Our Galactic Neighborhood and Beyond
Have you ever played the address game? Here's how it goes:
I live at ______ (fill in your street address), which is in the city of ______ (fill in your city), which is in the state/province of _______ (fill in your state or province), which is in the ________ (fill in your country), which is in _______ (fill in your continent), which is on the planet _______ (Earth), which is in the _______ (solar system), which is in the ______ (Milky Way galaxy), which is in the ______ (Local Group of galaxies) within the ______ (Universe).
The sun warms us each and every day, but did you know that the sun is also a star and that all the stars in the night sky are suns themselves? And these stars, or suns, can have their own solar systems. There are hundreds of planets orbiting these far away stars.
Now think about galaxies. A galaxy is full of stars. Our sun is just one of at least 200 billion (!) stars in our own Milky Way galaxy. Just like our sun is one of many stars or suns, and our solar system is one of many solar systems, so is our galaxy. Our galaxy is in the the Local Group, a neighborhood of about 30 galaxies. And our nearest major neighboring galaxy is called Andromedea. The Local Group is also just a small piece of the Universe. There are believed to be hundreds of billions of galaxies in the Universe.
Our galaxy, the Milky Way, is spiral shaped, as are other galaxies in the Universe, but some are elliptical and a few look like toothpicks or rings. But how do we know what a galaxy looks like when the planet we live on is just a small part of the huge solar system that is one of many in the vast Milky Way galaxy? The Hubble Ultra Deep Field (HUDF) -- a very strong telescope -- can see beyond our galaxy and because it can, we have been able to see what other galaxies look like.
Now let's talk about dark matter. Dark matter is the opposite of bright matter. Bright matter is what we can see with our naked eye or with the help of telescopes -- bright objects such as planets, stars and galaxies. Dark matter is what exists around all those bright objects. We know it exists because we can detect its gravitational pull on other objects in the Universe -- we just can't see it. Some examples of dark matter are black holes and objects just a little too small to be stars (so they can't produce light of their own). We believe most of the dark matter is composed of new particles smaller than atoms that are different from anything scientists have ever detected or studied so far.
As you can see space is a vast place with many areas.
Watch this video to see an artist's conception of Earth within the Milky Way galaxy: Solar System Scale