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Flashcards in astronomy 1 Deck (35):

how old is the universe

14 billion years


what is cosmological redshift

galaxies emit light and expand into space, the wave length of light gets stretched
distant galaxies have larger redshirts then nearby galaxies


was is cosmic microwave background radiation(CMB)

leftover heat from the big bang - the early universe must have been very hot and it’s expanded since


what evidence supports he big bang theory

cosmological redshift and CMB


what does the big bang theory state

that 14 billion years ago the portion of the universe we can see today was very small and began at a point , and it has been expanding since


what does a spectrometer measure

measures all of the wavelengths of energy coming off an object , the patter is called a spectrum


what is a continuous spectra

produced by a glowing solid or liquid- a stars surface produces a continuous spectra


what is one problem that makes the big bang theory incomplete

doesn’t explain the exsistence of galaxies and large scale structure


what is the emissions spectra (bright line)

produced when a glowing gas emits energy at specific wavelengths characteristic of the elements composing the gas


what is the absorption spectra(dark line)

produced when a gas lies between the observer and the object emitting a continuous spectra
the wavelengths absorbed depends on the composition of the gas
used to classify stars


how can bright or dark line spectrums be used

can be used to determine the elemental composition of a star
each element has a distant spectral signature


what is the hubble constant (H)

rate the universe is expanding


how can u use the dark line spectra

can be used to measure an objects velocity
the change in wavelength can be used to calculate the amount of shift


what happens in a red shift
blue shift

the object is moving away
the object is moving toward us

more lines the spectra has the cooler the star


what is a galaxy

system containing billions of stars
basic building block of the universe


what are the 4 types of galaxies

barred spiral
irregular - based on shape


characteristics of a spiral galaxy

lens shaped disks
bright nucleus - made up of millions of stars
75% are this type
youngest galaxies and could have black holes st the center


characteristics of a barred-spiral galaxy

lens shaped disks
bright nucleus
has “arms” of stars and gas
the milky way is a barred spiral


characteristics of a elliptical galaxy

lens shaped
but no bright center or “arms”
contains little or no dust and gas
20% are these type


characteristics of an irregular galaxy

small and faint
lots of gas and dust
stars spread unevenly
least common
ex: magellanic clouds


physical properties of stars -size

size can vary greatly
may be smaller than earth or way bigger than our sun


density and elements of stars

stars are mainly hydrogen and helium
most stars are the density of our sun (1.4 g/cm3


star formation

starts as a nebulae -cloud of gas and dust
protostars-glowing cloud sections
eventually hot enough to become in a stable state
then moves into a main sequence star


what is a hertzsprung-russel diagram

plots stars using surface temp in kelvin and a stars absolute magnitude(luminosity)
shows what type of star it currently is
ALL stars start out on the main sequence


main sequence stars -

the larger the starting mass the hotter the star- the hotter the star the brighter the star


what is Plancks law

the higher the surface temp the bluer the star
the cooler the surface temp the redder the star


supergiants -

very large but cool
gives off lots of light due to their size



large but cool
gives off lots of light
not as bright as super giants


white dwarfs-

about the size of earth but way more dense
very hot
do not produce much light due to small size


what is stellar magnitude

measure of a stars brightness
ranked on a scale - negative means star is bright, positive means star is dim


apparent magnitude -

how bright a star looks in the sky from earth
stars that are close are bright, vise versa


absolute magnitude-

scale compared all stars as if they were the exact same distance from earth
distance is 10 parsecs


what is a variable star

a main sequence star whose brightness changes in a cycle


why do stars vary in magnitude

a variable star expands and contracts
expansion makes the stars cooler and therefore dimmer - magnitude decreases
contraction makes them hotter -> brighter moves toward negative


why are variable stars useful

can be used to determine distances of galaxies
gives insight to how stars evolve