Today’s Agenda… Bellringer: How are comets and meteorites different? Which one do we refer to as a shooting star? Review yesterday’s topics Notes on Galaxies and the Universe
Today’s goals…
Galaxies and the Universe Study Pack #12
What is a galaxy? A galaxy is a group of stars, gas, and dust held together by gravity Different shapes and sizes
Types of Galaxies Elliptical Spiral Irregular Named for their shape Page 460
The Milky Way Galaxy Spiral galaxy Hundreds of billions of stars Everything revolves around the center of the galaxy including the sun Figure 26 – Why is it called the Milky Way galaxy?
The Universe As many as 100 billion galaxies might exist All of the galaxies with all their stars make up the universe Page 463, Figure 28 – hundreds of galaxies in one part of the sky Think about how small Earth is in comparison to the universe!!!!
Measuring in Space Astronomical Unit Can measure distances between planets Equals 150 million kilometers (average distance form the sun to the Earth) Abbreviated AU If something is 3 AU away from the Sun it is 3 times farther from the sun than Earth is
Measuring in Space Light Years Can measure distances between galaxies It is the distance light travels in one year, about 9.5 trillion kilometers Page 462
Assignment…. Page 468 #1-15