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The Structure of Galaxies - 6th Grade

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William Begoyan

on 8 April 2016

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Transcript of The Structure of Galaxies - 6th Grade

The Structure of Galaxies
By: Mr. Begoyan
Page 51 in ISN
What is a Galaxy?
A
galaxy
is a gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter.
Galaxies range from dwarfs with just a few thousand stars to giants with one hundred trillion stars, each orbiting their galaxy's own center of mass.
Many galaxies are believed to have black holes at their active center. The Milky Way's central black hole, known as
Sagittarius A-star
, has a mass four million times that of our Sun.
There are approximately 170 billion galaxies in the observable universe.
Types of Galaxies
Galaxies come in three main types:
elliptical,

spirals
, and
irregular.
An
elliptical galaxy
is a type of galaxy having an ellipsoidal shape and a smooth, nearly featureless brightness profile.
They are three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.
Spiral galaxies
consist of a flat, rotating disc containing stars, gas and dust, and a central concentration of stars known as the bulge.
The spiral arms are sites of ongoing star formation.
A super massive black hole exists at the very center of the central bulge
An
irregular galax
y is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.
They are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.
A
peculiar galaxy
is a galaxy which is unusual in its size, shape, or composition.
Peculiar galaxies come about as a result of interactions between galaxies
A
lenticular galaxy
is an intermediate between an elliptical galaxy and a spiral galaxy.
A
barred spiral
galaxy is a spiral galaxy with a central bar-shaped structure composed of stars.
The Milky Way, is classified as a spiral barred galaxy.
The lives of galaxies
Galaxies formed about 400 million years after the creation of the universe.
Billions of galaxies were clustered close to each other at that time.
Galaxies are formed through gravity, and the larger they grow, the more matter they attract.
Clustering and merging is how galaxies gain mass, and can also determine their shape and structure.
Some galaxies are located in tight clusters.
Young galaxies with high amounts of gas can go through a
starburst
, a short period of extreme star creation.
Some galaxies will collide with others, generally resulting in a new, larger galaxy.
As galaxies age, they will grow smaller and dimmer.
Question set 1
Questions Set 2
1. What is a galaxy?
3. What are you likely to find in the center of many galaxies?
2. Are galaxies about the same size?
4. Approximately how many galaxies have we observed?
5. What is the difference between a spiral and elliptical galaxies?
6. What is the difference between a lenticular, spiral, and barred spiral galaxies?
7. What is the difference between an irregular and a peculiar galaxy?
8. What happens to galaxies as they live their long lives?
Homework
On page 50 of your ISN describe and visualize the 3 main types of galaxies.
Full transcript