Unit 8: Stars, Galaxies, and the Universe

I. Scaling the Universe a.Universe: all of space and everything in it b.Due to such large or small numbers that astronomers often have to deal with, they work with scientific notation to give measurements i. Example: Write 1,500 in Scientific Notation ii. Example: Write 148,000 in Scientific Notation

I. Scaling the Universe d. