ASTRO FINAL 2/3

-The energy transfer process that operates in the Sun via has motion is known as.. A) convection. B) radiation. C) thermonuclear fusion. D) conduction.

a

-The vibrations of the Sun reveal information about... A) the interior structure of the Sun. B) the structure of the atmosphere of the Sun. C) the magnetic field of the Sun. D) the temperature of the core of the Sun. E) the production of energy in the Sun.

a

-Where in the Sun do fusion reactions happen? A) Only the core B) Core and radiation zone C) Everywhere inside the Sun

a

-Which of the following quantities is equal to the energy per second generated by the Sun's nuclear reactions? A) The luminosity of the Sun's photosphere B) The force of gravity holding the Sun together C) The temperature at the Sun's photosphere D) The temperature of the Sun's core

a

-Which of these are not associated with the magneticaly active Sun? A) granulation B) sunspots C) prominences D) aurora E) solar flares

a

-Why does the star Bellatrix in Orion looks bluish to the naked eye? A) The spectrum of light emitted from Bellatrix peaks in the uv region of the spectrum. Within the visible part of the spectrum, there is more emission in the blue than in any other color. B) Bellatrix is moving toward Earth rapidly enough that its light appears appreciably blueshifted. C) Bellatrix is made of blue material.

a

-Light leaving a point source spreads out so that the apparent brightness b of light per unit area varies with distance d according to which of the following laws (∝ means "proportional to")? A) b = constant B) b ∝ 1/d2 C) b ∝ d2 D) b ∝ 1/d

b

-Locate Regulus on the HR diagram on the cover sheet and estimate the luminosity relative to the Sun. If the surface temperature of Regulus is 12,500K and the surface temperature of the Sun is 5800K, determine the radius of Regulus in solar radii. A) 6.4 x 10-8 RSun B) 2.2 RSun C) 4.6 RSun D) Both stars are the same size

b

-On a Hertzsprung-Russell diagram, where would you find stars that are cool and dim? A) lower left B) lower right C) upper right D) upper left

b

-On an H-R diagram, stellar radii ________. A) decrease from left to right B) increase diagonally from the lower left to the upper right C) are greatest in the lower left and least in the upper right D) are impossible to determine

b

-Regulus is at a distance of 24pc and has a radial velocity of 6.1 km/s. Determine the proper motion of Regulus if the space velocity is 28.3 km/s. A) 5.8 arcsec/yr B) 0.24 arcsec/yr C) 801 arcsec/yr D) 27.6 km/s

b

-Stellar parallax is the... A) inferred change in the distance to a star as its light is dimmed by passing through an interstellar cloud. B) apparent shift seen in the position of a nearby star against more distant stars as the Earth orbits the Sun C) difference between the apparent and absolute magnitudes of a star. D) circular or elliptical motion of a star in a binary system as the two stars orbit each other.

b

-Why is the solar corona so much hotter than the photosphere? A) energy is carried upward through the chromosphere by disturbed and tangled magnetic fields B) The corona absorbs light from the photosphere very efficiently. C) The density of the corona is low; following the laws of thermodynamics, the product of density and temperature is a constant. D) Energy is carried upward through the chromosphere by convective gas motions.

a

-assume that in the future, a telescope is built on europa (a moon of jupiter) and measures a parallax of 1.3''. procyon lies about 13 light years distant. what must be the baseline of jupiter's orbit? a) 5.2 au b) 1 au c) 16.9 au

a

-the pattern of rising hot gas cells all over the photosphere is called: a) granulation b) prominences c) filaments d) convective projections e) sunspots

a

-the temp of the corona of the sun is... A) very hot, about 106 K. B) about twice as hot as the photosphere, 12,000 K. C) very cool because it is the farthest part of the Sun from the heat source. D) about the same as that of the photosphere, 5800 K.

