6 Unit If a light source is receding from us we say it has a Red shift. This means the light source will appear red. B. Incorrect.
If a star is moving away from us, its light will be Doppler shifted toward the _______. A. Red
If a star is receding from us the light it emits will be _____.
A. Red shifted.
If a source, emitting light of wavelength L, is approaching us at speed v, and if c is the speed of light; the change in wavelength dL that we will observe is ____. C.. dL / L = v / c. The Doppler effect _____.
A.. Is the change in observed wavelength from a wave source that is approaching or receding from us ..
If two stars have the same spectral class and are of different sizes, they must have different _____. B.. Absolute magnitudes. If two stars of the same spectral class have different absolute magnitudes, they must have different ___. E.. Sizes. The Stefan-Boltzmann law is _____.
A.. The total energy emitted per unit area per unit time is proportional to the fourth power of the temperature in degrees Kelvin.
If two stars of the same spectral class have different absolute magnitudes, they must have different ___. E.. Sizes. The total energy emitted per unit area by a black body is proportional to the ___ power of the Kelvin temperature. C.. Fourth. If a star is approaching us at 0.01 the speed of light and it is emitting 500.0 nm light, we will see a wavelength shift of __. D.. 5.0 nm toward the blue. If a star is receding from us at 0.1 times the speed of light. A 700 nm wavelength light emitted by it will appear as __ nm light to us. D. 770. A galaxy is moving away from us at 0.01 times the speed of light. If a spectral line of 500 nm is emitted from the galaxy, what wavelength will be observed on Earth? C.. 505 nm. If another galaxy was moving toward us at a speed which is 0.1 times the speed of light, the Doppler shift (change in wavelength) of a spectral line of 800 nm would be __ .
B.. 80 nm toward the blue.
These curves show the continuum radiation produced by two stars. Which star has the lower temperature? B.. T1. The perfect radiator with the larger temperature is ____. B.. T2.
Two stars have the same surface area, The first star, S1, has a Kelvin temperature which is two times as high as the second star, S2. Which star is the brighter and by how many times? F.. Star S1 is sixteen times brighter than S2.. The parallax of a star is the angle through which the star appears to move (against the background stars) in the course of a year (corrected for its position relative to the ecliptic). C. Wrong -- half the angle in a year.
In the diagram, which angle is the star's parallax? B. B
The stellar parallax of a star is the angle subtended by the _____ as seen from the star.
radius of the Earth's orbit.
A..
An angular shift in the apparent position of a star due to the Earth's motion about the Sun is termed _________. F. parallax. If the parallax of a star is measured in seconds of arc, the reciprocal of this is the star's distance in __ . C. pc's A possible definition for the parsec is the distance to a star whose parallax is _____ second(s) of arc (corrected for its position relative to the ecliptic). B. 1.0.
Spacecraft have reliably measured the trigonometric parallax of stars to a distance of ____ pc. E.. 100. If a star has a parallax of 1/2 sec of arc its distance is __ pc.
C.. 2. D.. 10.
If a star has a parallax of 0.1 sec of arc, its distance is _____ pc. If a star has a parallax of 2 sec of arc, its distance is ____ pc.
C. 1/2.
If a star has a parallax of 1/5 sec of arc, its distance is __ pc. C.. 5. Which stars have a small positive luminosity?
wavelengths. B.. Intrinsically dim stars. A.. Takes into account radiation at all
The bolometric magnitude is useful because it _____.
Another system that astronomers use to measure luminosity is the ___ system.
magnitude.
D.. absolute
The rate at which a star radiates (expressed in energy units per unit time) is the star's _____. E.. luminosity. Which stars have a large negative luminosity?
D.. No stars.
The magnitude of a star based on all of the electromagnetic energy ideally reaching the earth is called the _____ magnitude. D.. bolometric. Which stars have a small positive luminosity?
C). C.. Green stars. E.. all three (A, B, and
We can get the color (effective) temperature for a star from _______.
Which of the following are among the things that can be learned from a star's spectrum?
E.. all three (A, B, and C).
Stellar diameters can be calculated using ______.
A.. radiation laws and measured luminosity.
Which of the following are among the things that can always be learned from a star's spectrum? D.. both A and B. _____ are often used to determine stellar masses.
B.. Binary stars.
We can get a measure of the relative abundance of elements at the surface of a star by studying the ____. D.. Dark absorption lines. We can get the chemical composition of the surface of a star by studying its _____.
Spectrum. C..
Magnetic fields can cause the spectral lines of atoms to appear broadened and/or split. This is termed ___. E.. The Zeeman effect. Magnetic fields on a star cause _____.
D.. Opacity. B.. Splitting and spreading of spectral lines.
The _____ of a gas is a measure of how far light of a specified wavelength can penetrate. Stellar atmospheric structure is measured by _______.
lines. E. spectra using opacity effects. E.. Doppler spreading of spectral
The rotation of a star can be determined by studying _____. The rotation of a star causes _____.
C.. Doppler spreading.
We can tell if a star has turbulence (atmospheric motion) by _____.
C.. Turbulent broadening.
C. Doppler spreading.
The rapid motion of atoms in a star's photosphere due to its temperature, causes _____. rapid The motion of atoms in a star's photosphere causes _____.
