astr exam 2

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Binghamton University *

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114

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Astronomy

Date

Oct 30, 2023

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pdf

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Uploaded by EarlElement2068

1.What term is given to the visible "surface" of the Sun? D) photosphere 2.-spectral lines observed in the granules seen at the center of the sun's disk are... C) blueshifted near the center of the granule and redshifted near the edge of the granule. 3. The temp of the corona of the sun is... A) very hot, about 106 K. 4.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? D) 655.956nm 5. 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 B) 20% 6.-Sunspots are.. A) cooler, darker regions on the Sun's surface. 7.-What is the average length of time from one maximum in the number of sunspots on the Sun to the next maximum? C) 11 years 8.-Galileo observed the phenomenon of solar rotation in the early 1600s by... C) measuring the motion of sunspots across the solar surface. 9.-Mean temperatures in Europe during the Maunder minimum,when virtually no sunspots were seen between 1645 and 1715, were... C) lower than average. 10.-Thermonuclear fusion reactions in the core of the Sun convert four hydrogen atoms in to one helium atom. The helium atom has... C) less mass than the four hydrogen atoms; the mass loss is converted to energy via the equation E = mc2. 11.-The energy transfer process that operates in the Sun via has motion is known as.. A) convection. 12.-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? B) 500nm 13.-The granular appearance of the surface of the Sun is evidence of what phenomenon occurring in or on the Sun? D) convective motion under the solar surface 14.-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 15.-Sunspots appear dark because they... A) are cooler than the surrounding surface. 16.-How can we characterize the rotation of the Sun? C) differential rotation, with the equator rotating faster than the poles 17.At very large distances from the Sun, its corona turns into the solar wind. true 18.The photosphere of the Sun is about 100 times the diameter of Earth and large sunspots can be larger than our whole planet. true 19.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 20.The Sun's magnetic field extends throughout the solar system. true 21.In the proton-proton cycle, 0.007% of the mass ends up as energy, not helium. true 22.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 23.-Stellar parallax is the... B) apparent shift seen in the position of a nearby star against more distant stars as the Earth orbits the Sun 24.-A particular star has an angle of parallax of 0.1 arc second. What is the distance to this star in light years? B) about 33 ly 25.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? C) 40,000 pc 26.Apparent magnitude is a measure of a star's.. D) brightness, as seen from Earth. 27.-A star of apparent magnitude +5 appears_____than a star of apparent magnitude 3+... A) fainter 28.-By approximately how many times dimmer is the star Sirius (m=-1.7) than the full Moon (m = -13) in our sky?

C) 33,000 times dimmer 29.-A star's absolute magnitude and its apparent magnitude have the same numerical value. How far is this star from Earth? D) 10 pc 30.-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")? B) b ∝ 1/d2 31.-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? C) 585 32.-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)? C) 17.4 pc 33.-The luminosity of a star is.. C) its total energy output per second. 34.-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... C) may be at different distances, in which case the farther one must have the greater luminosity. 35.-Which two fundamental parameters are most often used to place a particular star on a Hertzprung-Russell Diagram? D) luminosity and temperature 36.-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. 37.-Spectral types of stars (e.g.,O,B,A,F,G,K,andM) uniquely define their... D) surface temperatures. 38.-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? C) Enif is cooler than the Sun. 39.-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? D) Procyon B, Sirius B, the Sun, Deneb 40.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? C) Sun, Procyon B, Deneb, Sirius B 41.-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. D) Sirius B, the Sun, Mira, Betelgeuse 42.-Where on the Hertzsprung-Russell diagram do most local stars in our universe congregate? D) main sequence, where stars are generating energy by fusion reactions 43.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.) C) luminosity = Ls, radius = 1/10 Rs, temperature = 20,000 K; conclusion: white dwarf star 44.-The star Hadar is classified as B1 II, which means that it is a... B) hot, bright giant. 45.-When two stars of unequal mass orbit each other under their mutual gravitational attraction, where is the center of mass of the system located? D) point between the two stars, closer to the more massive sta 46.-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? B) 1.1 47.-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? B) 10 & 2 48.-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. C) 4.56 km/s 49.-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. B) 0.24 arcsec/yr 50.-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. B) 2.2 RSun

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