Origin of Planets





the nebular model accounts for the formation of the planets with the following sequence

A gravitational collapse, accretion, condensation, differentiation.

B condensation, gravitational collapse, accretion, differentiation.

C gravitational collapse, condensation, accretion, differentiation.

D accretion, differentiation, gravitational collapse, condensation.



if the terrestrial planets formed by homogeneous accretion, then

A they formed an iron core first, and a silicate crust later.

B the solar nebula changed during their formation.

C Earth's first atmosphere was rich in hydrogen.

D all of these.



in order for the terrestrial planets to form, the planetesimals had to

A accrete to make the proto planets.

B move in from the asteroid belt.

C collide and fragment each other into smaller pieces.

D melt from radioactive decay and then reform.



in the chemical condensation sequence, the terrestrial planets end up with very little hydrogen and helium (compared to the Jovian planets) because the

A original nebula contain little hydrogen and helium.

B sun drew in hydrogen and helium from the inner nebula.

C temperatures were too high for these to condense.

D temperatures were too low for these to condense.



when a hot cloud cools, which of the following will be true?

A volatile elements condense first

B refractory elements condense first

C neither a nor be; all materials will condense at the same time

D neither a nor b; hot clouds do not cool sufficiently for condensation to occur



the most probable process for the formation or acquisition of the planets of the sun is

A the freezing of immense gas clouds by the cold temperature of space

B the break-up of one single large companion body to the sun, by tidal distortion

C capture from outer space by gravity

D relatively slow collection of smaller objects by mutual gravitational attraction and sticking, or accretion



the formation of planets depends upon

A a balance between gravity and rotational force

B a balance between gravity and turbulence

C a balance between turbulence and rotational force

D attraction of extra matter from the surrounding cloud after the sun has formed



the solar system originated

A about 500 million years ago

B about 5 billion years ago

C about 50 billion years ago

D about 500 billion years ago



the large planetesimals would have grown the fastest because

A they had a layer of material to trap fragments.

B their stronger gravity would pull in additional material.

C both of these.

D none of these.



compared to the formation of the terrestrial planets, Jupiter may have

A formed at a much higher temperature.

B condensed gravitationally rather than by accretion.

C condensed with mostly metallic materials.

D required a much longer time to form.

E not followed the condensation sequence at all.



the most likely formation mechanism for the solar system is that

A the sun and planets slowly condensed to their present form from a gas and dust cloud

B the solar system was once a galaxy, from which the sun and planets are remnants, after evolution

C the sun captured the planets as they drifted through space

D planets were spun out of the sun as smaller gas clouds and subsequently condensed



refractory elements are

A elements that split easily during nuclear fusion

B elements that condense easily

C elements that burn

D elements that bend light



the material which would begin to condense at the highest temperature is

A helium

B iron and nickel

C water vapor

D rock-like materials and silicates



the modern nebular-condensation model for the formation of the solar system is supported by the observation of

A Mercury having a larger, denser core than Earth.

B Mars having a smaller, denser core than Earth.

C the Jovian planets being less dense than the terrestrial planets.

D all of the above.

E (a) and (b) above.



what important event occurred while the sun was in its t tauri phase (a ph young stars go through in which they have strong stellar wind similar to the solar wind)?

A Jupiter was formed

B the Earth-moon system was formed

C the sun completed its contraction so that it became like it is today

D gas and dust remaining in the solar system were dispersed



in the early solar nebular disk, before planets were formed,

A temperatures decreased with increasing distance from the center of the disk.

B temperatures were essentially constant throughout the nebula.

C temperatures increased with increasing distance from the center of the disk.

D temperatures varied with the sizes of the planets.



the modern nebular theory for the formation of the solar system explains which chemical feature of the solar system?

A the inner planets are made of terrestrial materials.

B the outer planets are made of solar and icy materials.

C the comets are made of terrestrial materials.

D (a) and (b) only.

E (b) and (c) only.



proto planets of the Jovian planets could have grown very hot from

A heat from the sun.

B friction with the gas.

C tidal forces due to the sun.

D the in fall of material at high velocity.



which of the following have been proposed as basic models for satellite formation?

A fission of a rapidly spinning planet.

B co-accretion of the planets and satellites.

