Sunday, March 3, 2013

Study Guide Ch9

Chapter 9 - Formation & Structure of Stars

Study Guide
Answer is slashed threw its not the right one if in red it might be the answer.


Question 1
As a star begins to form, the initial energy source is from
gravitational potential energy.

Question 2
There is a main sequence mass-luminosity relation because
helium fusion produces carbon.
stars expand when they become giants.
more massive stars support their larger weight by making more energy.
the helium flash occurs in degenerate matter.
all stars on the main sequence have about the same radius.

Question 3
 What causes the outward gas pressure that balances the inward pull of gravity in a main sequence star?
the rapid outward flow of gas
the rapid inward flow of the gas
the high temperature of the gas
the high density of the gas
c and d

Question 4
Which of the following is NOT evidence of the existence of an interstellar medium?
molecular absorption lines in the spectra of cool stars

Question 5
 Opacity is
a measure of the resistance to the flow of radiation (photons) through a gas.

Question 6
____ is the thermonuclear fusion of hydrogen to form helium operating in the cores of massive stars on the main sequence.
The CNO cycle

Question 7
The carbon-nitrogen-oxygen cycle
combines four hydrogen nuclei to form one helium nucleus, which produces energy.

Question 8
The ____ is the nuclear fusion of three helium nuclei to form a carbon nucleus.
proton-proton chain
Carbon-Nitrogen-Oxygen cycle (CNO cycle)
triple-alpha process
Coulomb barrier
infrared cirrus

Question 9
Molecular clouds can be observed
using infrared telescopes to detect ionized gas in the clouds.

Question 10
While on the main sequence a star's primary energy source comes from
nuclear fusion.

Question 11
In the proton-proton chain
energy is produced in the form of gamma rays and the velocity of the created nuclei.

Question 12
Emission nebulae are also called ____ because they are composed of ionized hydrogen.
HII regions

Question 13
____ are star-like objects that contain less than 0.08 solar masses and will never raise their core temperatures high enough that the proton-proton chain can begin. Other minor fusion reactions do occur in these objects.  They fall in a gap between the low-mass M dwarf stars and the massive planets in which nuclear fusion never occurs.
Brown dwarfs

Question 14
Convection is important in stars because it
b and c
{mixes the gases of the star/transports energy outward in the star}

Question 15
The free-fall contraction of a molecular cloud
can be initiated by shock waves from supernovae.

Question 16
Absorption lines due to interstellar gas
are more narrow than the lines from stars because the gas has a lower pressure than stars.

Question 17
Absorption lines due to the interstellar medium indicate that some components of the interstellar medium are cold and of a very low density because
the lines are extremely narrow.

Question 18
The creation of ____ require(s) that a young hot star (T 25,000 K) be relatively nearby.
emission nebulae

Question 19
The lower edge of the Main Sequence band is known as ____ and represents the location in the H-R diagram at which stars begin their lives as main sequence stars.
the zero-age main sequence

Question 20
What characteristic of a star primarily determines its location on the main sequence?
mass

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