Chapter 11 Flashcards Preview

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Flashcards in Chapter 11 Deck (17):
1

you know that surface temperature is a stellar property that we infer indirectly. What must we measure directly so that we can infer a star’s surface temperature?

spectral type

2

Which of the following must be true if we are to infer (calculate) a star's luminosity directly from the inverse square law for light?
We have measured the star’s apparent brightness.
We have measured the star’s spectral type.
No interstellar gas or dust absorbs or scatters light between us and the star.
The star must be a member of a binary system.
We have measured the star’s distance.

We have measured the star’s apparent brightness.
No interstellar gas or dust absorbs or scatters light between us and the star.
We have measured the star’s distance.

3

we can measure a star’s mass directly if __________.

it is a member of an eclipsing binary system

4

Before we can use parallax to measure the distance to a nearby star, we first need to know __________.

The Earth-Sun difference

5

Which of the following is a valid way of demonstrating parallax for yourself?

Hold up your hand in front of your face, and alternately close your left and right eyes.

6

What is the cause of stellar parallax?

Earth's orbit around the Sun

7

The more distant a star, the __________.

smaller its parallax angle

8

Approximately what is the parallax angle of a star that is 20 light-years away?

.16 arcseconds

9

If the star Alpha Centauri were moved to a distance 10 times farther than it is now, its parallax angle would

get smaller

10

What do we need to measure in order to determine a star's luminosity?

apparent brightness and distance

11

What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?

the time between eclipses and the average distance between the stars

12

Compared to a main-sequence star with a short lifetime, a main-sequence star with a long lifetime is __________.

less luminous, cooler, smaller, and less massive

13

Compared to a high-luminosity main-sequence star, stars in the upper right of the H-R diagram are __________.

cooler and larger in radius

14

Compared to a low-luminosity main-sequence star, stars in the lower left of the H-R diagram are __________.

hotter and smaller in radius

15

Which of these stars has the coolest surface temperature?

a K star

16

Which of these stars is the most massive?

a main sequence A star

17

Which of these stars has the longest lifetime?

a main sequence M star