Exam 3 Review Flashcards
(33 cards)
Light leaving a point source spreads out so that the apparent brightness, b varies with distance d according to which of the following laws? (∝ means "proportional to.") A) b ∝ 1/d B) b ∝ 1/d2 C) b = constant D) b ∝ d2
B) b ∝ 1/d2
Parallax is the:
A) distance to an object, measured in parsecs.
B) angle subtended by an object, as see by us.
C) apparent shift in position of a nearby object as we move.
D) shift in position of an object as it moves.
C) apparent shift in position of a nearby object as we move.
The luminosity of a star is:
A) another name for its temperature.
B) its brightness as seen by people on Earth.
C) its total energy output over all wavelengths.
D) another name for its size.
C) its total energy output over all wavelengths.
What does apparent brightness tell us about a star?
A) Its size compared to the Sun.
B) The intrinsic brightness of a star.
C) The brightness of a star as it appears in our sky.
D) The brightness the star would appear to have if it were exactly 10 parsec from the Earth.
C) The brightness of a star as it appears in our sky.
The spectral type of a star is most directly related to (and determines uniquely) its: A) size or radius B) absolute magnitude C) luminosity D) surface temperature
D) surface temperature
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) may be at different distances, in which case the nearest one must have the greater luminosity.
B) must have formed from the same star cluster.
C) may be at different distances, in which case the farther one must have the greater luminosity.
D) may be cousins to one another.
C) may be at different distances, in which case the farther one must have the greater luminosity.
The spectral type of the Sun is G2 and the star Enif is K2. From the information, we know that Enif is:
A) intrinsically fainter than the Sun.
B) cooler than the Sun
C) intrinsically brighter than the Sun.
D) hotter than the Sun.
E) A & B
E) A & B
Where on the Hertzsprung-Russell diagram do most local stars in our universe congregate?
A) In the supergiant area, where most massive stars spend significant time.
B) In the giant area, where most stars spend the longest time of their lives.
C) In the white dwarf area, the “graveyard” of stars.
D) On the main sequence where stars generate energy by hydrogen burning.
D) On the main sequence where stars generate energy by hydrogen burning.
Compared to a star in the middle of the diagram, a star in the lower left part of the Hertzsprung-Russell diagram is: A) brighter. B) larger. C) cooler. D) smaller.
D) smaller.
Which important stellar parameter can be determined by the study of binary stars? A) The age of the stars. B) Stellar masses. C) Surface temperature of the stars. D) The distance of the stars from Earth
B) Stellar masses.
Where do we find the most massive stars on the main sequence in a Hertzsprung-Russell diagram?
A) Upper left.
B) They all have approximately the same mass, because this is what defines the main sequence.
C) Lower right.
D) Center, with lower mass stars on either side.
A) Upper left.
Spectroscopic parallax is the:
A) apparent change in position of the absorption lines in a star’s spectrum due to the Doppler shift, caused by Earth’s motion around the Sun.
B) apparent change in position of a nearby star compared to distant background stars, due to the motion of Earth around the Sun.
C) apparent change in position of the absorption lines in a star’s spectrum due to the Doppler shift, caused by the star’s motion around the center of mass in a binary star system.
D) distance to a star measured using the spectral type and luminosity class.
D) distance to a star measured using the spectral type and luminosity class.
What is the difference between an optical double star and a visual binary star?
A) There is no difference — they are two names for the same thing.
B) Optical double stars can be seen as separate stars only through a telescope, whereas visual binaries can be seen with the unaided eye.
C) An optical double is an illusion. The stars are at vast distances from each other and are not actually orbiting each other, whereas in a visual binary, the stars are actually orbiting each other.
D) The stars in an optical double star are actually orbiting each other, whereas a visual binary is an illusion — the stars are at vast distances from each other and are not actually orbiting each other.
C) An optical double is an illusion. The stars are at vast distances from each other and are not actually orbiting each other, whereas in a visual binary, the stars are actually orbiting each other.
A simple relationship exists between mass and luminosity for: A) all stars. B) main sequence stars. C) giant stars. D) supergiant stars and white dwarfs.
B) main sequence stars.
The mechanism at work when energy is transmitted by convection is:
A) the successive exchange of energy between atoms.
B) the passage of radiation through a gas.
C) the mass motion of hot gases.
D) the countless interactions of photons.
C) the mass motion of hot gases.
The neutrino is:
A) an uncharged nuclear particle with mass intermediate between those of the electron and the proton.
B) another name for an electron that carries a positive charge instead of negative charge.
C) an elusive, subatomic particle having little or no mass and no charge, and very difficult to detect.
D) a heavy, uncharged nuclear particle, easily detected.
C) an elusive, subatomic particle having little or no mass and no charge, and very difficult to detect.
What name is given to the visible "surface" of the Sun? A) Corona B) Chromosphere C) Photosphere D) Prominence
C) Photosphere
The granulation pattern seen on the visible “surface” of the Sun is indicative of:
A) convection of gas in the region under the surface.
B) heating of the Sun’s atmosphere by solar flares.
C) the differential rotation of the Sun.
D) strong magnetic fields cooling the gas in certain regions.
A) convection of gas in the region under the surface.
The center of the granular cells on the surface of the Sun are brighter than the edges of the cells because:
A) the centers are composed of different gases than the edges.
B) the centers are hotter than the edges.
C) the centers are devoid of any matter.
D) the centers are cooler than the edges.
B) the centers are hotter than the edges.
The technique used to obtain the direct information about the internal structure of the Sun is: A) helioseismology. B) spectroscopy. C) neutrinos. D) Newton’s law of gravitation.
A) helioseismology.
Sunspots appear dark because they:
A) are shadows on the surface of the Sun caused by planets.
B) are cooler than surrounding regions.
C) are regions from which the light is prevented from escaping by strong magnetic field.
D) have a different chemical composition than the surrounding surface.
B) are cooler than surrounding regions.
Which of the following methods is not used to transport energy from the core to the surface of the Sun?
A) Radiation
B) Convection
C) Conduction
D) All of the above are important in the solar interior.
C) Conduction
The chromosphere appears red because:
A) it is hotter than the photosphere.
B) as the Sun rotates, the chromosphere appears to move away from us radially.
C) it has a higher concentration of heavy metals.
D) its spectrum is dominated by hydrogen emission.
D) its spectrum is dominated by hydrogen emission.
The space between stars is now known to contain:
A) large quantities of dust that absorb light but no gas, either atomic or molecular.
B) gas, made up of atoms, molecules, and dust particles.
C) a perfect vacuum.
D) variable amounts of gas but no dust, because dust forms only in planetary systems near stars.
B) gas, made up of atoms, molecules, and dust particles.
