CH12

Use the H-R Diagrams in your textbook to answer the following: What is the approximate luminosity of a main-sequence M star?

0.01 times the sun's luminosity

You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster?

10 billion years

Use the H-R Diagrams in your textbook to answer the following: What is the approximate surface temperature of a B star?

20,000 K

Use the H-R Diagrams in your textbook to answer the following: What is the approximate surface temperature of an F star?

7,000 K

Use the H-R Diagrams in your textbook to answer the following: What is the spectral type of a main sequence star with a luminosity 100 times greater than the sun?

A

Which of the following statements about open clusters is true?

All stars in the cluster are approximately the same age

We can measure the parallax of most stars in our galaxy.

False

Which main-sequence star has the lowest mass?

M

Which of the following stars are brightest at ultraviolet wavelengths?

O and B stars

The stellar spectral sequence, in order of decreasing temperature, is

OBAFGKM.

You see two main-sequence stars with the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude, assuming there is no absorption of either star's light by interstellar gas or dust?

Star 1 is 10 times more distant than Star 2.

How does the rate of hydrogen consumption of a main-sequence B star compare to the hydrogen consumption of our sun?

The "B" star consumes hydrogen at a rate faster than the sun

Which of the following statements about apparent and absolute magnitudes is true?

The absolute magnitude of a star is another measure of its luminosity. A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth. The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared. A star with an apparent magnitude of 1 appears brighter than a star with an apparent magnitude of 2.

If the distance between us and a star is doubled, its apparent brightness will decrease by a factor of four.

True

The more distant a star, the smaller its parallax.

True

Which of the following is the most numerous type of main-sequence star?

an M star

On the main sequence, stars obtain their energy

by converting hydrogen to helium

The age of stars in a cluster can be determined by

determining the main sequence turnoff point.

On a Hertzsprung-Russell diagram, where would you find white dwarfs?

lower left

On a Hertzsprung-Russell diagram, where would you find stars that are cool and dim?

lower right

Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?

mass they are formed with

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

remains the same, but its apparent brightness is decreased by a factor of four

The spectral sequence sorts stars according to

surface temperature

Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?

surface temperature on the horizontal axis and luminosity on the vertical axis

A star's luminosity is the

total amount of energy that the star radiates each second.

On a Hertzsprung-Russell diagram, where would you find red giant stars?

upper right

On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous?

upper right

On a Hertzsprung-Russell diagram, where would you find stars that have the largest radii?

upper right

Which of the following terms is given to a pair of stars that appear to change position in the sky, indicating that they are orbiting one another?

visual binary