Where are we?

Milky Way Galaxy

Left is a picture of the real Milky Way taken by the satellite COBE. The disk and center region of our Galaxy are readily recognizable. This image makes the Milky Way appear much more galaxy-like and less like the smudge of stars we see stretching across our night sky. It is possible to imagine what our Milky Way might look like looking down on it from outside.

Because we dwell within the Milky Way Galaxy, it is impossible for us to take a picture of its spiral structure from the outside. But we do know that our Milky Way has a spiral nature from observations made from within our Galaxy (though whether or not it is a barred spiral is still being debated). To represent this, the beautiful spiral galaxy Messier 74 was used, as it thought to be a similar galaxy to ours.

Where we are located within our galaxy.• a spiral galaxy with large concentration of stars in

its nucleus • Stars, dust, and gas fan out from the thick center

of the Galaxy in long spiraling arms • Our solar system is located on one of these spiral

arms, about 26,000 light years from the center of

the Galaxy • All objects in the Galaxy revolve around the

Galaxy's center • Scientists have calculated that are about 400

billion stars in our galaxy

• Through a telescope the Milky Way galaxy has been found to be made up of countless individual stars that seem relatively close together. This is because from the vantage point of Earth we are looking at the Milky Way on its edge and can't see where the stars are actually located.

• The Milky Way is part of a galaxy cluster that includes 30 other galaxies, the closest of which is the Andromeda Nebula.

Our Solar System• Our sun is a medium large size star in our galaxy. It gives us heat and light.• Earth is the 3rd planet from the sun; about 93,000,000 miles away.• We are the 5th biggest planet in our system. Jupiter is the biggest.• Earth travels 595 million miles around the sun each year. Its orbit is an ellipse, which is

a long oval shape.• As it travels around the sun, it also rotates around its own axis. So, even though the

sun appears to be moving across the sky, it is our earth that is turning and moving instead.

Seasons and Axis Tilt• It seems as though the seasons are caused by how far we

are from the sun.• In reality, it is how we are tilted towards the sun that gives

us our seasons.• As the earth rotates around the earth, it maintains the same

angle of 23.5°.• The Northern and Southern Hemispheres have opposite

seasons from each other. We will only discuss the Northern Hemisphere where we live.

• In summer, the sun’s rays hit the earth at a more direct angle giving us a warmer temperature and more hours of light.

• During winter, the rays hit the earth at a more extreme angle resulting in cooler temperatures and fewer hours of light.

• Solstices– When the sun reaches its farthest northern and

southern delinations.– Summer Solstice is June 21st - longest day– Winter Solstice is December 21st – shortest day

• Equinoxes– When days are equal in hours per day.– Spring Equinox is approx. March 21st

• Autumn Equinox is approx. September 21st

Pacing our Solar System

• Stay together outside• Listen to Michelle• Fill out worksheet as we go along• Follow Directions