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Formation of the Solar System - Chap. 8

Review Questions 1-14 and Quick Quiz 25-34
What are the four major features of our solar system that provide clues to how it was formed? Describe each one briefly.
Answer: Four major features provide clues:
(1) The Sun, planets, and large moons generally rotate and orbit in a very organized way.
(2) With the exception of Pluto, the planets divide clearly into two groups: terrestrial and jovian.
(3) The solar system contains huge numbers of asteroids and comets.
(4) There are some notable exceptions to these general patterns.
What is the Nebular Theory, and why is it widely accepted by scientists today?
Answer: Holds that the solar system formed from the gravitational collapse of a great cloud of gas and dust, successfully explains all the major features of our solar system. The nebular theory of solar system formation gained wide acceptance because of its success in explaining the major characteristics of our solar system.
What do we mean by the solar nebula? What was it made of and where did it come from?
Answer: Solar nebula is a massive cloud of gas and dust that collapses into itself, compresses the gas, heats up, and eventually (assuming its massive enough) begins nuclear fusion creating a star. The dust clumps together to form planetary bodies and whatnot. And you get a solar system.
Describe each of the three key processes that led the solar nebula to take the form of a spinning disk. What observational evidence supports this scenario?
Answer: A collapsing gas cloud naturally tends to
heat up, spin faster, and flatten out as it shrinks in size. Thus, our solar system began as a spinning disk of gas and dust. The orderly motions we observe today all came from the orderly motion of this spinning disk.
List the four categories of materials in the solar nebula by their condensation properties and abundance. Which ingredients are present in terrestrial planets? In jovian planets? In comets and asteroids? Explain why?
Answer: 1. Hydrogen and Helium gas (98%)
2. Hydrogen compounds (1.4%)
3. Rock (0.4%)
4. Metal (0.2%)
Rock and Metal are in terrestrial planets
Jovian - Hydrogen and Helium and hydro compounds
comets and asteroids - ice and rock
What was the frost line in the solar nebula? Explain how temperature differences led to the formation of two distinct types of planets.
Answer: the distance at which Hydrogen compounds are cold enough for ices to condense - which lay between the present-day orbits of Mars and Jupiter.
Briefly describe the process by which terrestrial planets are thought to have formed.
Answer: Terrestrial planets formed inside the frost line, where accretion allowed tiny, solid grains of metal and rock to grow into planetesimals that ultimately merged to make the planets we see today
How was the formation of jovian planets similar to that of the terrestrial planets? How was it different? Why did the jovian planets end up with so many moons?
Answer:Similar-The formation was similar due to accretion which is the process of small solid rock"seed" as they grew into planets and once the gases came from a solid material. The two also have planetesimals which are "pieces of planets".
Different- As each jovian planet is wrapped around it own disk of gas but terrestrials don't have this.
Moons- Because they were captured in the planetary orbit when they lost energy to drag in the extended disks of gas that surrounded these planets as they formed. they would have been slowed by the friction with gas. It slowed planetesimals orbital energy enough to make it an orbiting moon.
What is the solar wind, and what roles did it play in the early solar system?
Answer: A stream of charged particles (such as protons and electrons) continually blown outward in all directions from the Sun. Back many years ago a young Sun probably had strong solar wind. It also blew interstellar clouds and left the Sun with a greatly diminished angular momentum and with a smaller rotation that we see today.
In the context of planet formation, what are asteroids and comets? Briefly explain why we find asteroids in the asteroid belt and comets in the Kuiper belt and Oort cloud.
Answer: Asteroids are the rocky leftover planetesimals of the inner solar system. Comets were the ice-rich leftover planetesimals in the outer solar system. Comets have remained near their orginal orbits in the same general plane which happens to be the donut shaped region called the Kuiper Belt. Comets are found in the Oort Cloud because they are essential "kicked-out" in random directions and roam around the jovian planets and suffered close gravitaional encounters with these planets.
What was the heavy bombardment and when did it occur?
Answer: left over planetesimals that collided with planets, moons or each other, evidence of heavy cratering on objects such as moons, Juniper . Also know as intense cratering and created impact craters. Possibly occurred 4.0 to 3.8 billion years ago.
How do we think the Moon formed, and what evidence supports this hypothesis?
Answer: We look at the impact at a speed and angle that would have blasted rock from Earth's outer layers in space. According to computer simulations, this material could have collected into orbit around out planet, and accretion within this rind of debris could have formed the Moon. Evidence to support this hypothesis comes from two features of the Moon's composition like the moon's overall composition is similar to Earth's and the Moon has a much smaller proportion of easily vaporized ingredients such as water than Earth.
Describe the technique of radiometric dating. What is half -life?
Answer: This is the method we use to measure the age of a rock. It relies on careful measurements fo the proportions of various isotopes in the rock.

The time it would take for half fo the parent nuclei in the collection to decay or the time if takes for half of the nuclei in a given quanity of a radioactive sustance to decay.
How old is the solar system, and how do we know?
Answer- 4.55 Billion years ago we know this because there has been careful analysis of radioactive isotopes in meteorite shows and many meteorites appear to have been unchanged since they have condensed and accreted in the early solar system. (Radiometric dating)
QQ 25. How many of the planets orbit the Sun in the same direction that Earth does? (a) few (b) most (c) all
Answer: B. Most ??
QQ 26. What fraction of the moons of the planets orbit in the same direction that their planets rotate? (a) some (b) most (c) all
Answer: (b) Most (Triton is the exception)
QQ 27. The solar nebula was 98% (a) rock and metal (b) hydrogen compounds (c) hydrogen and helium.
Answer: C
QQ 28. Which of the following did not occur during the collapse of the solar nebula? (a) spinning faster (b) heating up (c) concentrating denser materials nearer the Sun
Answer: C
QQ 29. What is Jupiter's main ingredient? (a) rock and metal (b) hydrogen compounds (c) hydrogen and helium
Answer: C
QQ 30. Which lists the major steps of solar system formation in the correct order? (a) collapse, accretion, condensation (b) collapse, condensation, accretion (c) accretion, condensation and collapse
Answer: B
QQ 31. Leftover ice-rich planetesimals are called (a) comets (b) asteroids (c) meteorites
Answer: A
QQ 32. Why didn't a terrestrial planet form at the location of the asteroid belt? (a) there was never enough material in that part of the solar nebula (b) The solar wind cleared away nebular material there (c) Jupiter's gravity kept planetismals from accreting
Answer: (c)
QQ 33. What's the leading theory for the origin of the Moon? (a) It formed along with the Earth (b) It formed from the material ejected from Earth in a giant impact (c) It split out of a rapidly rotating Earth
Answer: B
QQ 34. About how old is the solar system? (a) 4.5 million years (b) 4.5 billion years (c) 4.5 trillion years
Answer: B