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Transcript of Galaxies
A galaxy is made of hundreds of billions of stars and enough gas and dust to make hundreds of billions more stars. Galaxies are also made of x10 more dark matter than all the stars,and potential stars and it's all held together by gravity. They can also be as large as 200,000 light years in length.
What happens when galaxies collide?
The Milky Way
The Milky Way is our home galaxy. It's a disk about 120,000 light years across and in the middle is a bulge with a diameter of 12,000 light years. The disk is far from being flat. The Milky Way has a halo of dark matter that makes up about 90% of it's mass, but the halo is invisible. The Milky Way has over 200 billion stars but it's a middle weight galaxy. It didn't always look like it does today this is because our galaxy is eating other galaxies. Including the galaxy closest to us that will someday collide with ours. This galaxy is the Canis Major Dwarf galaxy. Our galaxy is 13.6 billion years old. That's almost as old as our universe itself.
By: Emily and Sybella
Scientist don't have a definite theory of how galaxies are formed but they have two theories.
1. Small particles slowly came together and formed stars, which then formed star clusters, which then formed galaxies.
2.The Universe was organized as huge clumps of matter that later divided into galaxies.
How do Galaxies form?
Different types of galaxies
Spiral galaxies look like a flat disk with a bulging center and a surrounding spiral. The older stars go to the bulge in the center of the galaxy. It spins at a hundreds of kilometers per second.
Elliptical galaxies are round and they look like a halo, but stretched longer on one side of the axis than the other. They contain up to one trillion old stars. The older stars go to the center just like the spiral galaxies, but they move in random directions. Few new stars are known to form in Elliptical galaxies, they are also the biggest type of galaxy.
Irregular galaxies are not like elliptical or spiral galaxies. They are shaped weirdly and have a lack of form because they are in the gravitational influence of other galaxies that are close by. They are also irregular because two galaxies have merged to form one galaxy.
-What is a galaxy made of
-How do galaxies form
-What are Elliptical galaxies
-What are Spiral galaxies
-What are Irregular galaxies
-The Milky Way
How do Astronomers know how far away
other galaxies are?
Astronomers measure the distance to galaxies by trying to find stars in other galaxies who's light output they can measure. Then they are able to determine how far away the galaxy is by observing the brightness of stars. They can also tell if there is a planet in the galaxy if the star blinks, this means that a planet is orbiting the star.
The word "galaxy" comes from the greek word galaxias which means "milky". This is a reference to our own galaxy, the milky way.
NASA Spitzer (guys Youtube channel)