9/4/12 - 9/7/12 What are constellations? by Mr. Battaglia

I will make the first post on our class blog as an example of what you will be doing on your assigned week. Here is the post for our first week of school.

Constellations are grouping of stars in space that people through history have connected to resemble various figures, animals, mythological creatures, people from stories, etc. Constellations are not real, they are simply an easier way for humans to identify the stars that are visible in the night sky. Trying to tell which star is which is hard. The constellations help us by breaking up the sky into more manageable bits. Constellations change their position in the night sky because the Earth rotates on its axis. As the Earth rotates on its axis the constellations appear to rotate in the night sky. It's not really the constellations that are moving but actually the Earth rotating! Some constellations are visible throughout the year, these are called circumpolar constellations. Northern circumpolar constellations are those constellations centered around the North Star and can be seen from anywhere in the northern hemisphere because they are "above" the north in space. Other constellations are visible only during certain months or seasons, these are called seasonal constellations. Seasonal constellations are visible only at certain times of year because as the Earth revolves around the Sun it changes our view of the night sky and what we see at nighttime.

http://www.windows2universe.org/the_universe/images/starmaps/map_1_large.jpg
This image shows the northern circumpolar constellations

One of the activities that we did this week was use a star wheel or star finder to figure out what constellations are visible in the night sky and where they would be located by date and time. By setting the star wheels to the correct date and time we can see which constellations are visible and where we should look in the sky to locate these stars. As I rotated the star wheel I was able to see how it appears the constellations are rotating in the night sky around the North Star, really it is the rotation of the Earth causing this. Another activity we did this week was draw our first Star Set. The first star set included many of the northern circumpolar constellations, including the little dipper, big dipper, and cassiopeia. It helped just to learn a few constellations at a time and learn the mythology of them. I thought it was interesting to learn that you can use the pointer stars of the big dipper to locate the north star.

This image shows the pointer stars of the big dipper pointing to the North Star, Polaris
http://astrobob.areavoices.com/astrobob/images/Polaris_map.JPG