels around another body in space; one trip along an orbit
rotation
the spin of a body on its axis
solar system
the collection of large and small bodies that orbit our central star, the sun
star
a large celestial body that is composed of gas and that emits light; the sun is a typical star
wavelength
the distance between two adjacent troughs or crests of a wave
supernova
a gigantic explosion in which a massive star throws its outer layer into space, but its core remains
universe
space and all the matter and energy in it
white dwarf
the hot, dense, dim core of matter that remains from the collapse of a low-mass star
elliptical galaxy
a spherical or elongated galaxy with a bright center and very little dust and gas
spiral galaxy
a galaxy shaped like a pinwheel, with a bulge in the center and spiral arms extending outward
irregular galaxy
a galaxy with irregular shap that does not fit into any other category
electromagnetic spectrum
all of the different wavelengths and frequencies of electromagnetic radiation, from radio waves to gamma rays
big bang theory
the theory that all matter in the universe was compressed into an extremely small volume that 13 to 15 billion years ago exploded and began expanding in all directions
cosmic microwave background
CMB; the electromagnetic radiation left over from the formation of the universe
red shift
a phenomenon which occurs when a star or galaxy is moving away from the Earth
doppler effect
an observed change in frequency or wavelength when the source is moving with respect to the observer
