Science Buddies: "Ask an Expert"

I did the experiment "Changing Constellations". I'm still confused about the word "change". Does change and move in this project mean the same thing? Or are we saying constellations don't change but the earth rotates and depending on where your location is determines whether they moved a distance to the eye? I'm confused when reading the charts, also.

The experiment is designed to show you how the starts appear to move (or not move) across the sky as the earth rotates about the earth's axis and as the earth rotates around the sun.

Can you clarify what questions you have about the charts?

LovingStars wrote:Or are we saying constellations don't change but the earth rotates and depending on where your location is determines whether they moved a distance to the eye

Exactly! While constellations do not actually move, they seem to, resulting in the apparent motion mentioned by Bill in the previous post. Other interesting things to note about constellations are that 1) they seem to rise in the east and set in the west, much like the sun, and 2) they change as seasons change, which again goes back to the role of Earth's own movement.

Hope this helped!

Adding on to the great inputs already provided by the other experts here us a bit more on what causes the apparent motion.

Goldenzenith wrote:1) they seem to rise in the east and set in the west, much like the sun

This is caused by the rotation of the Earth about It's North-South axis, which of course, is ~24hrs. Earth rotates toward the East at approximately 15 deg per hour. The same phenomena that makes it seem the sun (and stars) move across the sky almost 15 deg from East to West every hour.

Goldenzenith wrote:2) they change as seasons change...

Caused by the fact that the Earth orbits the sun on a yearly, ~365 day, trek. So if you observe the same stars on two occasions 10 days apart, the Earth will have moved in its orbit about the sun by almost (but not quite) 10 deg, affecting the aspect angle of you to the stars just slightly.

Also, the Earth's axis is tilted which can have an effect, but I won't go into that here...

Hi Astronomy,
I used to track the movement of planets in the sky using a telescope and a program called "Stellarium" to assist me.
You may want to look into downloading this program for a nice 3D view of the night sky on your computer.
There are buttons in the program to label and connect the stars in the constellations.

Good luck,
matthew