Absorption lines. D. Doppler broadening.
We can get a measure of the pressure in a star's photosphere by examining its ___. C.. Which of the following are among the things that can be learned from a star's spectrum?
D.. both A and B.
We can determine if a circumstellar nebula surrounds a star by observing red and blue shifted emission lines in the stellar spectra. A.. Correct. We can measure the radial velocity of a star from the _____.
lines. A.. Doppler shifts of its spectral
Shells and gases ejected from a star can be detected by studying their _____. The radial velocity of a star is measured by observing its _____.
spectral lines.
E.. B and C.
C. Doppler shift in the
The net Doppler shift of a star's spectral lines can tell us its ___. The radial velocity is usually expressed in units of _____. The tangential velocity of a star is _____.
sight.
B. Radial velocity.
C.. Kilometers per second
C. The star's actual speed at right angles to the line of
The Doppler shift enables us to detect the tangential velocity of a star.
B.. Incorrect.
The proper motion of a star is the star's _____?
B.. Angular motion across the sky. A.. Proper motion. D. Space velocity
The ____ of a star is the star's rate of angular motion across the sky.
The ______ of a body is its true speed & direction relative to the Sun. The space velocity of a star is the star's _____.
Sun
A. True speed & direction of motion relative to the
Proper motion is usually expressed in _____?
B.. Seconds of arc per year or century.
Space velocity is usually expressed in _____? E.. km/s. The letters in the name "H-R diagram" stand for Herman-Russell Small, hot, faint stars, often called degenerate, are termed _____.
B.. Incorrect. D. white dwarfs.
The diagram which plots absolute magnitude versus spectral class is known as the H-R diagram. H-R stands for _____. E.. Hertzsprung-Russell. The majority of stars shown on the H-R diagram are the _______ stars.
C.. main sequence.
Giants are denoted by line _____. C. C. Main sequence stars are denoted by line _____. B. B. Supergiants stars are denoted by line ____. D.. D.
Which line represents the giant region? D.. 4.
The absolute magnitude of the A0 main sequence star is __ . D.. +1.
Of the stars, V, X, Y, Z, which star is the brightest? C. Y.
Of the stars labeled A through E, the brightest of the hotter stars is _____. B.. B.
Of the stars, V, X, Y, Z, which star is intrinsically the dimmest?
D.. Z.
Of the stars labeled A through E, the intrinsically dimmest star _____. A.. A.
Which of the stars is the hottest? A.. A.
Which of the marked stars is the hottest? D.. Z.
Which of the stars is the coolest? E .E
Which of the marked stars is the largest? D. D
Of the stars V, X, Y, and Z, which star is the smallest? D.. Z.
Which of the marked stars (A, B, C, D, & E) is the smallest? A.. A. star apparent magnitude spectrum
a b c d e
15 20 15 8 12
B9 main sequence M3 supergiant G2 main sequence M5 main sequence M2 main sequence
The most apparently bright star in this table is star _____. D.. d. star apparent magnitude a b c d e 15 20 15 15 10 spectrum G2 main sequence M3 supergiant B9 main sequence M5 main sequence M3 main sequence
The hottest star in this table is star _____. C. c. The star in this table which is least luminous is ____. E.. e.
Which of the following is needed to determine the distance to a star using the H-R diagram? G.. all three-A, B, C. We can estimate the size of a star by using the H-R diagram position which gives luminosity. The Stefan-Boltzmann law then gives the size, since the star's ______ is also determined by the H-R diagram. E.. None of the above. On the H-R diagram, a line of constant star radius slants down from left to right.
Correct. A.
The stars within 4 pc of the Sun are called _____ stars.
D. Representative.
Most of the apparently bright stars in the sky are bright because they are close to our Sun. (within 10 pc) D.. Wrong -- they are mostly intrinsically bright and lie far from the Sun.. The stars with an apparent magnitude brighter than first magnitude are called representative stars. B.. Incorrect. There are more red giants and supergiants on the list of prominent stars than are found on the list of representative stars. A. Correct. The radiation pressure in a star tries to make the star _____. The gravitational forces in a star try to make the star _____.
B.. Expand. C.. Contract.
The gas pressure of a star tries to make the star _____. D. Expand. The mass-luminosity relation for main sequence stars is ____:
G.. both A and D
Which of the following is necessary for a star to first reach the main sequence?
generation equals energy losses.
B.. energy
The Russell-Vogt theorem states:
its mass and chemical composition
A.. The equilibrium structure of an ordinary star is determined by
If its apparent magnitude is +5, the distance to the star marked B is ____. B.. 10 pc.
What is the distance to star D if its apparent magnitude is +6 ? B.. Between 10 pc and 100 pc. star apparent magnitude a b c d e 15 3 10 15 7 spectrum G2 main sequence M3 supergiant M3 main sequence B9 main sequence M5 main sequence
The furthest star in this table is ____. D.. d. The closest star in this table is ____. C. c.
The youngest stars, called Population II, have between 1-4% of their mass in elements heavier than helium. B. incorrect -- Called population I. The youngest stars, called Population I, have between 1-4% of their mass in elements heavier than helium. A.. correct. The oldest stars, called Population I, have between 1-4% of their mass in elements heavier than helium. D.. incorrect -- both B and C changes needed.