a

-How can we characterize the rotation of the Sun? A) differential rotation, with the equator rotating more slowly than the poles B) in a banded pattern, with alternating bands of fast and slow rotation to produce the sunspots C) differential rotation, with the equator rotating faster than the poles D) like a solid body, with all parts rotating at the same rate

c

-How long does the sunspot cycle last, on average? (Ignore the magnetic polarity flip of the Sun) A) between 25 and 35 days B) about 76 years C) about 11 years D) 365.25 days

c

-How many planet Earths could fit inside the Sun? RSun = 109REarth. Volume of a sphere is 4/3πR3. A) about a thousand B) 109 C) about 5 million D) close to a billion

c

-In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass? A) It is transformed into electrons. B) It is recycled back into hydrogen. C) It is converted to energy. D) Conservation of mass dictates no mass can be lost.

c

-Mean temperatures in Europe during the Maunder minimum,when virtually no sunspots were seen between 1645 and 1715, were... A) unchanged, within statistical uncertainty. B) higher than average. C) lower than average.

c

-The Corona of the Sun is superheated and radiates X Rays with a peak wavelength of 0.2nm. Determine the temperature of this region of the Corona. A) 5,800 K B) 3.5 x 10^12 K C) 15 x 10^6 K D) 3 x 10^4 K

c

-The Sun has an absolute magnitude of M=+4.8. How far away would we have to be for the Sun to be just barely visible to the unaided eye (i.e. if m = 6)? A) 1.2 pc B) 6 pc C) 17.4 pc D) 22.4 pc

c

-The Sun's luminosity is 3.83 × 1026 watts. By the time this energy reaches Earth, it has spread out so that it provides only 1370 watts to each square meter. The orbit of Mars has a mean radius of 1.53 AU. How many watts of the Sun's luminosity are provided to each square meter of the surface of Mars? A) 34 B) 153 C) 585 D) 1578

c

-The image shows the star Wolf 359, which has a large proper motion at 0.4 arcsec/year. Determine the transverse velocity of this star if it is at a distance of 2.409pc. A) 0.96 km/s B) 6.02 km/s C) 4.56 km/s D) there is no transverse velocity

c

-The luminosity of a star is.. A) its brightness as seen by people on Earth. B) its brightness if it were at a distance of 10 pc (32.6 ly) from Earth. C) its total energy output per second. D) another name for its color or surface temperature.

c

-The spectral class of the star Enif is K2, while that of the Sun is G2. Which of the following conclusions can be drawn about Enif from this information? A) Enif is intrinsically fainter than the sun B) Enif is intrinsically brighter than the sun C) Enif is cooler than the Sun. D) Enif is hotter than the Sun.

c

-Thermonuclear fusion reactions in the core of the Sun convert four hydrogen atoms in to one helium atom. The helium atom has... A) an undetermined amount of mass, depending on the temperature at which the reaction occurs. B) the same mass as the four hydrogen atoms because the mass of any product has to equal the sum of the mass of its parts. C) less mass than the four hydrogen atoms; the mass loss is converted to energy via the equation E = mc2. D) more mass than the four hydrogen atoms; the energy produced in the reaction appears as the extra mass from the equation E = mc2.

c

-Two stars in our sky have the same apparent brightness. If neither of them is hidden behind gas or dust clouds, then we know that they... A) must be at the same distance from us. B) may be at different distances, in which case the nearer one must have the greater luminosity. C) may be at different distances, in which case the farther one must have the greater luminosity. D) must have the same temperature.

c

-What is the average length of time from one maximum in the number of sunspots on the Sun to the next maximum? A) 22 years B) 7 years C) 11 years D) 4 1⁄2 years

c

-What is thesolar wind? A) The uppermost layer of the Sun, lying just above the corona B) The wind that causes huge arcs of gas to rise above the Sun's surface C) A stream of charged particles flowing outward from the surface of the Sun D) The strong wind that blows sunspots around on the surface of the Sun

c

-a loop of gas and charged particles following the magnetic field lines between sunspots' poles is... a) a colonial mass ejection b) a coronal hole c) a prominence/ filiment d) a ray e) a flare

c

-spectral lines observed in the granules seen at the center of the sun's disk are... A) always redshifted because granules are caused by gas descending into the Sun from higher layers. B) redshifted near the center of the granule and blueshifted near the edge of the granule. C) blueshifted near the center of the granule and redshifted near the edge of the granule.

