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Science > astronomy 1 > Flashcards

astronomy 1 Flashcards

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1
Q

how old is the universe

A

14 billion years

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2
Q

what is cosmological redshift

A

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

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3
Q

was is cosmic microwave background radiation(CMB)

A

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

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4
Q

what evidence supports he big bang theory

A

cosmological redshift and CMB

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5
Q

what does the big bang theory state

A

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

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6
Q

what does a spectrometer measure

A

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

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7
Q

what is a continuous spectra

A

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

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8
Q

what is one problem that makes the big bang theory incomplete

A

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

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9
Q

what is the emissions spectra (bright line)

A

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

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10
Q

what is the absorption spectra(dark line)

A

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

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11
Q

how can bright or dark line spectrums be used

A

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

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12
Q

what is the hubble constant (H)

A

rate the universe is expanding

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13
Q

how can u use the dark line spectra

A

can be used to measure an objects velocity

the change in wavelength can be used to calculate the amount of shift

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14
Q

what happens in a red shift

blue shift

A

the object is moving away
the object is moving toward us

more lines the spectra has the cooler the star

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15
Q

what is a galaxy

A

system containing billions of stars

basic building block of the universe

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16
Q

what are the 4 types of galaxies

A

spiral
barred spiral
elliptical
irregular - based on shape

17
Q

characteristics of a spiral galaxy

A

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

18
Q

characteristics of a barred-spiral galaxy

A

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

19
Q

characteristics of a elliptical galaxy

A

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

20
Q

characteristics of an irregular galaxy

A 
small and faint 
lots of gas and dust 
stars spread unevenly 
least common 
ex: magellanic clouds
21
Q

physical properties of stars -size

A

size can vary greatly

may be smaller than earth or way bigger than our sun

22
Q

density and elements of stars

A

stars are mainly hydrogen and helium

most stars are the density of our sun (1.4 g/cm3

23
Q

star formation

A

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

24
Q

what is a hertzsprung-russel diagram

A

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

25
Q

main sequence stars -

A

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

26
Q

what is Plancks law

A

the higher the surface temp the bluer the star

the cooler the surface temp the redder the star

27
Q

supergiants -

A

very large but cool

gives off lots of light due to their size

28
Q

giants-

A

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

29
Q

white dwarfs-

A

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

30
Q

what is stellar magnitude

A

measure of a stars brightness

ranked on a scale - negative means star is bright, positive means star is dim

31
Q

apparent magnitude -

A

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

32
Q

absolute magnitude-

A

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

33
Q

what is a variable star

A

a main sequence star whose brightness changes in a cycle

34
Q

why do stars vary in magnitude

A

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

35
Q

why are variable stars useful

A

can be used to determine distances of galaxies

gives insight to how stars evolve

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