Test Questions on astronomy – Astronomy – Flashcards
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what is the evidence for dark matter in galaxies
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rotation curves of galaxies are flat, indicating that most of their matter lies outside their visible regions
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dark matter
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an undetected form of mass that does not emit light but whose existence we infer from its gravitational influence
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dark energy
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an unknown form of energy that seems to be the source of a repulsive force causing the expansion of the universe to accelerate
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the energy of the universe is roughly:
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2/3 dark energy; 1/3 matter
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three ways to find cluster mass
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1) velocity of galaxies 2) mass traced through x-ray 3) gravitational lensing
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two types of dark matter
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1) ordinary dark matter (MACHOS) massive compact halo objects 2) extraordinary dark matter (WIMPS) weakly interacting massive particles
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what is the role of dark matter in galaxy formation
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it is the thing that dictates galaxy formation
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spin
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initial angular momentum of protogalactic cloud could determine size and resulting disk. (galaxies)
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why do galaxies differ
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collisions
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cosmology
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is the study of the large-scale structure and evolution of the universe
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three tenets of cosmology
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1) we are not at a special place in the universe 2) the universe has no edges and no center-infinite in all directions. 3) the universe looks the same in all directions-it is isotropic(same in all directions)
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big bang theory
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theory that says the entire universe began at a single point of extremely high density and temp.
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what the early universe was like:
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must have been extremely hot and dense, with everything packed close together
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how did we get matter?
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photons converted into particle-antiparticle pairs and vise versa
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changes of the universe due to:
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cooling of the universe, and the decreasing density. density and temp are linked
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four know forces in the universe
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strong force electromagnetism weak force gravity
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GUT Era
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forces united(except gravity) into one force-possibly elementary particles
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Electroweak Era
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elementary particles
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particle era
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amounts of matter and antimatter nearly equal
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era of nucleosysthesis
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the creation of atomic nuclei(matter) nuclei begin to fuse.
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era of nuclei
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universe has become too cool to blast helium apart
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era of atoms
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background radiation released
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era of galaxies
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galaxies form
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why did we have to wait so long for galaxies and stars to form?
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the high temp in the early universe prevented stars forming
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evidence of the big bang:
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1) radiation from the big bang still detected 2) the elemental abundances that we measure agree with that expected 3) darkness of the night sky
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cosmic microwave background
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the radiation leftover from the big bang
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redshift
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as space between galaxies expands, it streches the light sent out by one galaxy by the time it reaches another far away galaxy. looks like redshift
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if the universe were older, how would the cosmic microwave background (CMB) spectrum be different?
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it would have a lower temp
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olbers' paradox
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if the universe were infinite, unchanging, everywhere the same, then stars would cover the night sky, and it would be as bright as the sun
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why is the night sky dark?
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according to olbers paradox, its because the universe changes with time
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why did the big bang theory only create hydrogen and helium?
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by the time helium was created, it was too cool to create heavier elements
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why cant we use parallax for very distant objects?
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their parallax is too small to measure
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how brightness distance and luminosity are related
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distance is proportional to brightness and inversely proportional to luminosity
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"standard candles"
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bright objects for which we know the luminosity of
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cepheid stars
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luminous stars at the end of their lives. their fusion is unstable and their luminosity fluctuates
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cepheids
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variable stars are very luminous, they can be seen in other nearbly galaxies
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doppler effect
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the motion of a light source toward or away from us changes the wavelength of the waves reaching us
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what direction is a galaxy moving from us if it is redshifted?
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away
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blueshift
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moving toward us
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hubbles law
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the further the galaxy is, the faster it is moving away
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what is causing the expansion of the universe
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dark energy
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how do we measure the distances to galaxies
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need to use standard candles. measure brightness, look up luminosity, compute distance
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will the universe continue expanding forever?
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yes
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"lookback time"
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the time it takes light to reach us
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looking back in time:
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the further an object is from us, the longer its light takes to reach us
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the most distant objects we can possibly see is how many light yrs
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13.7 billion light yrs. because this is the age of the universe
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fate of the universe
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if the universe has enough mass, gravity will eventually collapse it if the universe does not have enough mass, it will expand forever
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how could we measure the expansion of the universe?
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supernovae
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what are the basic necessities for life?
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maybe water, large planet, large moon, magnetosphere
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three major types of galaxies
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spiral, elliptical, irregular
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what are galaxies
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large grouping of 10^5 to 10^11 stars, gas, and dust held together by gravity
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how can we see a black hole
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x-ray flares from galactic center suggest that tidal forces of suspected black hole occasional tear apart chunks of matter about to fall in
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the bulge
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at the center of spiral galaxies
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if stars pass in and out of spiral arms, why dont we see many blue stars outside of spiral arms?
