ASTRONOMY

In case you couldn’t tell, space is very, very, VERY big. EVERYTHING out there – stars, planets, etc….is called the UNIVERSE

STARS – large balls of superheated gas that give off all of the energy a planet needs. These are so far away we have to measure them in LIGHT YEARS – the distance light can travel in 1 year. (by the way, light travels 186,000 miles/second!)

Our galaxy – THE MILKY WAY

Our sun (Sol) is just one of billions and billions of stars in the galaxy. However, in terms of all stars, it is average size and brightness

In terms of our planets, it is 333,000 times as massive!

Our solar system is made up of the objects that revolve in orbits around the Sun.

This includes the sun (Sol) itself, all the planets, moons, comets, and asteroids.

The reason that objects are held in orbits is because of the immense gravity of the sun. Gravitational pull Gravitational pull is controlled by two things: 1.) MASS 2.) DISTANCE

Can you avoid hitting an object with a comet?

How did it all start? BIG BANG THEORY – all matter and energy were in a single point that exploded outward in all directions.

Much like a raisin in raisin bread - Other objects in the universe are moving away

How do we know? It wasn’t like we were there… 1.) Presence of BACKGROUND RADIATION

It’s like the Universe’s ears are ringing from the “bang”

2.) The DOPPLER EFFECT tells us that the universe is expanding. What is the Doppler Effect? In one word: NEEEEEOOOOOUUUUUMMMMM

As the object gets closer, the sound waves from it “stack up” – causing the pitch to increase

But there is no sound in space…so instead of having the sound pitch increase or decrease, the wavelength (color) of light will increase or decrease.

Objects moving away from an observer have the wavelength of light get LONGER – this makes the object look RED

Objects moving toward from an observer have the wavelength of light get SHORTER– this makes the object look BLUE Almost every object in the celestial sphere is moving away from us…meaning THE UNIVERSE IS EXPANDING

Once all the matter was thrown outward, it began to condense under the pull of gravity into stars, planets, etc…

BREAKDOWN OF THE PARTS OF THE UNIVERSE: 1.) Galaxies: a massive collection of stars, dust, planets 3 types: Spiral (the Milky Way), Elliptical, Irregular

At the center of each galaxy – a SUPERMASSIVE BLACK HOLE

2.) Stars: Superheated balls of gas held together by immense gravity. They produce energy through nuclear fusion – slamming two atoms together at high temps to make one, releasing massive amounts of energy

Luminosity of stars – how bright the star would be in our sky if it were located where the sun is. Brightness of stars – How bright the stars actually seems, factoring in luminosity & distance.

Stars are grouped into types based on temperature and luminosity. See ESRT.

Birth of stars:

How a star dies is dependent on its mass: Smaller stars will fade into white dwarves, and then into black dwarves.

How a star dies is dependent on its mass: Larger stars explode into supernovas, and then collapse into black holes