At the end of each chapter you will see a section Quick Quiz. One third to one half of the test will be these questions. Chapter 1
The definitions of Astronomical Objects, Units and Motions on page 6
Astronomical units is earths average orbital distance (150 million km), ecliptic plane is Earth’s orbital path which is defined by a flat plane, and the axis tilt is earths tilt that is 23.5 degrees from a line perpendicular to the ecliptic plane.
Astronomical Objects: * star- a large, glowing ball of gas that generates heat and light through nuclear fusion in its core * planet- a moderately large object that orbits a star and shines primarily by reflecting light from its star. * Moon- an object that orbits a planet * Asteroid- a relatively small and rocky object that orbits a star * Comet- a relatively small and ice rich object that orbits a star * Small solar system body- an asteroid, comet, or other object that orbits a star but is too small to qualify as a planet * Solar system- the sun and all the material that orbits it. * Star system- a star and any planets and other materials that orbit it * Galaxy- a great island of stars in space, containing from a few hundred million to a trillion or more stars, all held together by gravity and orbiting a common center * Cluster of galaxies- a collection of galaxies bound together by gravity. * Super cluster- a gigantic region of space where many individual galaxies and many groups and clusters of galaxies are packed more closely together than elsewhere in the universe * Universe- the sum total of al matter and energy * Observable universe- the portion of the entire universe that can be seen from Earth * Light year- the distance light can travel in 1 year, 9.46 trillion kilometers * Rotation- the spinning of an object around on its axis * Orbit- the orbital motion of one object around another. * Expansion- the increase in the average distance between galaxies as time progresses
The universe is expanding and how we know this: The entire universe is expanding, meaning that average distances between galaxies are increasing with time. this fact implies that galaxies must have been closer together in the past, and if we go back far enough, we must reach the point at which the expansion began. We call this the Big Bang Theory, which occurred 14 billion years ago.
Hubble’s law: mathematical expression of the idea that more distant galaxies move away from us faster
The further away we look in distance, the further back we look in time is because light takes time to travel through space. We se things in the sky not as it is today but how it was.
The observable universe is the portion of the entire universe that we can potentially observe. We have no hope of seeing or studying anything beyond the bounds of our observable universe.
Raisin Bread analogy: the entire universe is expanding. Imagine a basic raisin cake in the oven, with raisins 1 cm apart. Place the cake into the oven, where it expands as it bakes. After an hour, you remove the cake and the raisin has expanded so that the distance between adjacent raisins has increased to 3 centimeters. The fact that the cake is expanding means that all raisins are moving away from the Local Raisin, with more distant raisins moving away faster.
Earth is not the center of the universe but instead a planet orbiting a rather ordinary star in the Milky Way Galaxy.
Cosmic distances are literally astronomical, but we can put them in perspective with the aid of scale models and other scaling techniques. Chapter 2 constellation: A constellation is a region of the sky with well defined borders: the familiar patterns of the stars merely help us locate the constellations. The names and border of the 88 official constellations were chosen in 1928 by members of the International Astronomical Union. Most…