Y12 Stars and Planetary Systems Flashcards
(42 cards)
Define a planetary system.
a set of objects that orbit around a star. They form around the same time stars are.
Where does a planet first form?
In the protoplanetary disk. This forms when a clump in the stellar nebula collapses causing a protostar to form with a disk. The disk continues to flatten, heat up, and spin rapidly forming it.
What “forms” in the disk?
Particles of dust clump together (accreted), which forms planetismals.
What happens to the planetismals?
The planetismals continue to accrete. 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 in the solar system?
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 the outer gas planets’ formation.
- 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.
How did the asteroid belt form?
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 3 ways moons can be formed
- By collision
- From a circum-planetary disk.
- Captured asteroids or KBOs (orbit wrong way round)
Describe a Sun-sized star in its main sequence stage.
The longest and most stable part of the star’s life. Nuclear fusion occurs, H fused to He, which releases vast amounts of energy as heat and light.
What is a red giant?
After all the hydrogen is used up, a red giant forms. Helium now fused to Carbon and O in the hotter core. Core carries on contracting and heating up. Outer layers expand and cool. The star is red because it is cooler, but it has a high luminosity due to its size.
What happens at the core of the star?
In the hot and dense core, nuclear fusion occurs. Releasing vast amounts of light and heat.
What is the outer shell of a star?
Photosphere: it is made up of H and He hot gas. This shell helps move heat from the core to the surface of the star. Heat and light released into space.
What is hydrostatic equilibrium?
It is what keeps a star stable. The balance of gravity pulling a star’s atoms to the centre and outward pressure of heat and light radiating.
Describe giants and supergiants
Giants and Super-giants:
* When stars run out of H they become giants and supergiants.
* Core becomes hotter and denser - more than 1.4 Msun
What is a white dwarf star?
A small, very dense, hot star mostly made of carbon. It’s what remains after a red giant loses its outer layers.
What are red dwarf stars?
Red dwarves are the smallest kind of star on the main sequence and have the lowest temperature of the catefory.
Fuses H to He only
Brown dwarfs?
Brown dwarfes are considered failed stars that never acheived nuclear fusion in their core.
How are stars organised by their color and temperature?
They are organised through spectral classes. Organised by spectral type hottest to coolest: OBAFGKM. (Oh Boy An F Grade Kills Me)
Small, cool K and M class stars are the most common. Whereas large and very hot stars are rare.
What is apparent magnitude?
How bright a star appears to us from Earth.
