A PRESENTATION BY: BIJOY BABU

WHAT IS A GALAXY?A Galaxy is basically a large group of stars, gas and dust held together by gravity. This is the simplest definition of a galaxy.

What are the types of galaxies?: SizeSo we know what a galaxy is but there are different

types of galaxies. When we look through a telescope we see odd looking galaxies and normal

looking galaxies but we don’t really know there sizes. A small galaxy might have minimal of up to a couple thousand stars. People might think that is a lot but it is nothing compared to our galaxy and the mega galaxies. Our galaxy, the Milky Way has some

200 billion stars all together. The biggest galaxies out there have more than a trillion stars. Now that is just huge. You can also see how big galaxies are

by their age. Younger galaxies tend to have less stars than the old giant galaxies.

What are the types of galaxies?: ShapeThe next galaxy are the Elliptical galaxies. Elliptical galaxies are the most giant galaxies out of the 4 and scientist say they are formed by 2 other galaxies colliding with each other to give it a big size and that odd type of look:

The last galaxy we will see today is the irregular galaxy and from its name you can tell it has no shape at all. They are the most uncommon but are famous like the Cat’s Eye galaxy and the M82 which is both a starburst and irregular galaxy:

What are the types of galaxies?: Shape There are 4 types of galaxies in our universe. We start out with our own galaxy the Milky way. The Milky Way galaxy is a barred spiral galaxy which means that it has the shape of a disk with a bulge sticking out of it and a bar. It looks something like this:

The second type of galaxy in our universe is called a spiral galaxy. Spiral galaxies are the most common out of the 4 and they just look like a spiral shape but with no bulge in the middle.

The Milky Way as you know is our galaxy and home that we live in. It is home to at least 200 billion stars and is considered

a “giant” type of galaxy. Our galaxy is considered a Spiral Type of galaxy because of its spiral spinning shape and the big

bulge in the middle. The center of our galaxies (which is called the Galactic Center), like most galaxies contain more

stars than the outer parts. In the center is the main star Sagittarius A* which scientists are confident it is a super

massive black hole and just recently found out that there are super massive black holes in the center of every galaxies.

The Milky Way is the only galaxy to be recorded to have a planet with life, although there are billions of galaxies out there, earth is the main one. Scientist have found the age of the Milky Way, since our Sun is about 5 billion year old, the galaxy is at least 5 billion more years old (So roughly

about 10 billion years old) Our Milky Way is between about 750 billion-1 trillion solar masses and is about 10,000 light

years in diameter. Our galaxy is very unique and we are lucky to have it. From earth to the solar system, all the way

to the black hole. Our galaxy is changing every day.

•"Galaxies." SEDS. N.p., n.d. Web. 27 Jan. 2011. <http://seds.org/messier/galaxy.html>. • "NASA - Our Solar System." NASA - Home. N.p., n.d. Web. 27 Jan. 2011. <http://www.nasa.gov/topics/solarsystem/index.html>. • "The Milky Way Galaxy." SEDS. N.p., n.d. Web. 27 Jan. 2011. <http://seds.org/messier/more/mw.html>.