Astrology Chapter 6

The protoplanetary disk contains

-hydrogen and helium gas throughout -a small amount of solid flakes made out of rocks everywhere beyond the rock/metal line and metals -icy flakes of hydrogen compounds only beyond the frost line

Hydrogen compounds such as water, methane and ammonia can freeze to form ice particles in the disk if the temperature is less than 150K. Roughly what is the minimum distance from the protostar at which these ices can form? 3AU 1AU 3.5AU 7.5AU

3.5 AU

According to modern scientific dating techniques, approximately how old is the solar system?

4.5 billion years

The orbital distance of Earth is 1 AU and the orbital radius of Jupiter is 5 AU. Roughly how much warmer was the region where Earth formed than where Jupiter formed?

About 4 times as hot

Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?

All the planets orbit counterclockwise around the Sun.

Suppose the solar nebula had been too warm for ices to condense anywhere. If a planet had still formed at Jupiter's location, it most likely would have

Been similar in composition to Earth, with a much smaller mass than the real Jupiter.

The jovian planets contain large abundances of hydrogen and helium because

Beyond the frost line the gravity of large, ice-rich planetesimals captured the abundant H and He gas.

As the solar nebula collapsed, it became a disk because

Collisions between particles made the particles go in more or less the same direction.

What is the main reason that Earth's composition is different from Jupiter's?

Compared to Jupiter, Earth formed in a hotter region where only rocks and metal could exist as solids.

Why does the cloud heat up as it collapses?

Gravitational potential energy is converted into heat and other forms of energy

According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?

It got hotter, its rate of rotation increased, and it flattened into a disk.

As the solar nebula collapsed under its own gravity what happened?

It heated and spun up.

What do we mean by the frost line when we discuss the formation of planets in the solar nebula?

It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ice to condense.

The jovian planets in our solar system are _________.

Jupiter, Saturn, Uranus, and Neptune

What is the composition of most planets?

Mostly rock and metal vs a lot of hydrogen and helium

If a star forming cloud had absolutely no initial net rotation, would it flatten into a disk as it collapsed?

No

Which of the following objects fits neither the terrestrial nor jovian category? Venus Earth Neptune Pluto

Pluto

What explains the composition of pluto?

Pluto formed beyond the frost line but never became massive enough to capture gases.

How does composition relate to size for most of the planets?

Rock and metal planets are small and planets with abundant hydrogen and helium are large

Because of the temperature in the protoplanetary disk,

Rocks and metals froze in both the inner and outer regions and ices froze only in the outer region.

In the intermediate region, which substances can exist as frozen flakes?

Rocks and metals only

Beyond the frost line, which materials can exist as frozen flakes?

Rocks, metals, and hydrogen compounds

Accreted from planetesimals of rock and metal jovian or terrestrial?

Terrestrial

What is the giant impact hypothesis for the origin of the Moon?

The Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object

Why do all planets orbit the sun in the same direction?

The direction of rotation is determined by the original rotation of the cloud.

Which region contains the largest planetesimals?

The outermost region (beyond the frost line)

Which solar system bodies contain significant amount of hydrogen and helium gases?

The sun and jovian planets

Why didn't the terrestrial planets acquire H and He gas?

The terrestrial planets had too little mass to capture these gases

Why do the jovian planets have compositions quite similar to that of the sun?

Their composition reflects that of the original solar nebula.

If the solar nebula initally had no angular momentum

There would not be any planets orbiting the sun.

The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did the elements heavier than hydrogen and helium come from?

They were produced by stars that lived and died before our solar system was born.

The planet in our solar system with the highest average surface temperature is _________.

Venus

Suppose the solar nebula had cooled much before the solar wind cleared away the remaining gas. In that case, the terrestrial planets likely would have ended up

With a higher abundance of hydrogen compounds and larger size.

Suppose you start with 1 kilogram of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?

You'll have 0.25 kilogram of the radioactive substance remaining.

Jovian Planets:

are large and far from the sun, mostly hydrogen, helium, hydrogen compounds and they lack any solid surface

Terrestrial Planets:

are small and close to the sun, mostly metal and rock

When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals EXCEPT _________.

carbon dioxide

Which of the following types of material can condense into what we call ice at low temperatures?

hydrogen compounds

Accreted from icy planetesimals jovian or terrestrial?

jovian

Ejected ice planetesimal that are now Oort cloud comets jovian or terrestrial?

jovian

Formed in a region of the solar system with lower orbital speeds jovian or terrestrial?

jovian

Formed in regions cold enough for water to freeze jovian or terrestrial?

jovian

Large moons formed in surrounding disks of material jovian or terrestrial?

jovian

According to our theory of solar system formation, what are asteroids and comets?

leftover planetesimals that never accreted into planets

Inside the frost line, what are the planetesimals made out of?

metals and rock only

In essence, the nebular theory holds that _________.

our solar system formed from the collapse of an interstellar cloud of gas and dust

Surfaces dramatically altered during the heavy bombardment jovian or terrestrial?

terrestrial

How does composition relate to position in the solar system

the inner planets are mostly rocks and metal and the outer planets have a lot of hydrogen and helium

Which region of the protoplanetary disk is the hottest?

the innermost region

The planets in our solar system are thought to have come from

the same cloud of gas and dust in which the sun formed.