Lesson 7 Flashcards
How much mass does the Sun contain?
The Sun contains 99.9% of all mass in the solar system
What is the sun made up of?
Hydrogen and Helium gas
Where is Mercury located? What is its size?
Mercury is located 0.39 AU from the sun; it is the smallest planet in the solar system
Where is Venus located? Describe why Venus is the hottest planet? What is its size?
Venus is 0.72 AU from the sun; it is so hot because Venus’ atmosphere traps heat from the sun; Venus has almost the same diameter as Earth
Describe Mars. Where is it located? What is its mass?
Mars is located 1.52 AU from the Sun; its mass is 10% tht of Earth & has two moons
Describe Jupiter.
- 5.2 AU from the sun
- largest planet in the solar system
- has 60+ moons
- has a long lived storm on its surface called the Great Red Spot
Describe Saturn.
- 9.54 AU from the sun
- approximately 60 moons
- has a ring system
Describe Uranus.
- 19.2 AU from the sun
- has an atmosphere of methane
- has a ring system
- 24+ small moons
Describe Neptune
- 30.1 AU from the Sun
- has dark rings
- is more massive than Uranus
Describe Pluto
- 39.5 AU from the Sun
- is a dwarf planet
Name two of Mars’ moons
Phobos
Deimos
What is Neptune’s largest moon?
Triton
What is comparative planetology?
The study of comparing planets
What kinds of questions does comparative planetology ask?
- Are all planets made out of the same materials?
- Which planets have solid surfaces?
- How can we group them to have common characteristics?
What are the four features of the formation of the solar system?
- motion of large bodies
- two major planet types
- swarms of smaller bodies
- notable exceptions
Describe the motion of large bodies in the solar system?
They orbit in an organized fashion, counter clockwise, in nearly the same plane
- they usually rotate in the same direction as the orbit
Describe the two major planet types?
- terrestrial planets
- have a small mass
- are closer to the sun
- have solid surfaced - jovian planets
- have a large mass
- are far from the sun
- surfaces are gas and not solid
Describe feature 3, swarms of smaller bodies?
- Asteroids (like small planets)
- Comets (made of ice)
- both orbit the Sun
Describe the notable exceptions to the patterns in the solar system?
- Venus rotates clockwise
- Uranus’ axis is tilted almost on its side
- Earth has a large moon compared to its mass
What are the two main theories for the four main features of the solar system?
- The close encounter hypothesis
2. The Nebular hypothesis
Describe the close encounter hypothesis? What are the problems with this theory?
This theory states that the planets formed from debris torn off by the sun by a close encounter with another star
- this theory can’t explain the observed motions and types of planets
Describe the nebular theory? In what way does it surpass the close encounter hypothesis?
The nebular theory states that our solar system formed from the gravitational collapse of a giant interstellar gas cloud; the shockwaves of a nearby star caused the gas to collapse (nebula)
- nebular theory explains all of the observed patterns that we see in the solar system
What is the solar nebula?
The proposed gas cloud which formed our solar system
What is galactic recycling?
stars are born in clouds of gas and dust > stars produce heavier elements from lighter ones > stars return material to space when they die > a new star is born
How does nebular theory explain the orderly pattern of motion of planets?
- as the solar nebula collapsed, it became very heated
- the nebula spun faster the more it shrank
- the solar nebula flattened into a disk
- the formation of the spinning disk forms the orderly pattern of motion in our solar system; all of the planets orbit in nearly the same plane because they all, at one time, existed in the plane of the flattened disk
What is condensation?
Materials other than hydrogen and helium can condense into solids at different temperatures
What is accretion?
solids collide and stick together, growing larger
What is planetesmal formation?
Accreted objects attract others through gravity, forming a piece of a planet (i.e. a planetesmal)
How does nebular theory explain why there are two main categories of planets?
- because of condensation, only rocky elements within the frostline could condense, while hydrogen stayed gaseous out of the frostline
- accretion occurred with both of these elements
- accreted objects attracted each other, forming planetesmals)
- gravitational encounters caused only the largest planetesmals to survive collisions
How does nebular theory explain the origin of asteroids and comets?
These are actually leftover planetesmals
What are asteroids?
Rocky leftover planetesmals of the inner solar system
What are comets?
Icy leftover planetesmals of the outer solar system
How does nebular theory explain the exceptions in the solar system?
- captured moons: occurred when passing planetesmals lost energy to friction in the gas that surrounded planets as they formed
- giant impacts caused Uranus’ tilt and why Earth has such a large moon
What is radiometric dating?
determining the age of a rock
What does a half-life describe?
The time for half the nuclei in a substance to decay
What does radiometric dating tell us about the age of the solar system?
That the oldest rocks on earth are 4.4 billion years old
- planets probably formed 4.5 billion years ago
- the oldest meteorites are 4.56 billion years old
