Objective I Can Describe the Appearance and Apparent Motion of Groups of Stars in the Night

Objective –I can describe the appearance and apparent motion of groups of stars in the night sky.

Constellations

Youprobablyknowsome constellations. The Big Dipper looks like a giant pot with a long handle. Orion is named after a great hunter. You can see his belt, marked by three bright stars. Constellations are imaginary pictures in the sky.

Thestarslook like they are all the same distance away.That’s not true.The stars in the sky are different distances from Earth.

Which Constellation is Which?

Whenyoulookupatthe sky, you may see shapes.Ancient stargazers created these shapes.They are the constellations.They are named after people, animals, and things that were important to them

You can use a star chartthat shows where stars appear in the sky.As the night passes, these shapes seem to move through the sky.It’s Earth that’s moving, not the Sun and stars.It’s rotating on its axis.

Youcanonlyseethebrightest stars with the naked eye. Look at the stars through binoculars or a telescope. Thousands of fainter stars can be seen. You can no longer see the shapes of constellations.

Do Constellations Always Look the Same?

The Earth revolves around the Sun.This is why you see different constellations through the year.

• In the summer, we can’t see Orion because it is between the Earth and Sun.It is daylight.
• Six months later we can see Orion.It is on the side of Earth away from the Sun.

Peopleinthe Southern Hemisphere see different constellations than people in the Northern Hemisphere.

Southern Hemisphere Constellations Northern Hemisphere Constellations

Constellations shapes also change. It takes thousands of years for changes to be seen. They will look different in a hundred thousand years.

How Do Astronomers Use Constellations?

Astronomersdividethe sky into 88 constellations. Astronomers name objects after their constellation.The Andromeda galaxy and the Orion nebula are examples. Earth sometimes passes through showers of meteors. The showers are named after the constellations from which they seem to fall.The Perseids and the Geminids are two examples.

What Are the Constellations of the Zodiac?

TheBabylonians noticed the Sun’s position in the sky changes through the year. They divided the stars along the Sun’s path into twelve constellations. We call these twelve the constellations of the zodiac. (There are really thirteen!)

The constellation Ophiuchus (the Serpent Bearer) is the thirteenth.

The Moon and the planets appear to move through the constellations of the Zodiac. Here’s what the Moon might look like travelling through Leo.

Look at Saturn. We would say, “Saturn is in Leo.” Over six weeks, Saturn moves through Leo. When you see a planet, you will a couple of things. First, it will be brighter than the stars around it. And, it will not twinkle like the stars around it.

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