C gravitational capture of planetesimals.

D a, b, and c have been proposed as models for satellite formation.



the solar gale

A blew the atmospheres away from all the planets

B blew the atmospheres away from the inner planets

C sucked the atmospheres of the inner planets into the proto sun

D forced the proto planets into their present orbits



the t-tauri wind

A is the result of "t" reactions in the star tauri

B results from the triggering of nuclear reactions in a star's core

C was caused by the vortex which formed Jupiter

D blows in the south pacific in the vicinity of the tauri island



planetesimals

A were formed from the collision of grains in the solar nebula

B were formed from proto planets

C resulted from the collision of proto planets

D none of the above



the birthplace of the sun and planets (and of other stars and maybe their planets) is thought to have been

A at the centers of supernova explosions

B in black holes dotted about the universe

C in cool gas and dust clouds

D in the centers of galaxies



accretion among the grains in the solar nebula would have been aided by

A high-velocity collisions.

B gravity.

C static electricity.

D all of these.



the modern nebular theory for the formation of the solar system explains very well

A the retrograde rotation of Venus

B the directions of the orbital motions of the planets

C the coplanar orbits (along the ecliptic) of the planets

D (a) and (b).

E (b) and (c).



an observation which supports the theory of planet formation within a collapsing cloud is

A direct observation of other planetary systems

B the existence of binary stars

C the existence of black holes

D the existence of galaxies



condensation is the process by which a particle grows

A by sticking together other particles

B by adding one atom at a time

C both of these

D none of these



the compounds which would begin to condense at the highest temperature in the solar nebula are those of

A hydrogen.

B helium.

C iron and nickel.

D water vapor.

E rock-like materials and silicates.



condensation is the process by which a particle grows

A by sticking together other particles.

B by adding one atom at a time.

C both of these.

D none of these.



the most probable time sequence for the formation of the solar system was that

A the sun formed initially, and the planets and major moons were captured mu later as they drifted by the sun

B the sun formed first, the planets were spun off from the sun, and the moon in turn were spun off from the planets

C the sun contracted first as a gas ball, and the planets and moons formed shortly afterwards by accretion and condensation

D the planets formed first out of the cold gas and dust nebula, followed by the sun, which formed when the gas had become much hotter



according to the nebular models the planets have a common orbital plane because they

A were aligned by the sun's gravity.

B were aligned by the interaction of the planets on themselves.

C formed from a rotating, pancake shaped cloud of gas.

D formed from coplanar rings of gaseous material.



according to the accepted theory of the formation of the solar system

A the planets formed earlier than the sun

B the planets and sun formed at about the same time

C the planets formed after the sun had expelled much of the solar nebula

D the planets formed from cometary debris



which of the following is the major cause for the difference in the chemical compositions of the planets?

A the different temperatures at which compounds condense

B the t-tauri wind

C the difference in the distribution of elements in the nebular disk

D the metals condensed near the sun, leaving little for the outer planets



early phases of planetary formation were characterized by

A the breaking apart of very large objects into planets

B collapse of material under gravity

C condensation of hot gas clouds

D slow growth of small objects as grains of dust stick together



condensation in the solar cloud probably led to the formation of

A icy grains beyond the present orbit of Mars.

B metallic grains near the present orbit of Mercury.

C silicate grains near the present orbit of Earth.

D all of these.



the formation of terrestrial-type planets around a star is most likely to have occurred by what process?

A break-up of a large disk of matter which formed around the star

B condensation of gas from the original star cloud

C accretion, or slow accumulation of smaller particles through collisions attraction

C capture by the star of objects traversing the depths of space



according to the model for planet formation, chemical differences between the gas giant planets and terrestrial planets are a result of

A elements with differing melting points condensing at different distances from the center of the cloud.

B elements existing in differing proportions at different distances from the center of the cloud.

C larger bodies being able to attract heavier elements than the smaller objects.

D the sun pushing the lighter elements out to where they could form the Jovian planets.



if a planet were abundant in refractory elements but had few volatile elements, what might be concluded about it?

A the planet was formed in a region of low temperature

B the planet was formed in a region of high temperature

C the planet was subjected to large temperature variations in a short time interval

D no conclusions may be drawn



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