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Flashcards in Chapter 19 - Stars Deck (33)
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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


Description of a comet?

Small irregular bodies made of ice/rock/dust, all comets orbit the sun in eccentric elliptical orbits, the release a gas 'tail' when near the sun


Description of solar systems?

Our solar system contains the sun, planets and any other objects that orbit either of these


What is a galaxy?

A collection of stars and interstellar dust and gas - a large amount of these stars have their own solar systems


Our galaxy?

The milk way


Vague description of our universe?

Electromagnetic radiation, energy, matter, space-time = everything


What is Orion?

One of the most recognisable constellations - containing stars at different points in their lifecycle