c

-star A and star B both have an apparent magnitude of 2.0, but star A has an absolute magnitude of +3.0 and star B has an absolute magnitude of -5.0. which statement below is correct? a) star B appears brighter than star A, but actually star B and star A are the same brightness b) star A and star B appear to have the same brightness but actually star A is brighter than star B c) star A and star B appear to have the same brightness, but actually star B is brighter than star A d) star A appears brighter than star B, but actually star B and star A are the same brightness e) it is impossible to determine how bright these stars are or appear to be relative to one another, given the info above

c

For this question, see the parallax equation on the cover sheet for the baseline of Pluto's orbit. The semimajor axis of Pluto's orbit is almost 40 AU. The smallest parallax angle we can measure from orbiting observatories is about 0.001 arcsec. Suppose we use this technique to measure parallax from Pluto's orbit (over the course of half a Pluto "year"). What is the maximum distance we could measure? A) 40 pc B) 1000 pc C) 40,000 pc D) 80,000 pc

c

In the Hertzsprung-Russell diagram on the cover sheet of the exam,which of the following lists is the correct sequence of stars in order of increasing temperature? A) Sirius B, Deneb, Procyon B, the Sun B) Deneb, the Sun, Sirius B, Procyon B C) Sun, Procyon B, Deneb, Sirius B D) Procyon B, Sirius B, the Sun, Deneb

c

The following expressions are parameters of stars that astronomers obtained from their measurements. Which of these conclusions is NOT correct, based on the positions of these stars on the Hertzsprung-Russell diagram on the cover sheet of this exam? (Ls and Rs are the luminosity and radius of the Sun, respectively.) A) luminosity = Ls, radius = Rs, temperature = 6000 K; conclusion: main- sequence star B) luminosity = 104 Ls, radius = 100 Rs, temperature = 5000 K; conclusion: red giant star C) luminosity = Ls, radius = 1/10 Rs, temperature = 20,000 K; conclusion: white dwarf star D) luminosity =1/100 Ls, radius =1/100 Rs, temperature =20,000 K; conclusion: white dwarf star

c

-When two stars of unequal mass orbit each other under their mutual gravitational attraction, where is the center of mass of the system located? A) point halfway between the centers of the stars B) point between the stars, closer to the less massive star C) center of the more massive star D) point between the two stars, closer to the more massive sta

d

-Where on the Hertzsprung-Russell diagram do most local stars in our universe congregate? A) white dwarf area, the "graveyard" of stars B) supergiant area, where the most massive stars spend a significant time C) giant area, where most stars spend the longest time of their lives D) main sequence, where stars are generating energy by fusion reactions

d

-Which of the following correctly states the relationship between the apparent brightness, luminosity, and distance of a star? A) apparent brightness = luminosity × 4π × (distance) 2 B) luminosity = apparent brightness / 4π x (distance)2 C) distance = luminosity / 4π x (apparent brightness)2 D) apparent brightness = luminosity / 4π x (distance)2

d

-Which two fundamental parameters are most often used to place a particular star on a Hertzprung-Russell Diagram? A) apparent magnitude and distance B) apparent magnitude and temperature C) luminosity and distance D) luminosity and temperature

d

-which of the following is the best answer to the question, "why does the sun shine?" a) the sun initially began generating energy through nuclear fusion as it formed, but today it generates energy primarily through the sunspot cycle b) as the sun was forming, nuclear fusion reactions in the shrinking clouds of gas slowly became stronger and stronger, until the sun reached its current luminosity c) the sun initially began making energy through chemical reactions. these heated the interior enough to allow gravitational contraction and nuclear fusion to occur d) as the sun was forming, gravitational contraction increased the sun's temperature until the core became hot enough for nuclear fusion, which ever since has generated the heat that makes the sun shine

d

-which of the following statements about apparent and absolute magnitude is true? A) A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. B) A star with an apparent magnitude of 1 appears brighter than a star with an apparent magnitude of 2. C) The absolute magnitude of a star is another measure of its luminosity. D) All of the above are true.

d

Apparent magnitude is a measure of a star's.. A) Luminosity B) size. C) temperature. D) brightness, as seen from Earth.

