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63 Cards in this Set
- Front
- Back
Before we can use parallax to measure the distance to a nearby star, we first need to know __________. |
the Earth-Sun distance |
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Which of the following is a valid way of demonstrating parallax for yourself? |
Hold up your hand in front of your face, and alternately close your left and right eyes. |
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What is the cause of stellar parallax? |
Earth's orbit around the Sun. |
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The more distant a star, the __________. |
smaller its parallax angle |
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Approximately what is the parallax angle of a star that is 20 light-years away? |
0.16 arcsecond d(in light years)=3.26 X 1/p(in arcseconds) |
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Suppose that a star had a parallax angle of exactly 1 arcsecond. Approximately how far away would it be, in light-years? |
3.3 light-years |
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The total amount of power (in watts, for example) that a star radiates into space is called its _________. |
luminosity |
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According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples? |
Its apparent brightness will decrease by a factor of 9. |
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Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do? |
Calculate the star's luminosity if we know its distance, or calculate its distance if we know its luminosity. |
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If star A is closer to us than star B, then Star A's parallax angle is _________. |
larger than that of Star B |
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What do we need to measure in order to determine a star's luminosity? |
apparent brightness and distance |
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If the star Alpha Centauri were moved to a distance 10 times farther than it is now, its parallax angle would |
get smaller. |
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We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them. |
Far left: gamma rays, x rays, ultraviolet, visible light, infrared, radio waves :Far Right Visible light spans only a very narrow range of wavelengths, from about400 nanometers at the blue (violet) end to about 700 nanometers at the red end. |
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Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them. |
Far Left: Radio Waves, infrared, visible light, ultraviolet, x rays, gamma rays :Far Right Because the speed of light is a constant, longer wavelengths must mean lower frequencies, and vice versa |
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Rank the forms of light from left to right in order of increasing energy. To rank items as equivalent, overlap them. |
Far Left: radio waves, infrared, visible light, ultraviolet, x rays, gamma rays :Far Right the energy of a photon of light is proportional to its frequency |
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Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them. |
all forms of light travel at the same speed, regardless of wavelength, frequency, or energy. |
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A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is: |
redshifted. |
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The diagrams below each show the motion of a distant star relative to Earth (not to scale). The red arrows indicate the speed and direction of the star’s motion: Longer arrows mean faster speed. Rank the stars based on the Doppler shift that we would detect on Earth, from largest blueshift, through no shift, to largest redshift. |
blueshift: longest arrow pointing towards Earth, shorter arrow pointing towards Earth, arrow pointing down and away from Earth, shorter arrow pointing up and away from Earth, longer arrow pointing up and away from Earth :redshift the star moving fastest toward Earth will have the greatest blueshift, the star moving across our line of sight will have no shift at all, and the star moving fastest away from us will have the greatest redshift. |
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Each diagram below shows a pair of spectra with a set of spectral lines. The top spectrum always shows the lines as they appear in a spectrum created in a laboratory on Earth (“Lab”) and the bottom spectrum shows the same set of lines from a distant star. The left (blue/violet) end of each spectrum corresponds to shorter wavelengths and the right (red) end to longer wavelengths. Rank the five stars based on the Doppler shifts of their spectra, from largest blueshift, through no shift, to largest redshift. |
lines that are shifted to the left (toward the blue/violet) compared to the laboratory spectrum represent blue shifts, and lines shifted to the right (toward the red) represent redshifts. |
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An important line of hydrogen occurs at a rest wavelength (as measured in a laboratory) of 656 nm (a nanometer (nm) is a billionth of a meter). Each diagram below has this line labeled with its wavelength in the spectrum of a distant star. Rank the motion of the stars along our line of sight (radial motion) based on their speed and direction, from moving fastest toward Earth, through zero (not moving toward or away from Earth), to moving fastest away from Earth. |
toward Earth: 646 nm, 650 nm, 656 nm, 657 nm, 663 nm :Away from Earth This ranks the stars in wavelength order. The first two stars are moving toward us, because their lines have wavelength shorter than the rest wavelength of 656 nm. The last two stars are moving away from us, because their lines have wavelength longer than the rest wavelength of 656 nm. |
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All stars spend approximately the same amount of time on the main sequence. |
false |
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Most stars on the main sequence fuse hydrogen into helium in their cores, but some do not. |
false |
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Blue stars are always more luminous than red stars |
false |
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Two stars both lie on the main sequence. Star X is spectral type A, while Star Y is spectral type G. Star X must be more massive than Star Y. |
true |
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Two stars have the same spectral type. Star X is in luminosity class III, while Star Y is in luminosity class V. Star X must be larger in radius than Star Y. |
true |
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The approximate main-sequence lifetime of a star of spectral type O is ________. |
3 million years |
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The figure shows a standard Hertzsprung-Russell (H-R) diagram. Label the horizontal and vertical axes using the two blanks nearest the center of each axis, and label the extremes on the two axes using the blanks on the ends of the axes. |
top to bottom: brighter, luminosity, fainter left to right: hotter, surface temperature, colder |
