Question

# If a stars absolute magnitude is numerically equal to its apparent magnitude, what do we know...

If a stars absolute magnitude is numerically equal to its apparent magnitude, what do we know about the star?

A. It is 1 parsec from us.

B. It is 10 parsecs from us.

C. It is 1 light year from us.

D. The star is a main sequence star.

E. [The question is misleading; it is impossible for the two magnitudes to be equal.]

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A star has an apparent magnitude of 6.5 and an absolute magnitude of 4. Ignoring the effects of interstellar dust and gas, we can say for sure that

A. the star is about 30 parsecs away.

B. the star is between 10 and 30 light years away.

C. the star is less than 10 parsecs away.

D. the star is less than 10 light years away.

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The Suns absolute magnitude is about +5. Star X has an absolute magnitude of 5. What is the luminosity of star X compared to that of the Sun, assuming that they have similar temperatures?

A. 1 million times smaller

B. 1 million times larger

C. 10 times greater

D. 10 times less

E. 10,000 times larger

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What do we need to know to determine the size of a star?

A. Its temperature and age

B. Its temperature and absolute magnitude

C. Its temperature and radial velocity

D. Its radial velocity and apparent magnitude

E. [Knowledge of none of the above will allow the determination.]

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Which of the following allow us to calculate the size of a star?

A. Its radial and tangential velocity

B. Its absolute magnitude and apparent magnitude

C. Its luminosity class and temperature

D. Its absolute magnitude and temperature

E. Its mass

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Star X has a surface temperature of 2,900 K and luminosity 100 times that of the Sun. What is its approximate radius, in terms of that of the Sun?

A. The same

B. 10 times larger

C. 100 times larger

D. 40 times larger

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Compared to a star in the middle of the H-R diagram, a star on the upper right part of the diagram is

A. larger.

B. fainter.

C. hotter.

D. [None of the above.]

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