d

-In a spectroscopic binary system, the star showing the larger blue shift is: A) hotter and receding faster. B) less massive of the pair and receding slower. C) more massive and approaching us. D) cooler and receding the fastest. E) less massive and approaching us at this moment.

e

-In the previous question, one star is exhiting a blue shift, the other is exhibiting a redshift. If the ratio of speeds is 4:1 this imples the ratio of distances from the center of mass is also 4:1. The smaller star is 8 Solar Masses. Determine the period of revolution of the system if the larger star is 20 AU from the center of the system. A) 25,000 years. B) 200 years. C) 14 years. D) 1 year. E) 158 years.

e

-Star A and star B have the same temperature, but star B is 20 times smaller than star A. Which statement below is correct? A) Star A is bluer and dimmer than star B. B) Star A is redder and dimmer than star B. C) Star A is redder and brighter than star B. D) Star A is redder and brighter than star B. E) Star A and star B have the same color, but star A is brighter.

e

-the doppler shift of the dark regions is 0.001% the speed of light. if one particular spectral line has a rest wavelength of 480.00nm, what is the measured wavelength of the same line from the diagram? a) 0.48 nm b) 479.42 nm c) 300,000 nm d) 480.00 nm e) 480.48 nm

e

True/False The Sun's magnetic field extends throughout the solar system.

true

True/False: -1.5 magnitude Sirius appears 25 times brighter than second magnitude Polaris.

true

True/False: A star of the Sun's diameter, but five times hotter, must be 625 times more luminous than the Sun.

true

True/False: At very large distances from the Sun, its corona turns into the solar wind.

true

True/False: If the distance between us and a star is increased by a factor of 5, the apparent brightness is decreased by a factor of 25.

true

True/False: In a binary system, the less massive stars always remain farther from the center of mass and move faster.

true

True/False: In the proton-proton cycle, 0.007% of the mass ends up as energy, not helium.

true

True/False: In the proton-proton cycle, you must first make deuterium, then helium.

true

True/False: Spectral type, surface temperature, and color all describe the same basic characteristic of a star.

true

True/False: The photosphere of the Sun is about 100 times the diameter of Earth and large sunspots can be larger than our whole planet.

true

-A star of apparent magnitude +5 appears_____than a star of apparent magnitude 3+... A) fainter B) farther away C) brighter D) either brighter or fainter, depending on the distance to the stars

a

-Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 127 hours the star becomes dimmer for about 4 hours. The most likely explanation is that... A) the star is a member of an eclipsing binary star system. B) the star is periodically ejecting gas into space, every 73 hours. C) the star is a Cepheid variable. D) the star is a white dwarf.

a

-Sunspots appear dark because they... A) are cooler than the surrounding surface. B) are regions from which the light is prevented from escaping by strong magnetic fields. C) have a different chemical composition than the surrounding surface.

a

-Sunspots are.. A) cooler, darker regions on the Sun's surface. B) the shadows of cool, dark clouds of matter hanging above the solar surface. C) cooler regions of the Sun's high corona. D) hotter, deeper regions in the Sun's atmosphere.

a

-procyon lies about 13 light years distant, thus its parallax is about: a) 0.40'' b) 0.25'' c) 0.01'' d) 1.3'' e) 0.65''

-b -d=1/p -4p=1 -p=1/4 -p=0.25''

- If Star A is closer to us than Star B, then Star A'sparallax angle is A) hotter than that of Star B. B) larger than that of Star B. C) fewer parsecs than that of Star B. D) smaller than that of Star B.

b

-A particular star has an angle of parallax of 0.1 arc second. What is the distance to this star in light years? A) about 10 ly B) about 33 ly C) about 0.1 ly D) about 3.3 ly

b

-A particular star in a binary star system orbits the other with an average orbital radius of 3 AU and a period of 5 years. What is the sum of the masses of the two stars in the system in solar masses? A) 0.9 B) 1.1 C) 13.9 D) 0.07

b

-All but one of the following statements describe why scientists doubt the solar sunspot cycle affects global climate. Identify which statement is irrelevant to the explanation. A) The solar cycle varies every 11 years; average Earth temperatures do not show an 11 year variation. B) Solar winds can affect satellite communications. C) Variations in solar activity affect the Sun's luminosity by a very tiny amount. D) The variations in solar particle winds do not change the temperature of the Earth's ocean or ground.

