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

The Horsehead Nebula in Orion (see Figure 11-3 in Comins,Discovering the Essential Universe,6th ed.)is a distinct dark region surrounded by brighter regions.The Horsehead is an example of a(n):

When plotted on an H-R diagram,the more massive stars of a particular star cluster are on the main sequence and the less massive stars are above the main sequence.Can the age of this cluster be determined? (In other words,how long is it since these stars condensed from the interstellar medium?)

In photographs,the Pleiades open star cluster is surrounded by a bluish haze (see Figure 11-2,Comins,Discovering the Essential Universe,6th ed.).What causes this blue light?

At what stage of its evolutionary life is the Sun?

What particular and very important phenomenon frequently occurs in binary star systems where the stars are very close together?

The source of a protostar's heat is:

Most interstellar matter is too cold to be observed optically.Its radiation is predominantly emitted at longer wavelengths,such as infrared and radio.This behavior is an example of:

What name is given to a young,cool star (spectral class G,K,or M)that is ejecting gas into the interstellar medium?

A Cepheid variable is a:

The energy required to ionize the hydrogen gas in an emission nebula (H II region)comes from:

The distinct blue color of the nebulosity around stars in young clusters such as the Pleiades (see Figure 11-2,Comins Discovering the Essential Universe,6th ed.)is caused by:

Electron degeneracy,which is a result of the Pauli exclusion principle,is important in:

If electrons are collectively compressed into a very small volume (e.g.,within the core of a dying white dwarf star)where quantum mechanical considerations become important in preventing one electron from occupying space near a second electron (Pauli exclusion principle),what is the result?

What condition is considered sufficient for an interstellar cloud to collapse and form a star or stars (i.e.,if this condition holds then the cloud has to collapse)?

What would you expect to find in the population of stars in a globular cluster?

What is the MOST important use of Cepheid variables for astronomers?

How have complex molecules such as formaldehyde (H₂CO)been detected in interstellar clouds?

Main-sequence stars apparently are not larger than a few hundred solar masses.The reason stars of larger mass do NOT exist is that:

What radiation ionizes the hydrogen in an emission nebula (H II region)?

A brown dwarf is a(n):