Planets Flashcards
Define a planetary system.
a set of objects that orbit around a star. They form around the same time stars are.
How does a planet first form?
A clump within a stellar nebula collapses. This then forms a protostar with a disk. The clump carries on heating and rotating until the protoplanetary disk flattens out.
What “forms” in the disk?
Particles of dust clump together (accreted), which forms planetismals.
When the planetismals get big enough, they attract each other through gravity. Sticking together. Process continues until planets form. Rocky first then gravity.
Where do rocky planets and gaseous planets form?
Rocky planets form inside the frost line whereas gaseous planets form outside the frost line.
What happens when the star becomes a main sequence star?
The solar winds from the MS star stream out, pushing out any remaining dust out of the solar system. Preventing anymore planetismals to form.
Define a frost line.
A temperature line that separates the formation of rocky planets and gaseous planets.
Define accretion.
The accumulation of matter under the influence of gravity to form planets.
Describe the process of rocky planets forming.
- Planetismals form from the accretion of dust.
- Rocky and metallic planetismals form inside frost line.
- planetismals accrete and form rocky planets.
- Dense material formed at core, less dense material forms crust.
- H and He go beyond frost line.
- Atmospheres form around planet with enough gravity to hold onto them.
Describe the process of outer gas planets forming.
- Planetismals form from accretion of dust.
- Rocky, metallic, and icy planetismals form outside frost line.
- Planetismals accrete, forming gaseous planets.
- H and He attach by gravity.
- Rocky material sunk to centre of planet, forming the core.
- Ice and gas (H+He) are held by gravity around the planet.
What is the formation of the asteroid belt?
Jupiter’s gravity effected the orbits of some planetismals that were accreting during the time. As a result, they broke and formed asteroids. (Failed planets)
Asteroids have a highly irregular shape that weren’t big enough to be round.
How was our moon formed?
- A planetismal size of Mars struck Earth after the solar system formed.
- Large volume of heated material was ejected from object’s outer layers.
- Disk material formed, accreted and became the moon. (Explains why moon’s rock is similar to that on Earth.
Name the 3 ways moons can form.
- By collision
- From a circum-planetary disk.
- they are captured asteroids or Kuiper Belt objects (Which orbit the planet wrong way around).
