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54 Cards in this Set
- Front
- Back
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celestial sphere
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huge imaginary dome with earth as center; stars appear to be mounted
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declination
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celestial latitude on celestial spherel
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right ascension
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celestial longitude on celestial sphere
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celestial prime meridian
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half-circle that passes thru vernal equinox, north celestial pole, and south celestial pole
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ecliptic
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path the Sun traces annually on the celestial sphere
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celestial equator
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extension of earth's equator on celestial sphere
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light year
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distance light travels in time of 1 year
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parsec
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distance to a star that exhibits a parallax of 1 sec of arc
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absolute magnitude
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brightness a star would have at distance of 10 pc
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apparent magnitude
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brightness of a celestial object from earth; original scale from hipparchus
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h-r diagram
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chart obtained when absolute magnitude of stars is plotted against their temperature
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red giants
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large, cool stars to the upper right on the h-r diagram
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main sequence
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narrow band of stars going from upper left to lower right on h-r diagram
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nebulae
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cool, dense clouds of gas and dust in space
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brown dwarfs
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failed stars
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protostar
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name given to condensed nebula before it becomes a star
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planetary nebulae
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shell of material ejected from a variable star late in its life
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white dwarfs
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hot, small, very dim stars formed at the end of low-mass star's lives
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nova
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small nuclear explosion on surface of white dwarf
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supernova
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most catastrophic explosion of high-mass star, end results are either neutron star or black hole
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neutron star
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super dense star of which pulsars are one type
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pulsar
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fast rotating neutron star that radiates radio waves in rotating pattern
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black hole
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object so dense that not even light can escape its gravity
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singularity
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extremely dense point at center of black hole
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event horizon
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boundary around black hole from which no matter or radiation can escape from
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schwarzschild radius
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distance from black hole's singularity to its event horizon
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nucleosynthesis
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creation of nuclei of elements inside stars
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sunspots
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dark patches of cooler material on surface of the sun
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flares
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material explosively ejected in space from sun's surface
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prominences
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enourmous filaments of excited gas that arch over and return to sun's surface
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chromosphere
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layer of sun above photosphere, temp 50,000 K
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corona
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sun's most outer layer, origin of solar wind
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core of sun
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interior of sun where nuclear reactions convert hydrogen to helium and energy, core temp 15 mil K
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photosphere
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bright visible surface of sun, temp 6000 K
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age of our sun
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5 billion years
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proton-proton chain
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the series of three reactions by which hydrogen is fused into helium in the sun
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milky way galaxy
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galaxy which contains our solar, a spiral galaxy with massive black hole at its center
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globular clusters
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densely packed region of stars
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galaxy
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extremely large collection of stars
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universe
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totality of all matter, energy, and space
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local group
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40 or so galaxies of which milky way is member
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elliptical galaxy
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galaxy with an elliptical shape
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irregular galaxy
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galaxy with no regular shape
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normal spiral galaxy
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galaxy with disk shape, central bulge and curved spiral arms
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barred spiral galaxy
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spiral galaxy with two broad bars extending from opposite sides of central bulge, spiral arms extend from ends of bars
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quasars
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believed to be cores of galaxies that were formed when universe way young, extremely strong sources of radio waves, most distant objects in universe
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age of universe
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13.7 billion years
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big bang
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astronomers best theory of origin of universe. universe was extremely condensed and hot billions of yrs ago and has been expanding and cooling ever since
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Evidence for big bang
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cosmological redshift, cosmic microwave, background radiation, 3:1 ratio of hydrogen to helium in universe
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hubble's law
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greater the recessional velocity of a galaxy, the farther away it is
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cosmology
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studies structure and evolution in universe
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dark matter
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mysterious, unseen matter that accounts for about 23 percent of mass of universe
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cosmic microwave background
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radiation coming from all directions in space as a consequence of big bang
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dark energy
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mysterious energy that seems to cause acceleration of expansion of universe
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