Exam 11: The Lives of the Stars From Birth Through Middle Age

Why are higher gas temperatures in the core of a star required to produce nuclear fusion of helium compared with the temperature required for nuclear fusion of hydrogen?

Suppose that,when the stars in a particular open star cluster are plotted in a Hertzsprung-Russell diagram,the turnoff point is at an absolute magnitude of +3.What is the approximate age of this cluster? (See Figure 11-28,Comins,Discovering the Essential Universe,6th ed.)

The Sun is a member of which stellar group?

Why are the stars in an open cluster useful for studying just the early stages of stellar evolution?

Stars in a binary system are useful in studying mass transfers because we know that the two stars have the same:

The lowest mass at which a protostar can have and still become a star (i.e.,start thermonuclear reactions in its core)is:

The next lengthy period in the evolution of a star after hydrogen fusion is helium fusion.What is the main product of this helium fusion?

The components of a binary star,particularly if they are close,can influence each other in various ways.Which statement does NOT describe a likely effect of one star on its companion?

Why does the core of the Sun contain more helium and less hydrogen than the surface of the Sun?

What is the MOST important process that causes a protostar to stop accreting mass?

Long-exposure color photographs of the night sky often show regions that glow red,such as the Rosette Nebula in Figure 11-6 of Comins,Discovering the Essential Universe,6th ed.This distinctive red color is caused by the:

After hydrogen burning ends in a star's core,its position on the Hertzsprung-Russell diagram moves in toward the:

What point defines the end of the pre-main-sequence phase of a star's life and the start of the main-sequence phase?

Evidence of massive amounts of hydrogen gas surrounding some stars comes from:

How do astronomers know that globular clusters are very old?

Compared with the composition of the early Sun,the composition of the gas at the core of a star that has just become a red giant is:

In the Hertzsprung-Russell diagram,how does the position of a typical star change while it is at the main-sequence phase of its evolution?

The Cygnus Loop nebula is characterized by having an arched appearance.The Cygnus Loop is a:

The Pistol in Sagittarius is one of the most massive known stars.But it has lost much of its original 200 solar masses.How long is the entire mass-loss process estimated to take?

In terms of the mass and lifetime of a star,which statement is TRUE?