b

-An O-star has a hotter surface temperature than the Sun. Therefore, compared to the Sun... A) it emits at about the same wavelengths as the Sun (similar peak) but it is much fainter. B) its emission peaks in the blue part of the spectrum. C) it emits at about the same wavelengths as the Sun (similar peak) but it is much brighter. D) its emission peaks in the infrared part of the spectrum.

b

-If the Sun-Earth separation was 10 AU instead of 1 AU, what would the flux of sunlight (energy per second per square meter) be at the Earth, compared to what it is today? A) 10 times more B) 100 times less C) 10 times less D) About 3.16 (or the square root of 10) times less E) 100 times more

b

-If the temperature of the solar surface is 5800K and Wien's law for the peak wavelength of the spectrum of the Sun, assumed to be a blackbody, is given by λmax T = 2.9 × 106, with T in Kelvins and λ in nanometers (nm), what is the expected dominant wavelength of the Sun? A) 600nm B) 500nm C) 300nm D) 50nm

b

-The Stefan-Boltzmann law indicates that the energy emitted per second per area of an emitting surface varies with the fourth power of the Kelvin temperature. Suppose the center of a sunspot on the Sun's photosphere is 4000 K and the normal photosphere is about 6000 K. About how much energy is emitted each second from each unit area in the center of this sunspot compared with that from the normal photosphere? Assume equal areas A) 100% B) 20% C) 67% D) 98%

b

-The star Hadar is classified as B1 II, which means that it is a... A) cool supergiant B) hot, bright giant. C) cool giant. D) hot supergiant

b

-Two stars in a binary system have a combined mass of 12 solar masses (which was determined by measurements of a = 10.62AU and p = 10 yrs ). If one star is 5 times further from the center of mass than the other, what are the individual masses in solar masses? A) 6 & 6 B) 10 & 2 C) 4 & 8 D) 11 & 1

b

-a computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (its even "on sale"!) why do you turn down his excellent offer? a) solar neutrinos are generated by solar winds, but we're in a solar minimum now, so the risk of damage is very low b) neutrinos rarely, if ever, interact with matter, even your computer c) theres no such thing as a solar neutrino d) the earths natural magnetic field already offers excellent protection against the onslaught of solar neutrinos

b

-which of the following stellar properties has the greatest range in values? a) radius b) luminosity c) surface temperature

b

- Which of the following is not a characteristic of the 11-year sunspot cycle? A) The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous. B) The likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common. C) The sunspot cycle is very steady, so that each 11-year cycle is identical to every other 11-year cycle. D) The Sun's entire magnetic field flip-flops with each cycle, so that the overall magnetic cycle averages 22 years.

c

-By approximately how many times dimmer is the star Sirius (m=-1.7) than the full Moon (m = -13) in our sky? A) 11 times dimmer B) 2.512 times dimmer C) 33,000 times dimmer

c

-Galileo observed the phenomenon of solar rotation in the early 1600s by... A) noting the periodic (monthly) variation of auroral disturbances, or northern lights. B) watching bright regions of hydrogen gas drift across the Sun. C) measuring the motion of sunspots across the solar surface. D) measuring the Doppler shift of hydrogen spectral lines from the east and west limbs of the Sun.

c

- A star has an apparent magnitude of +7 and an absolute magnitude of -4. What is the distance to the star? A) 2.5 x 106pc B) 25,100 pc C) 10 pc D) 1585 pc E) 0.00004pc

d

-A star's absolute magnitude and its apparent magnitude have the same numerical value. How far is this star from Earth? A) It is not possible for a star to have the same absolute and apparent magnitudes. B) The star would have to be an infinite distance away. C) 10 ly D) 10 pc

d

-Consider HR diagram ONE on the cover sheet. Find Capella and the Sun. Estimate how many times bigger or smaller Capella is than the Sun. A) between 90 and 100 times smaller B) between 90 and 100 times bigger C) between 9 and 10 times smaller D) between 9 and 10 times bigger E) both stars are the same size

