StarStories 6 th Grade Astronomy

The Stars in Ancient Times People have looked at the sky for thousands of years. When ancient people looked up, the stars looked almost identical to what we see today. Stars do change, but they change VERY slowly. We will probably not notice changes to the stars in our lifetime.

Viewing Stars and Planets These ancient people did not have the same technology and tools that we have today. But they were able to notice the difference between stars and planets. What do you think they saw in the sky that told them that there was a difference? Copernicus – One of the first astronomers that believed in a “heliocentric” system. Helio = sun…so a system that moves around the Sun. Before that, people believed in a “geocentric” idea. Geo = Earth…so Earth at the center.

A Whole Lot of Movement First, we need to remember that Earth is doing A LOT of moving around. In this satellite photo, we can see the line of light and shadow that makes day and night.

Rotation Earth rotates on its axis. Part of the Earth faces the sun, while the other part of Earth is in shadow. Earth’s rotation is why we have night and day.

Revolution Earth revolves around the sun. The path that Earth and other planets follow is called an orbit.

Planets Moving All the planets do the same thing, but some planets take less time than Earth to travel around the Sun, while some planets take longer. But this is different than the stars…

Star Movement The stars do not travel around our Sun, which is also a star. BUT, we need to remember that our solar system is on the edge of the Milky Way Galaxy…which IS moving in space.

Star Movement So why do you always hear that the stars don’t move? It’s because we are traveling together in a group and the stars’ positions stay the same in that group….while the planets move around the stars. The stars appear to move because the EARTH is moving.

Earth’s Rotation Stars appear to travel in the sky in the same direction as the sun— from east to west. This is because our Earth is spinning the opposite—the Earth spins west to east—or counterclockwise.

Earth’s Rotation Here is another animation of the Earth rotating.

Earth and Stars -- Opposite Pretend you are standing looking at the night sky… The Earth movement is shown with a blue arrow. This makes the stars seem to be moving the direction of the red arrow.

Earth and Stars -- Opposite Here is a video that shows a time-lapse video of the night sky. You will see the stars moving from left to right (east to west). Remember, the Earth is actually moving west to east.

Milky Way – Not Just a Candy Bar In the video, did you notice a collection of cloud-looking formations? This is actually our galaxy…the Milky Way. Our Solar System is at the edge of the Milky Way.

Back to the Ancients Ancient people tracked the stars. They noticed that the stars stayed grouped together in the sky. They began grouping the stars in patterns, called constellations, and making up stories about them to help people remember.

But Wait!! There were “ancient” people in all different parts of the world. Some lived on the top half of the Earth, while others lived on the bottom. Would they see the same thing in the night sky? Talk to a partner about your thinking…

Hemispheres of Earth The Earth is divided into two hemispheres. The equator is the widest part of Earth. Above the equator is the Northern Hemisphere. Below the equator is the Southern Hemisphere.

View from the Hemispheres Stars are not just “above”…they are everywhere, and every direction. If we live in the Northern Hemisphere, we can only see part of space. We can’t see some of the same stars as the people on the Southern Hemisphere.

Northern Hemisphere This Skymap or Skychart shows the constellations visible in the Northern Hemisphere. However, what you can see depends a little on where you are in the Northern Hemisphere.

Southern Hemisphere The constellations in this skychart probably don’t sound as familiar. That’s because we can’t view most of them from the Northern Hemisphere….maybe just the ones at the edge. Why?

Compare Hemispheres What things do you notice when we compare both charts?

Pole Star The Southern Hemisphere seemed jam-packed with stars toward the middle. But the Northern Hemisphere has one thing the Southern Hemisphere doesn’t…a “Pole Star” Polaris – Our Pole Star

Pole Star Polaris (aka, the North Star) is almost directly above the North Pole. When the Earth rotates, Polaris does not appear to move like the rest of the stars. In fact…all of the stars seem to circle Polaris. Look at the Star Trail photo. The camera was left on to record the movement of the stars. The North Star doesn’t appear blurry or have a trail because it is in the same position the whole time. Polaris is at the center!

Polaris Ancient people used Polaris to help them find their way. Since Polaris appears in the same spot in the sky, they could tell which way was north.

How to Find Polaris First, you need to find the Big Dipper. The Big Dipper is not a constellation itself. It is an asterism. An asterism is a group of stars that are part of another constellation. The Big Dipper is part of Ursa Major (the Great Bear). It is fairly easy to find in the sky. The Big Dipper

How to Find Polaris The Big Dipper could be facing any direction. The Big Dipper

How to Find Polaris It could be going up and down.

How to Find Polaris It could be leaning.

How to Find Polaris It could be upside down.

How to Find Polaris Which ever direction it is facing, find the two end stars in the cup of the dipper. The Big Dipper

How to Find Polaris Follow them away from the Big Dipper

How to Find Polaris The bright star across from the cup of the Big Dipper is Polaris.

How to Find Polaris Polaris is in the constellation Ursa Minor….or commonly known as the Little Dipper.

Ursa Major The Big Dipper, an asterism, is part of a larger constellation called Ursa Major.

Ursa Major Ursa means “bear” and major means “great”. Great Bear….can you see the bear in this picture?

Constellations There are many other constellations in the sky. Though we usually talk about the constellations with their Greek and Roman names and stories, people of many different cultures had their own names and stories to go with the patterns they found in the stars.

Cassiopeia Another constellation across from Ursa Major and past Ursa Minor is Cassiopeia.

Circumpolar Constellations Some constellations can be seen all the time, no matter what time of year. These are called “circumpolar” constellations…around the pole.