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blue stars die before the spiral arm passes
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is the milky way still making stars?
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yes; it has gas and dust
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what type of galaxy is the milky way?
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spiral
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how long does it take light to reach us
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8.5 mins
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what does a large scale structure of the universe look like
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super clusers and voids
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location
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universe-local group-milky way-solar system-earth
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when was universe created:
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14 billion years ago
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constellations
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loose grouping of stars that appear close together in the night sky
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asterism
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less formally defined grouping of stars that appear close together in the night sky
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celestial sphere
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model of the sky that helps us visualize the location and motion of the stars. ex:big dipper
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motion of stars:
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-24hrs moving -stars rise in the east and set in west. -appear to orbit the north celestial pole
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is the sun always found on the elliptical?
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yes. along with planets and moon; and signs of the zodiac
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summer solstice
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sun furthest north (longest days)
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autumnal equinox
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sun on equator (equal day and night)
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winter solstice
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sun furthest south (shortest days)
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moons revolution
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revolves every 29.5 days; therefore always see the same side of the moon
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waxing moon
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moon visible in afternoon/evening; gets fuller and rises later each day
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waning moon
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moon visible in late night/early morning; gets less full and sets later each day
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full moon
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rises at sunset and sets at sunrise
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new moon
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rises at sunrise and sets at sunset
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lunar eclipse
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when the shadow of the earth falls on moon; only at full moon
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solar eclipse
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shadow of the moon falls on the earth; only when new moon
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keplers laws
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1) orbits of the planets are ellipses with the sun at focus 2) equal areas in equal time 3) planets closer to the sun move faster
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laws of physics
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-as mass increases, so does gravitational force -as distance decreases, the gravitational force increases
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inverse square law
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where the quantity decreases with increased distance
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ideal gas law
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as pressure increases, so does temp
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true or false: wavelength is inversely proportionate to frequency
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true
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electromagnetic spectrum:
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- red light= longest wavelength - violet= shortest wavelength
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3 spectra:
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continuos, emission lines, absorption lines
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oldest telescope
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refracting; bends light using lens
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reflecting telescope
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reflects using mirrors
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gas cloud-protostar-planetesmial-accretion disk-planet
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...
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order of planets
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mercury, venus, earth, mars, jupiter, saturn, uranus, neptune
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why are there telescopes in space
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some atoms block radiation of certain wavelengths
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mercury
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basically the moon; no atmosphere
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venus
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very thick cloud layer; earths sister
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mars
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cold, large volcanos
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jupiter
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violent storms
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saturn
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rings, 30 moons
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uranus
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rotates on side, too faint for telescope
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neptune
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tugging uranus
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why does earth have water
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location in solar system; magnetosphere; atmosphere
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what is the moon made of
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rock and ice mixture
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what makes a planet
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orbit around the sun enough gravity to pull itself into a spherical shape cleared its orbit
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comet
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"dirty nucleus"
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layers of the sun
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core-radiation zone-convection zone-photosphere
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stars and their color
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red=cool yellow=medium blue=hot
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star formation
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form in massive clouds enough for gravity to overcome thermal pressure
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largest star
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150msun; any larger they blow apart
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smallest star
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.08msun; fusion required to begin
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interstellar medium
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dusty clouds that make stars and obscure our view because they absorb light
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what makes a star shine
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fusion
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what is latitude
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the specific position in the north-south direction
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what is the astronomical unit(AU)?
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the distance from the earth to the sun
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what is the elliptic
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the path of the sun throughout the year
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what causes the motion of the stars in the night?
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earths rotation on its axis
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the sun rises in the___ and the moon rises in the ____
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east; east
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zenith
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point directly above you
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why are there seasons?
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due to the tilt of earths axis; some areas of earth get indirect/direct sunlight
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absorption
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rays going outwards
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emission
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rays going inwards
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what spectral type is the sun
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G
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stars are formed from
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molecular clouds
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elements in order of decreasing abundance in universe
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hydrogen-helium-oxygen-iron
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what is the latitude of morgantown
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40 degrees highest latitude: 90-latitude+23.5 lowest latitude: 90-latitude-23.5
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path of moon
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new moon-waning-full moon-waxing
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true or false: all light travels at same speed
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true
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what is the electromagnetic spectrum
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range of all wavelengths of light
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how was the moon formed
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large collision between earth and mars-sized protoplanet
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how was the solar system formed
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accretion disk and dust formed around sun
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what is the only important parameter for determining a main sequence star?
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mass
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high mass stars
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high luminosity, hot, short lived, large, blue
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low mass stars
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low luminosity, cool, long lived, smaller, red