d

-Consider the Hertzsprung-Russell diagram on the cover sheet of the exam, which of the following lists is the correct sequence of stars in order of increasing intrinsic brightness? A) Deneb, the Sun, Sirius B, Procyon B B) Sirius B, Deneb, Procyon B, the Sun C) Sun, Procyon B, Deneb, Sirius B D) Procyon B, Sirius B, the Sun, Deneb

d

-Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant? A) Spectral type M1, luminosity class V B) Spectral type G2, luminosity class V C) Spectral type O9, luminosity class I D) Spectral type M2, luminosity class I

d

-Hydrostatic equilibrium in our Sun is the balance between.. A) convection and gravitation. B) radiation and gravitation. C) convection and radiation. D) gravitation and pressure. E) pressure and radiation.

d

-In order to turn a star's proper motion into its space velocity, we must also know: A) its spectral type and period of rotation. B) its distance and mass. C) its temperature and age. D) its distance and radial velocity. E) its mass and spectral type.

d

-Our Sun is a star of spectral type ________. A) S B) M C) F D) G

d

-Spectral types of stars (e.g.,O,B,A,F,G,K,andM) uniquely define their... A) sizes or radii. B) absolute magnitudes. C) luminosities. D) surface temperatures.

d

-The Sun's surface, as we see it with our eyes, is called the... A) corona. B) core. C) chromosphere. D) photosphere.

d

-The axes on a Hertzsprung-Russell (H-R) diagram typically represent ________. A) mass and luminosity B) luminosity and apparent brightness C) mass and radius D) luminosity and surface temperature

d

-The granular appearance of the surface of the Sun is evidence of what phenomenon occurring in or on the Sun? A) cells of thermonuclear fusion just under the visible surface B) rapid rotation of the surface layers producing swirls of gas C) concentration and heating of ionized gas by regions of high magnetic fields D) convective motion under the solar surface

d

-The primary source of the Sun's energy is... A) dark energy. B) the weak force creating energy from uranium decay. C) oxidation of carbon in the core. D) the strong force fusing hydrogen into helium. E) gravitational collapse of the helium coreward.

d

-The spectral sequence in order of decreasing temperature is A) BAGFKMO. B) ABFGKMO. C) OBAGFKM. D) OBAFGKM. E) OFBAGKM.

d

-The star shown is Rigel, from the constellation Orion. If the Earth orbited Rigel at 1AU, it would be seen as a very large blue star with an apparent magnitude of -38!! Rigel actually has an apparent magnitude of +0.2. If the distance to rigel is 772.9 ly (237.1pc), determine the absolute magnitude of Rigel. A) -44.9 B) +6.7 C) -9.2 D) -6.7

d

-The typical speed of spicular material traveling outward from the photosphere in the direction of Earth is 20 km/s. What would be the observed wavelength of the Balmer Hα hydrogen spectral line (656nm) emitted by this gas compared with that from stationary solar material? A) There will be no shift since the light is emitted by hydrogen gas in both the spicule and the stationary solar material. B) 656.044 nm C) 0.000067 nm shorter than the Hα from the stationary solar material D) 655.956nm

d

-Using the HR Diagrams on the cover sheet, determine which of the following lists is the correct sequence of stars in order of increasing size, or stellar radius. A) Sirius B, the Sun, Betelgeuse, Mira B) Mira, Betelguese, the Sun, Sirius B C) Betelgeuse, Mira, the Sun, Sirius B D) Sirius B, the Sun, Mira, Betelgeuse

d

-What term is given to the visible "surface" of the Sun? A) prominence B) corona C) chromosphere D) photosphere

d

True/False: The solar corona is much cooler than the Sun's surface, hence we must wait for a solar eclipse to glimpse it with the naked eye.

false

True/False: Two stars have the same luminosity. Star X is spectral type F, while Star Y is spectral type K. Therefore, Star X is larger in radius than Star Y.

false

True/False: When a photon is produced in the core of the Sun, it undergoes a random photon walk that could last hundreds of thousands of years. During this process, the photons remain entirely gamma rays that are eventually radiated into space.

false

True/False: energy from the core of the sun first travels slowly through convection zone and then much faster through the outer radiation zone

false