Suppose two stars with the same luminosity are at different distances from Earth. Which has the greater apparent brightness?
answer
the closer star
The closer the object, the brighter it will appear.
question
What important property of a star do we learn from its spectral class?
answer
temperature
The temperature of a star determines at what wavelengths its atmosphere absorbs photons.
question
Which of the following methods is useful for determining a star's approximate surface temperature?
answer
measuring its apparent brightness through two or more color filters and comparing these values
As few as two brightness measurements at different wavelengths can be used to determine the effective blackbody temperature of a star.
question
Why are we unable to measure parallax shifts for most of the stars in the Galaxy?
answer
They are too far away.
Stars farther away from Earth exhibit smaller parallax shifts. For most stars, the parallax shift is too small to be measured.
question
Our Sun is classified as a G2 star. Vega, which is 26.4 light-years away, is an A0 star, and Barnard's Star is type M5. How do these stars compare in terms of temperature?
answer
Vega is hotter than the Sun, which in turn is hotter than Barnard's Star.
question
Which type of star motion can be measured using the Doppler Effect?
answer
Radial motion
question
Absolute magnitude directly allows us to compute what intrinsic property of a star?
answer
Luminosity
question
If a star is less than 10 parsecs from us, what can we say about how its apprent and absolute magnitudes compare?
answer
Absolute magnitude will be the larger number.
Since larger numbers are dimmer in the magnitude system, this would mean that the star looks brighter than it actually is, indicating it is closer than 10 parsecs.
question
If you want to find a radius value for most stars, what must you first measure about the star?
answer
Luminosity and temperature
There is a definite relationship between luminosity, temperature and radius, so if you know two of these, you can find the third.
question
If a star appears to move back and forth relative to other stars over a six-month period, this motion is due to the star's:
answer
parallax shift.
question
The absolute magnitude of a star is its brightness as seen from a distance of:
answer
ten parsecs.
question
Star A and star B both have an apparent magnitude of 4.0, but star A has an absolute magnitude of 1.0 and star B has an absolute magnitude of 7.0. Which statement below is correct?
answer
Star A and star B appear to have the same brightness, but actually star A is brighter than star B.
question
What physical property of a star does the spectral type measure?
answer
temperature
question
Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral type K2. Which statement below is correct?
answer
Star A is hotter than star B.
question
The Hertzsprung-Russell Diagram plots ________ against the spectral type or temperature.
answer
luminosity or absolute magnitude
question
On the H-R diagram, red supergiants like Betelguese lie:
answer
at the top right.
question
Having nothing to do with trigonometry, ________ parallaxes use the width of absorption lines to estimate the star's luminosity and size and distance.
answer
spectroscopic
question
In a spectroscopic binary system, the star showing the larger blue shift is:
answer
less massive and approaching us at this moment.
question
What is the typical main sequence lifetime of a G-type star?
answer
10 billion years
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