Lesson 11 from quiz Flashcards
The choices below each describe the appearance of a H-R diagram for a different star cluster. Which cluster is the youngest?
The diagram shows main sequence stars of every spectral type O, along with a few giants and supergiants
What are the standard units for apparent brightness?
Watts per square metre
How does the Sun generate energy today?
Nuclear fusion
What two forces are balanced in what we call gravitational equilibrium?
Outward pressure and inward gravity
Why are Cepheid variables so important for measuring distances in astronomy?
Their luminosity can be inferred from their period
What happens to energy in the convection zone of the Sun?
Energy is transported outward by the rising hot plasma and the sinking of cooler plasma
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:
Rotation rate of the star
How does the Sun’s mass compare to Earth’s mass?
The Sun’s mass is about 300,000 times the mass of Earth
From the centre outward, what is the layering of the Sun?
Core, radiation zone, convection zone, photosphere, chromosphere, corona
Approximately what basic composition are all stars born with?
Three quarters hydrogen, one quarter helium, with no more than 2% heavier elements
If the distance between us and a star is doubled, with everything else remaining the same, the luminosity:
remains the same, but the apparent brightness decreases by a factor of 2
Cluster ages can be determined from:
Main sequence turnoff
Spectral sequence sorts stars according to
Surface temperature
Approximately how long does it take the Sun to orbit the Milky Way galaxy?
230 million years
Which of the following statements about spectral types of stars is true?
All of the above
Which is the closest temperature of the core of the Sun?
10 million K
What is the solar wind?
A stream of charged particles flowing outward from the surface of the Sun
Which of the following best answers the question: why does the Sun shine?
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
How is the lifetime of a star related to its mass?
More massive stars live much shorter lives than less massive stars
Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?
Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity
What kinds of objects lie in the disk of our galaxy?
All of the above
