Lesson 11 from quiz

Question 1

The choices below each describe the appearance of a H-R diagram for a different star cluster. Which cluster is the youngest?

Answer 1

The diagram shows main sequence stars of every spectral type O, along with a few giants and supergiants

Question 2

What are the standard units for apparent brightness?

Answer 2

Watts per square metre

Question 3

How does the Sun generate energy today?

Answer 3

Nuclear fusion

Question 4

What two forces are balanced in what we call gravitational equilibrium?

Answer 4

Outward pressure and inward gravity

Question 5

Why are Cepheid variables so important for measuring distances in astronomy?

Answer 5

Their luminosity can be inferred from their period

Question 6

What happens to energy in the convection zone of the Sun?

Answer 6

Energy is transported outward by the rising hot plasma and the sinking of cooler plasma

Question 7

You observe a star in the disk of the Milky Way, and you want to plot the star on a H-R diagram. You will need to determine all of the following except:

Answer 7

Rotation rate of the star

Question 8

How does the Sun’s mass compare to Earth’s mass?

Answer 8

The Sun’s mass is about 300,000 times the mass of Earth

Question 9

From the centre outward, what is the layering of the Sun?

Answer 9

Core, radiation zone, convection zone, photosphere, chromosphere, corona

Question 10

Approximately what basic composition are all stars born with?

Answer 10

Three quarters hydrogen, one quarter helium, with no more than 2% heavier elements

Question 11

If the distance between us and a star is doubled, with everything else remaining the same, the luminosity:

Answer 11

remains the same, but the apparent brightness decreases by a factor of 2

Question 12

Cluster ages can be determined from:

Answer 12

Main sequence turnoff

Question 13

Spectral sequence sorts stars according to

Answer 13

Surface temperature

Question 14

Approximately how long does it take the Sun to orbit the Milky Way galaxy?

Answer 14

230 million years

Question 15

Which of the following statements about spectral types of stars is true?

Answer 15

All of the above

Question 16

Which is the closest temperature of the core of the Sun?

Answer 16

10 million K

Question 17

What is the solar wind?

Answer 17

A stream of charged particles flowing outward from the surface of the Sun

Question 18

Which of the following best answers the question: why does the Sun shine?

Answer 18

As the Sun was forming, gravitational contraction increased the Sun’s temperature until the core became hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine

Question 19

How is the lifetime of a star related to its mass?

Answer 19

More massive stars live much shorter lives than less massive stars

Question 20

Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?

Answer 20

Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity

Question 21

What kinds of objects lie in the disk of our galaxy?

Answer 21

All of the above