Exam 19: Stellar Evolution: on and After the Main Sequence

In the H-R diagram in Figure 19-15 of Universe, 11th ed., the brightest stars in the Pleiades cluster are not on the main sequence but toward the upper right. Why is this? ​ ​

On the Hertzsprung-Russell diagram, in which direction does the position occupied by a star move after hydrogen burning ends in the star's core?

Which way does a star of about 1 M ? evolve, on the Hertzsprung-Russell diagram, at the end of its main-sequence lifetime?

In the approximately 5 billion years since the Sun began its main-sequence phase, its radius has increased by 6% and its surface temperature has increased by 5%. How has its luminosity changed?

After the helium flash in a low-mass star, the star experiences hydrogen burning in a shell around the core. While on the main sequence, this star burned hydrogen in its core and WHAT in the shell around its core?

When the stars of the following open clusters are plotted on an H-R diagram, the luminosity values for the turning points are approximately (in solar luminosities): Coma (7), h + $\chi$ (600), M67 (2), and Pleiades (70). Which cluster is youngest?

If you were to select a star at random within the Milky Way Galaxy, chances are very great that it would be a:

Suppose you pick 100 stars at random from the night sky and plot the apparent magnitude versus color ratio for these stars. What would this plot show you?

When the stars of the following open clusters are plotted on an H-R diagram, the absolute magnitude values for the turning points are approximately: Coma (2.4), h + $\chi$ (-2), M67 (4.5), and Pleiades (0.3). Which cluster is youngest?

An astronomer studying a globular cluster plots its stars on a Hertzsprung-Russell diagram and finds that certain stars in the cluster lie on the horizontal branch. What does this astronomer immediately know about these stars?

In a binary system, the first star to fill its Roche lobe is usually a red giant. What can we say about the nature of the other star when this happens?

If you were able to return to Earth 1 million years into the future, which of the following views of the sky would be most likely?

Mira variables are not as useful as other variable stars in making astronomical calculations because:

What rates of mass loss are typical from red giant stars?

How long will a star whose mass is 0.75 the mass of the Sun stay on the main sequence? (See Table 19-1 of Universe, 11th ed.) ​ ​

A Cepheid variable pulsates because compressing a component in its atmosphere causes this component to ionize and become opaque, thus trapping heat that later causes the star to expand. This atmospheric component is:

During helium burning, some ⁴He combines with ¹⁶O, similar the way in which it combines with ¹²C to form ¹⁶O. What is produced by the ¹⁶O + ⁴He reaction? (The periodic table shown in Box 5-5 of Universe, 11th ed., may be useful.)

In the $\beta$ Lyrae system, the more massive star is the dimmer star. How could this be?

How long is the main-sequence lifetime of a star with 3 times the Sun's mass compared to the lifetime of the Sun? (See Table 19-1 of Universe, 11th ed.) ​ ​

The end product of a red dwarf is believed to be a star of pure helium. How do we know this?