Condensation of Interstellar Clouds





the original condensation from which an object forms is created by

A an explosion

B random motion within a cloud

C overall contraction of a cloud

D expansion of the universe



which of the following effects is most important in the initial formation of most celestial objects

A rotation

B pressure of the gases

C an explosion

D random motion



the contraction of an interstellar cloud to become a star is caused by

A magnetic forces.

B electric forces.

C nuclear forces.

D gravitational forces.

E both (a) and (b) above, for they are closely related.



the formation of a clump depends upon turbulence being overcome by

A gravity

B magnetic forces

C external forces

D internal pressure



interstellar gas clouds may collapse to form stars if they

A have very high temperatures.

B encounter a shock wave.

C are rich in helium.

D all of these.



the basic property of the molecular cloud that causes its collapse into a star is:

A its own gravitational forces.

B the pressure from surrounding clouds.

C nuclear forces that are as yet not understood.

D gas pressure forces that tend to make such clouds condense.



it is now believed that all objects in the universe formed

A from the collapse of large clouds of gas

B at the same time

C during a universal explosion

D from quasars



star formation takes place in

A interstellar clouds

B intergalactic space

C supernovae remnants

D unknown conditions since it is no longer occurring



the first step in the formation of a star from a cloud of gas is

A local heating in the cloud

B the formation of a local condensation in the cloud

C formation of a local, rapidly rotating vortex in the cloud

D condensation of a few bits of rock in the cloud



during the star formation process the formation of planets depends on

A a strong magnetic field

B a high temperature

C the proper rate of growth of bits of rock as they collect atoms of gas from the cloud

D a close encounter with another star retarding the contraction



which of the following is not considered a possible trigger to begin the collapse of an interstellar gas cloud?

A a shock wave from a supernova.

B a shock wave occurring during the formation of very massive stars.

C a shock wave resulting from radiation from nearby emission nebulae.

D a shock wave passing around the galaxy.

E all of the above are considered likely triggers.



local condensations in clouds are formed of

A gas only

B dust only

C gas and dust

D unknown particles



which of the following does not occur during the formation of stars

A a cloud collapses under its own force of gravity

B a turbulent condensation forms in a large cloud of gas

C a collapsing cloud of gas breaks apart to form a cluster of stars

D planets form within a collapsing cloud of gas



which of the following can trigger star formation

A a heat source

B turbulence

C a supernova explosion

D the passage of a star through a cloud of gas



the formation of a star within a large cloud of gas requires

A gravity to overcome the rotation of the cloud

B gravity to overcome the turbulent motion of the cloud

C a rapidly rotating cloud

D a cloud without any rotation or turbulence



evidence for the general existence of an interstellar medium is

A reddening of the light of distant stars

B radio emission from atoms and molecules in space

C spectral lines in the spectra of stars which don't fit the normal pattern

D all of the above



in which regions of the universe are stars thought to be born?

A in the relatively empty space between the galaxies

B in the centers of globular clusters

C in large clouds of dust and gas

D in the centers of planetary nebulae



the great amount of compression that must take place to form a star is caused by

A gravity

B the pressure of the surrounding gas pushing in

C nuclear reactions

D collisions with other stars



clouds of gas and dust between stars can be observed by

A reddening of star light

B patches of few stars in regions of many stars

C "unusual" spectral lines in the spectrum

D all of the above



the temperature in an interstellar cloud before star formation is

A a few thousand degrees

B about room temperature

C somewhat below freezing

D only a few degrees above absolute zero



as an object collapses, the force of gravity

A becomes weaker

B eventually disappears

C stays the same

D gets stronger



new stars are formed from

A huge, cool dust and gas clouds

B free space - out of pure energy

C activity in the centers of galaxies

D supernova remnants



the density of gas in a typical interstellar cloud is

A a billion trillion atoms per cubic inch

B a billion atoms per cubic inch

C a thousand atoms per cubic inch

D less than one atom per cubic inch



a fragment of a gas cloud can contract to start star formation

A only if it is less than 80 times as massive as the sun

B unless it is perturbed, as by a supernova explosion which would disrupt it

C if it passes through a spiral arm

D only when its core temperature reaches several million degrees



the formation of a star generally involves

A collapse caused by radiation pressure

B expansion caused by gravity

C collapse under the influence of gravity

D expansion caused by nuclear reactions



star formation begins when

A an entire large cloud begins to collapse

B a small condensation within a cloud begins to collapse

C a light source is created within a cloud

D gravity is turned on in a cloud



the most likely places where stars and planetary systems are forming in the universe are

A in the centers of black holes

B in regions surrounding quasars

C in cool gas and dust clouds

D in the rarified outer space between galaxies



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