Astronomy Chapter 8 – Flashcards
Unlock all answers in this set
Unlock answersquestion
The age of our solar system is approximately
answer
4.6 billion years.
question
Why did the solar nebula flatten into a disk?
The force of gravity from the planets pulled the material downward into a flat disk.
answer
It flattened as a natural consequence of collisions between particles in the spinning nebula, changing random motions into more orderly ones.
question
The age of the solar system can be established by radioactive dating of
answer
oldest meteorites
question
What kind of material in the solar nebula could remain solid at temperatures as high as 1,500 K, such as existed in the inner regions of the nebula?
answer
Metal
question
Where did the elements heavier than hydrogen and helium come from?
answer
They were produced inside stars.
question
Planet Formation
answer
Terrestrial- Accreted from planetesimals of rock and metal, surface dramatically altered during the heavy bombardment
Jovian- large moons formed in surrounding disk of material, formed in regions cold enough to freeze water, ejected planetesimals that are new Oort cloud comets, formed in region of solar system with lower orbital speeds.
question
What percentage of the solar nebula's mass consisted of rocky material?
answer
0.4 percent
question
What happened during the accretion phase of the early solar system?
answer
Particles grew by colliding and sticking together.
question
What do meteorites reveal about the solar system?
answer
They reveal that the age of the solar system is approximately 4.6 billion years.
question
According to our theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?
answer
The laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk.
question
Which of the following lists the ingredients of the solar nebula from highest to lowest percentage of mass of the nebula?
answer
light gases (H, He), hydrogen compounds (H2O, CH4, NH3), rocks, metals
question
Observations of young stars (as well as theory) tell us that when the Sun was young the solar wind
was stronger than it is today.
was weaker
answer
was stronger than it is today.
question
What percentage of the mass of the solar nebula consisted of elements other than hydrogen and helium?
answer
2 percent
question
According to our theory of solar system formation, why do we find some exceptions to the general rules and patterns of the planets?
answer
Most of the exceptions are the result of giant impacts.
question
Abundance highest to lowest
answer
hydrogen & helium, hydrogen compounds, rock, metals
Temp: metals, rocks, hydrogen compounds, and hydrogen & helium
Solar Nebula farthest to closes: Hydrogen compounds, rock, metals
question
According to the nebular theory, what are asteroids and comets?
answer
They are leftover planetesimals that never accreted into planets.
question
What percentage of the solar nebula's mass consisted of hydrogen and helium gases?
answer
98 percent
question
Which of the following is the origin of almost all the large moons around the Jovian planets?
answer
They were formed by condensation and accretion in a disk of gas around the planet.
question
Why are the inner planets made of denser materials than the outer planets?
answer
In the inner part of the nebula only metals and rocks were able to condense because of the high temperatures, whereas hydrogen compounds, although more abundant, were only able to condense in the cooler outer regions.
question
What is the most likely reason that there are no giant planets beyond Neptune?
answer
By the time planetesimals grew to a large enough mass to hold onto an atmosphere, the solar nebula had been blown away.
question
At first, the Sun's present-day rotation seems to contradict the prediction of the nebular theory because
answer
the theory predicts that the Sun should have been rotating fast when it formed, but the actual rotation is fairly slow.
question
According to the nebular theory, how did the Kuiper belt form?
answer
It is made of planetesimals between the orbits of Mars and Jupiter that never formed into a planet.
It is made of planetesimals that formed beyond Neptune's orbit and never accreted to form a planet.
question
Why did the solar nebula heat up as it collapsed?
Collisions among planetesimals generated friction and heat.
answer
As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy.
question
What was the frost line of the solar system ?
answer
the distance from the Sun where temperatures were low enough for hydrogen compounds to condense into ices, between the present-day orbits of Mars and Jupiter
question
Which of the following are relatively unchanged fragments from the early period of planet building in the solar system?
asteroids
Kuiper belt comets
the moons of Mars
Oort cloud comets
answer
All of the above
question
Formation of the solar system
answer
large cloud of gas & dust, contraction of the solar nebula, condensation of particles, accretion of planetesimals, clearing of the solar nebula
