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J. S.

on 26 October 2015

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Transcript of Galaxies

The Formation of a Galaxy
Life of a Galaxy (continued...)
Galaxies are HUGE collections of stars held together by gravity.
Do Galaxies Die?
It is widely believed that the center of most galaxies, including our own, contains a SUPERMASSIVE BLACK HOLE.
Formed by the violent deaths of those early, massive stars.
Everything in a galaxy theoretically revolves around this supermassive black hole. Therefore, it's possible a galaxy could "die" when everything has been pulled in billions to trillions of years down the road...
Soon after the Big Bang, it was common for galaxies to collide.
Therefore, there were many irregularly-shaped galaxies early on.
Galaxies continue to generally move outwards from the Big Bang.
Types of Galaxies
Our Galaxy: The Milky Way Galaxy
Our Sun is just one of 200 B to 600 B stars that make up the Milky Way Galaxy.
Relative Size: If our solar system (Sun + Planets) is the size of 1 quarter, our galaxy would be about the size of 1/3 of the US.
Diameter = 100,000 light years across! (That means it takes light 100,000 years to cross the galaxy!)
What are Galaxies?
Supermassive Black Holes
After a certain amount of time, it is likely that the stars that make up a galaxy will die, leaving brown dwarfs, black holes, etc.
However, exploded layers of stars can form new nebula to make new stars...
So the overall life of a galaxy probably lasts much longer than the life of its original stars.
3 general categories in the Hubble Classification Scheme:
Spiral Galaxies
Elliptical Galaxies
Irregular Galaxies

These categories are based on the apparent shape of a galaxy - how it looks to us from our perspective.
For example, we may not consider a spiral galaxy a spiral galaxy if it's viewed on its side and we can't verify the spiral shape.
Milky Way's Future?
Andromeda Galaxy and Milky Way Galaxy are on a collision course!
Some astronomers theorize the space between stars in a galaxy is so vast that the majority of stars and their solar systems (planets) are not likely to be affected. Others theorize that numerous starts will indeed be ejected away from the galaxies.
Stay tuned in about 3-5 billion years to find out...
The original Hubble Deep Field image was made of a series of 342 images taken by the Hubble Space Telescope over 10 days in 1995.
Looking towards the constellation Ursa Major (Great Bear)
About 3,000 objects in the image; almost all of them are galaxies.
The HUBBLE ULTRA DEEP FIELD was made from images taken between 2003-2004 and looks back in space/time about 13 BILLION YEARS! This image contains approximately 10,000 galaxies!
What am I???
Just how many stars are in a galaxy?

* Millions of stars (in dwarf galaxies)
* Billions in our own galaxy
* TRILLIONS of stars (in giant galaxies).
Not much is known, but here is what we can observe:
Galaxies formed soon after the Big Bang.
Massive stars formed in the center.
Matter is collected by GRAVITY and the galaxy grows.
Early massive stars die quickly and the resulting supernovas distribute material throughout the galaxy, seeding new stars.
Our View of the Galaxy
And now...The Hubble Ultra Deep Field!!!
Keep in mind:
The amount of space in this image is equivalent to holding a tennis ball 100 meters (about a football field's length) away!!!
In other words, this is about
1/13,000,000 of the sky!
Full transcript