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Use the labels to identify what kinds of stars inhabit each region of the the H-R diagram. |
top to bottom: supergiants, main sequence, red giants, main sequence, white dwarfs |
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The diagonal lines on the H-R diagram represent lines along which all stars would have the same radius. Label the three white lines with the correct values for the radii of stars that fall on them. |
top to bottom: 1000 solar radii, 1 solar radius, 1 Earth radius Stellar radii increase diagonally on the H-R diagram from the lower left to the upper right. |
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The position of a star along the main sequence tells you both its mass and its hydrogen-burning lifetime. Label the indicated blanks on the main sequence with the approximate lifetimes of stars at those positions. |
top to bottom: 10 million year lifetime, 10 billion year lifetime, 100 billion year lifetime Stars spend most of their lives on the main sequence, where they generate energy by fusing hydrogen into helium in their cores. High-luminosity stars have much shorter main-sequence lifetimes than lower luminosity stars, because they burn through their supply of hydrogen at a much faster rate |
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Listed following are several fictitious stars with their luminosities given in terms of the Sun’s luminosity (LSun) and their distances from Earth given in light-years (ly). Rank the stars based on how bright each would appear in the sky as seen from Earth, from brightest to dimmest. If two (or more) stars have the same brightness in the sky, show this equality by dragging one star on top of the other(s). |
Brightest: Nismo, Shelby and Ferdinand overlap, Enzo, Lotus :Dimmest |
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Listed following is the same set of fictitious stars given in Part A. Rank the stars based on how bright each would appear in the sky as seen from Jupiter, from brightest to dimmest. |
Brightest: Nismo, Shelby and Ferdinand overlap, Enzo, Lotus :Dimmest Stars are so far away that any difference in distance to the stars from Earth and Jupiter is negligible. As a result, the answer to this part is the same as the answer to Part A. |
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The following figure shows how four identical stars appear in the night sky seen from Earth. The shading is used to indicate how bright (white) or dim (dark gray) the star would appear in the sky from Earth. Rank the stars based on their distance from Earth, from farthest to closest. |
left to right: The darkest to the left and brightest to the right apparent brightness decreases with distance |
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Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is __________. |
less luminous, cooler, smaller, and less massive |
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Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________. |
cooler and larger in radius |
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Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________. |
hotter and smaller in radius |
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Listed following is a set of statements describing individual stars or characteristics of stars. Match these to the appropriate object category. |
red giant or supergiant: very cool but very luminous, found in the upper right of the H-R diagram Main sequence: the sun for example, the majority of stars in our galaxy, the hottest and most luminous white dwarfs: not much larger in radius than earth, very hot but very dim |
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Binary Stars |
consists of 2 stars orbiting their common center mass |
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Majority of Stars in our Galaxy are... |
Binary Stars Big Dipper (Mizar) |
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Hipparcos Telescope |
precise distant measurement by parallax could map the height of astronaut on moon |
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Kepler Telescope |
small slice of Milky way variations in light of nearby stars looking for exoplanets designed to notice light curves in stars |
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Gaia Telescope |
devoted to angular position Similar to Hipparcos Map width of a button of man on moon |
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ASTRO |
devoted to star angular position measurements |
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The Kepler Spacecraft searched for exoplanets in this way? |
Finding dips in parent star's light curve |
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The Kepler team found that multiple exoplanet systems are? |
Relatively common, hundreds found |
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Gaia can get a measurement of a star's true angular position by? |
Getting a new position measurement every year |
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How many parsecs is the distance to 61 Cygni? |
3.18 parsecs D=1/0.314=3.18pc |
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61 Cygni is 3.18 pc away from Earth. How many LY is that? |
10.4 LY 3.14 x 3.26=10.4 |
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If a stars apparent magnitude m is less than its absolute magnitude M then? |
the star is closer than 10pc |
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Low magnitude |
Brighter |
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Higher magnitude |
Dimmer |
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This star is brighter than the others if viewed from Earth? |
Vega |
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This star is intrinsically brighter than the others? |
Antares |
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Spectral Type order |
OBAFGKM |
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What is it's surface Temperature if max=834nm. maxT=0.0028977mK |
T=3474 |
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Betelguese |
cooler the sun red supergiant mass= 7.7 |
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Color reveals |
surface temperature |
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Luminosity reveals |
total energy output |
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Every sq meter of red star surface has the same luminosity owing to the Stefan-Boltzman law |
joules/sec __________ m^2=6T^4 |
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You have one sq meter of the surface of a red M-class star and a sq meter of the surface of a blue O-type star. Which sq meter produces more energy per sec? |
O-class |
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Why does it's sq meter produce more joules of energy per second? |
temperature |
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How do you interpret a star in the upper right of the H-R diagram: red, spectral type M, very luminous |
Its diameter is larger than the main seq M-type stars Bigger=Brighter |
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UBV band |
Star brighter in B band than V band U=384nm B=442nm V=540nm |