Question 1

Suppose two stars with the same luminosity are at different distances from Earth. Which has the greater apparent brightness?

Accepted Answer

the closer star  The closer the object, the brighter it will appear.

Question 2

What important property of a star do we learn from its spectral class?

Accepted Answer

temperature  The temperature of a star determines at what wavelengths its atmosphere absorbs photons.

Question 3

Which of the following methods is useful for determining a star\'s approximate surface temperature?

Accepted 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 4

Why are we unable to measure parallax shifts for most of the stars in the Galaxy?

Accepted 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 5

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?

Accepted Answer

Vega is hotter than the Sun, which in turn is hotter than Barnard\'s Star.

Question 6

Which type of star motion can be measured using the Doppler Effect?

Accepted Answer

Radial motion

Question 7

Absolute magnitude directly allows us to compute what intrinsic property of a star?

Accepted Answer

Luminosity

Question 8

If a star is less than 10 parsecs from us, what can we say about how its apprent and absolute magnitudes compare?

Accepted 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 9

If you want to find a radius value for most stars, what must you first measure about the star?

Accepted 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 10

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:

Accepted Answer

parallax shift.

Question 11

The absolute magnitude of a star is its brightness as seen from a distance of:

Accepted Answer

ten parsecs.

Question 12

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?

Accepted Answer

Star A and star B appear to have the same brightness, but actually star A is brighter than star B.

Question 13

What physical property of a star does the spectral type measure?

Accepted Answer

temperature

Question 14

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?

Accepted Answer

Star A is hotter than star B.

Question 15

The Hertzsprung-Russell Diagram plots ________ against the spectral type or temperature.

Accepted Answer

luminosity or absolute magnitude

Question 16

On the H-R diagram, red supergiants like Betelguese lie:

Accepted Answer

at the top right.

Question 17

Having nothing to do with trigonometry, ________ parallaxes use the width of absorption lines to estimate the star\'s luminosity and size and distance.

Accepted Answer

spectroscopic

Question 18

In a spectroscopic binary system, the star showing the larger blue shift is:

Accepted Answer

less massive and approaching us at this moment.

Question 19

What is the typical main sequence lifetime of a G-type star?

Accepted Answer

10 billion years

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