Chapter 19 - Stars Flashcards
(33 cards)
What is a nebulae?
Gigantic cloud of dust and gas (mainly hydrogen), can be many many times bigger than our solar system
Do nebulae form quickly?
No, over millions of years
How do nebulae form?
The tiny gravitational attraction between particles of dust and gas, pull all the particles together to form a cloud
What happens as the dust and gas get closer together?
The gravitational collapse accelerates
How do denser regions form?
Due to tiny variations in the the nebulae, denser regions are apparent and these regions pull in even more dust and gas (only getting denser)
Why would the heat of the denser regions change?
They get hotter due to more gravitation energy being converted to thermal energy
What is a protostar?
One of the denser regions of a nebulae - very hot and very dense sphere of dust and gas
What must a protostar do to become a normal star?
Nuclear fusion must start in it’s core
What conditions are needed for nuclear fusion in a protostar’s core?
Extremely high temperatures and pressures to overcome the electrostatic repulsion between hydrogen nuclei
What do fusion reactions produce?
Kinetic energy
What happens for a protostar continuously gaining mass, so hot and provided enough KE to overcome the electrostatic repulsion?
Hydrogen nuclei are forced together to make helium nuclei, nuclear fusion begins, a star is made
How does a star remain in an equilibrium with a roughly constant size?
Gravitational forces compress the star, but the radiation pressure and gas pressure push the star outwards, balancing the forces out
Where does radiation pressure come from?
From the photons emitted during fusion
Where does gas pressure come from?
From the nuclei in the core
What is a star - in this equilibrium - stage of life called?
The main sequence
What effects how long a star stays on the main sequence?
The mass and size of its core, the more mass = the more power it releases and the quicker it undergoes fusion = shorter life
What stars are likely to have a shortish life?
Massive supergiants, much hotter and bigger than others
Description of a planet?
An object in orbit around a star, with three characteristics
Characteristic of a planet - concerning its mass?
It has a large enough mass so that its own gravity allows a spherical shape to form
Characteristic of a planet - concerning reactions?
It does not carry out nuclear fusion
Characteristic of a planet - concerning its orbital path?
It has most likely cleared its path of any other objects previously there e.g. asteroids
What is the difference between a planet and a dwarf planet?
Dwarf planets have not cleared there orbital paths of other objects unlike planets
Description of an asteroid?
Objects too small or uneven to be a planet, in near circular orbit around the sun (without the ice present in comets)
What is a planetary satellite?
Any body in orbit around a planet e.g. moons/man made satellites
