What do you know? Compared to the volume of Earth, the volume of the Sun is approximately (1) the same (2) 100 times greater (3) 1,000 times greater (4) 1,000,000 times greater (4) 1,000,000 times greater

The Universe The universe is made up of empty space, energy, and matter. Matter includes: Gas molecules (mainly Hydrogen) Dust particles

Matter can come together to form: Stars Planets Moons Meteors Asteroids Comets Some objects can be seen with the unaided eye. Telescopes are used to see most objects. The objects in the universe are in motion and moving away from each other.

Stars Stars: spherical masses of hot gases that produce heat and light energy. Measured in light years because they are so far away. Light year: the distance light travels in a year.

How bright a star appears depends upon: Distance from Earth The closer it is, the brighter it will appear. Size The bigger it is, the brighter it will appear. Temperature The hotter it is, the brighter it will appear. Most stars appear white to the naked eye, but stars come in different colors. E.g. the sun is yellow.

Stars are different colors depending on their surface temperature. The hottest stars are the color blue while the coolest stars are the color red.

Stars are classified based on their color and brightness.

Stars have a life cycle. This means they change over time. A stars complete life cycle can take many millions of years. When a star’s mass is used up, the star dies. Corny Star Joke

The Sun The Sun is the closest star to the Earth and is the center of our solar system. All other stars are OUTSIDE of our solar system. Even though they look so small, many are 100 or more times bigger than our Sun.

Our Sun is the color yellow. It is an average sized star. It is so large that about 1,300,000 planet Earths can fit inside of it

It is made up mostly of the gases hydrogen and helium. Its energy is created by the joining of two hydrogen atoms, also called fusion. The Sun’s energy reaches Earth as heat & light (radiation) When our Sun runs out of Hydrogen, it will lose its mass and become a white dwarf. Note: Our Sun is middle age. This means it is only half-way through its life cycle.

What are star trails? Star trails are pictures that show the path of a star in the sky. Stars do not actually move, but appear to move because the Earth rotates. This is called apparent motion. The actual trail of the stars can only be viewed by time lapse photography. This means that many pictures are taken over time, usually 24 hours.

All of these pictures are superimposed onto one final picture All of these pictures are superimposed onto one final picture. The final picture shows the path of the stars in the sky during the length of time of the exposure. Imagine that these pictures of three stars were taken over a period of one hour. Do you see how their location has changed?

If we take all of the pictures and “superimpose” them onto one picture it would look like this. The final picture shows the path of the stars over time. This is called Star Trails.

Star trails over a few hours.

This picture shows a time lapsed photo taken over a 24 hour period This picture shows a time lapsed photo taken over a 24 hour period. Notice how the middle does not appear to move? This is where the North Star (Polaris) is located. This is one of the reasons the North Star is special.

This is how star trails would appear if the Earth did not rotate.

Why is the North Star special? The North Star is special because it is located directly over the ________ pole. North For this reason, we never observe any apparent motion of the North Star.

The North Star is part of the Little Dipper.

If you observe the North Star from your yard, you will be able to If you observe the North Star from your yard, you will be able to observe it in the EXACT same spot tomorrow, in two weeks, and in 30 years. It will always be found in that same spot when you are in your same yard. Note: If you move, it may be located in a different location in the sky. It depends on WHERE you move to.

It can help you determine your location north of the equator! The North Star is always equal to your latitude in the northern hemisphere. Just look north, find the North Star, and determine its angular elevation. Its angular elevation is equal to your latitude! How can this help you? It can help you determine your location north of the equator!

imaginary line where the sky meets the land. Angular elevation measures the angle from the horizon to a star. The horizon is the _________________ ____________________________. imaginary line where the sky meets the land. This line is the horizon

Practice: Stand up and point to your horizon – this is zero degrees. Use your other arm to point straight over your head – this is 90 degrees. All angular elevations will be between zero and ninety degrees. 90 degrees Zero degrees

What is the angular elevation of the observer to the star shown in your notes? 90 degrees 45 degrees Zero degrees

Why can’t you see the North Star from the southern hemisphere? THINK ABOUT IT Why can’t you see the North Star from the southern hemisphere?

The Universe is made up of different types of Galaxies. Galaxies: Large groupings of millions or billions of stars and other forms of masses held together by gravity. Our solar system is in the _________ ______ ________. Milky Way Galaxy

The Milky Way

Elliptical Galaxy Shaped like a ball or slightly flattened ball.

Irregular Galaxy No definite shape Most common type of galaxy

Spiral Galaxy Shaped like a flattened disk with spiral arms. What Galaxy do you know of that is spiral?

Our Solar System is in the Milky Way Galaxy Our Solar System is in the Milky Way Galaxy. Approximately 100,000 light years from arm to arm. Our star is the _______. Sun We are here

17 years 69 times What’s a light year? Distance light travels in one year. We use this to measure the VAST distances in Space. Facts about Light Years: * How long would it take a commercial airplane to travel to the sun? __________. * How many times can you go from NY to San Francisco at the speed of light? __________. 17 years 69 times

Classify Each Galaxy Spiral Elliptical Irregular