Chapter 6 Quiz: Jessica Horn

Quiz

1. What does the solar system look like? The planets are tiny compared to the distances between them. Our solar system consists of the Sun, the planets and their moons, and vast numbers of asteroids and comets. Each world has its own unique character, but there are many clear patterns among the worlds.
2. What features of our solar system provide clues to how it formed? Four major features proved clues. 1. The Sun, planets, and large moons generally rotate and orbit in a very organized way. 2. The planets divide clearly into two groups: terrestrial and Jovian  3. The solar system contains vast numbers of asteroids and comets, some large enough to qualify as dwarf planets. 4. There are some notable exceptions to these general patterns, 
3.  What theory best explains the features of our solar system? The nebular theory, which 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.
4. Where did the solar system come from? The cloud of gas that gave birth to our solar system was the product of recycling of gas through many generations of stars within our galaxy. This gas consisted of 98% hydrogen and helium and 2% all other elements. 
5. What caused the orderly patterns of motion in our solar system? A collapsing gas cloud tends to heat up, spin faster, and flatten out as it shrinks in size  Our solar system began as a spinning disk of gas and dust, so the orderly motions we observe today came from the orderly motion of this spinning disk.
6. Why are there two major types of planets? Planets formed around solid "seeds" that condensed from gas and then grew through accretion. In the inner solar system, temperatures were so high that only metal and rock could condense, which explains why terrestrial worlds are made of metal and rock. In the outer solar system, cold temperatures allowed more abundant ices to condense along with metal and rock. Icy planetesimals grew large enough for their gravity to draw in hydrogen and helium gas, forming the massive Jovian planets.
7. Where did asteroids and comets come from? Asteroids are the rocky leftover planetesimals of the inner solar system, and comets are the icy leftover polanetesimals of the outer solar system.
8. How do we explain the existence of our Moon and other exceptions to the rules? Most of the exceptions probably arose from collisions or close encounters with leftover planetesimals. Our Moon is most likely the result of a giant impact between a Mars-size planetesimal and the young Earth.
9. When did the planets form? The planets began to accrete in the solar nebula about 4.55 billion years ago.
10.  How do we detect planets around other stars? So far, we are best able to detect extra-solar planets indirectly by observing the planet's effects on the star it orbits. Most discoveries to date have been made with the Doppler technique, in which Doppler shifts reveal the gravitational tug of a planet on a star. We can also search for transits and eclipses in which a system becomes slightly dimmer as a planet passes in frot of or behind its star.