CH 19 HW

What happens to a newly forming star with an excess of heat?

It will likely have a rapid contraction rate.

What is primarily responsible for the gravitational contraction of an interstellar cloud?

Its mass.

As a clump of interstellar gas contracts to become a main-sequence star, what does its changing position on the H-R diagram indicate?

How its outward appearance is changing.

When does a newly forming star have the greatest luminosity?

When its internal temperature becomes high enough for nuclear fusion.

What is the energy source of a newly forming star at its greatest luminosity?

Nuclear fusion of hydrogen into helium.

What is the size of the 'dust' component of the interstellar medium?

Grains of sand.

What process causes the red/pink color in star-forming regions?

Emission.

What kind of light is best for looking inside a cold dark cloud to see warm stars forming inside?

Infrared.

What was the interstellar cloud from which our Sun formed?

Thousands of times more massive than the Sun.

How does a protostar that will eventually turn into a star like the Sun compare in luminosity?

It is significantly less luminous.

How do the properties of long-lived stars compare to those of short-lived stars?

Long-lived stars begin their lives with less mass and a smaller amount of hydrogen fuel.

How long would a main-sequence star twice as massive as the Sun last?

Much less than half as long as the Sun.

What is the current theory of star formation based upon?

Amassing evidence from many different regions of the Galaxy.

What would happen if the initial interstellar cloud were much more massive?

The formation of more stars.

How long does a typical open cluster take to dissolve?

About the same amount of time since the dinosaurs walked on Earth.

What is one primary difference between the Pleiades cluster and Omega Centauri?

The Pleiades cluster is much younger.

If the HR diagram were redrawn for a much younger cluster, where would the main-sequence turnoff shift?

Higher temperature.

Is it possible for some stars in a cluster with a wide range of stellar masses to die out before others have finished forming?

Yes, low-mass stars evolve at a slower rate than high-mass ones; O or B stars may die out first.