1. Chapter 1

2.  Astronomy is the study of the stars and planets  The key to this course is to understand how we are a part of the vast universe

3.  One major key to astronomy is understand scale  Open your book to pages 2-3 ▪ Figures 1-1 thru 1-4 show just how scale works  The scale of space is extremely large so we will use scientific notation to help shrink some of these numbers  Astronomers also came up with the astronomical unit (AU)  Average distance from the Earth to the sun

4.  Our solar system consists of the sun, all of the planets and their moons, and all other space debris http://en.wikipedia.org/wiki/File:Solar_System_size_to_scale.svg The sun is 109 times larger in diameter than Earth

5.  Planets orbit around the sun in an elliptical (more oval than round) shape  The closer to the sun the smaller the orbit  Pluto’s orbit is extremely elliptical and this is one reason why Pluto has been declassified as a planet

6.  The book defines a planet as a nonluminous object larger than a comet or asteroid that orbits a star  This definition has been changed to a celestial body which is in orbit around the sun, has sufficient mass to assume hydrostatic equilibrium (a nearly round shape) and has “cleared the neighborhood” around its orbit

7.  Another unit of distance is the light-year  A light-year is the distance that light travels in a year, which is roughly 63,000 AU

8.  When we look out into space we are actually look at the past  It takes time for the light we see coming from the stars to actually get to us  Nearest star to Earth (other than the sun) is Proxima Centauri, which is 4.2 ly away  So if you look at this star you really are looking at what it looked like 4.2 years ago

9.  Galaxy is a great cloud of stars, gas, and dust bound together by the combined gravity of all the matter  Our galaxy is the Milky Way galaxy – if you look up during a clear night you should be able to see the Milky Way

10.  What is the most important thing you need to grasp before we move on to other chapters?

11. Missed Vocab  Star – A celestial object composed of gas held together by its own gravity and supported by nuclear fusion occurring in its interior  Milky Way – the hazy band of light that circles the sky, produced by the combined light of billions of stars in our Milky Way Galaxy  Milky Way Galaxy – the spiral galaxy containing the sun; visible at night as the Milky Way  Planet - nonluminous object larger than a comet or asteroid that orbits a star  Solar System – the sun and the nonluminous objects that orbit it, including the planets, comets, and asteroids

12.  Page 8  Review Questions 1-4, 7-8, 11  Problems 1, 4