Lecture 8

Question 1

What is nebular theory?

Answer 1

Our solar system was formed from the collapse of a giant interstellar gas cloud

Question 2

What is galactic recycling?

Answer 2

• stars are born in clouds of gas and dust
• stars produce heavier elements through fusion reactions
• stars return elements to space when they die

Question 3

How does the conservation of momentum account for the speed of the contracting gas cloud?

Answer 3

The rotation speed of the cloud which our solar system formed must have increased as the cloud contracted

Question 4

What is flattening?

Answer 4

Collisions between particles caused the cloud to flatten into a disk

Question 5

What are the terrestrial planets?

Answer 5

Rocky, small planets close to the Sun

Question 6

What are the Jovian planets?

Answer 6

Gas giants further from the sun

Question 7

What is the conservation of energy in the birth of a star?

Answer 7

Gravity causes a gas cloud to contract. Due to the conservation of momentum the cloud speeds up. As the cloud speeds up, energy must be conserved and gravitational potential energy is converted to kinetic energy. The centre heats up and a star is born

Question 8

What is solar wind?

Answer 8

Once the sun formed the solar wind blew the non-accreted particles away.
Solar wind consists of charged particles- electrons and protons

Question 9

What is the frost line?

Answer 9

Between Mars and Jupiter. Inside the frost line it is too hot for hydrogen compounds to form ices.

Question 10

How did the terrestrial planets form?

Answer 10

Small particles of rock and metal were present inside the frost line. Planetesimals of rock and metal built up as these particles collided. Collisions and gravitational attraction eventually assembled these planetesimals into terrestrial planets

Question 11

How did the accretion of planetesimals occur?

Answer 11

Smaller objects collided to become larger ones

Question 12

How did the Jovian planets form?

Answer 12

Ice can form small particles outside the frost line. Larger planetesimals and planets were able to form. Gravity of these larger planets was able to draw surrounding H and He gases.

Question 13

How do we know our solar system is not made from primordial gas?

Answer 13

Given that there are many heavy elements in the solar system, the gas cloud must have gone through multiple stages of galactic recycling

Question 14

How is a solar system formed?

Answer 14

-a protostar arises from a cloud of gas collapsing
-a flattened disc forms
-the disc collects dust and produces structures that become the formation sites for planets

Question 15

How is the motion of large objects in the solar system similar?

Answer 15

-they have nearly circular orbits
-they all orbit in the same direction
-they all orbit almost in the same plane

Question 16

What is the effect of conservation of energy on the solar system’s formation?

Answer 16

-inner parts are hotter than outer parts
-rocks can be solid at higher temperatures so exist inside the frost line
-gases can be accreted due to the gravity of a larger body
-solar wind blew away non-accreted particles

Question 17

Why do the Jovian planets decrease in size moving out?

Answer 17

The gas cloud was less dense on the outside