Starter: Explain how the idea of how the universe is arranged has changed over time? Why does it keep changing?? Practice: Notes ; glue here when done 3/2/ /2/16 Connection: Ws Exit: What does the color of a galaxy as seen from earth tell us? Galaxies Notes and Ws Application: Galaxies Notes and WS NumberType of Galaxy EQ: How can patterns be used to describe the universe?

1. Starter 2. Notes 3. Activity 4. Exit

DateLecture/ Activity/ Lab Page Table of Contents 2/29 Big Bang Lab /1 Em Spectrum /2 Galaxies Notes

 A galaxy is a collection of stars, gas and dust held together by gravity.  Scientists estimate that there are more than 100 billion galaxies scattered throughout the visible universe.  Galaxies range from 10,000 to 200,000 light-years in size. Galaxies

 Globular clusters-groups of older stars

 Gravity holds the billions of stars together, and the densest region is in the center, called a core or bulge.  All galaxies have a faint outer region or envelope and a mysterious dark matter halo.

 Quasars- star-like sources of light; may be cores of young galaxies

 Nebulas- large clouds of dust and gas; birth place of stars

 Altogether, a galaxy contains billions of stars and there are trillions of galaxies distributed across the Universe.  There are four main types, spiral, barred spiral, elliptical and irregular.

 Have a bulge in the middle and spiral arms  the center of a spiral is made of old stars,  arms made with young stars that formed recently out of gas and dust.  shape caused by the rotation of the galaxy  We live in the Milky Way, a Spiral Galaxy on the Orion Arm in the Local Group.

 Barred spirals have a round or oval bulge with a nearly rectangular bar across it.  The spiral arms attach to the bar rather than the bulge.  Two thirds of all spiral galaxies are barred spirals and after a certain amount of time, the bars disappear.

 Have no star formation or any visible features.  Most have thousands of globular clusters  Contain mostly old stars  Have bright centers and very little dust and gas  Looks like a sphere Elliptical Elliptical galaxies might be formed when two galaxies merge

 Mostly have grainy, highly irregular groups of bright areas.  They have no noticeable symmetry nor obvious central core  Made of younger stars  They don’t fit any other class  Found near spiral galaxies ▪ Ex. Magellanic Clouds Irregular

 The next 10 slides are different pictures of galaxies.  As we go through the pictures, in the chart in your journal, write down the name of which type of galaxy you think each picture is.  Try to get as many as you can correct.  We will review in the end.

Irregular

Barred Spiral

Irregular

Elliptical

Spiral

Irregular

Spiral

Elliptical

Barred Spiral

Starter: Explain how the idea of how the universe is arranged has changed over time? Why does it keep changing?? Practice: Notes ; glue here when done 3/2/ /2/16 Connection: Ws Exit: What does the color of a galaxy as seen from earth tell us? Galaxies Notes and Ws Application: Galaxies Notes and WS NumberType of Galaxy EQ: How can patterns be used to describe the universe?