Exam 12: Surveying the Stars

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?

The total amount of power (in watts, for example)that a star radiates into space is called its .

The star Vega has an absolute magnitude of about 4 and an apparent magnitude of about 0. Based on the definitions of absolute and apparent magnitude, we can conclude that .

Which main- sequence star will have the shortest lifetime?

The Earth is about 150 million km from the Sun, and the apparent brightness of the Sun in our sky is about 1,300 watts per square meter. Determine the apparent brightness we would measure for the Sun if we were located five times the earth's distance from the Sun.

On the main sequence, stars obtain their energy

The brightest main- sequence star in a cluster has a temperature of 10,000 K and a luminosity about 100 times greater than the sun. What is the approximate age of the cluster?

Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?

The age of stars in a cluster can be determined by

Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The change in brightness alternates between a small change and a large change. The most likely explanation is that .

What do we mean by the main- sequence turnoff point of a star cluster, and what does it tell us?

Two stars have the same luminosity. Star X is spectral type F, while Star Y is spectral type K. Star X must be larger in radius than Star Y.

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

A star's luminosity is the

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

All main- sequence G stars have approximately the same mass.

Which is brighter in our sky, a star with apparent magnitude 2 or a star with apparent magnitude 7? How many times brighter does it appear?

White dwarfs are all about the same size.

The apparent brightness of a star depends only on its luminosity.

We can measure the radii of stars in eclipsing binary systems.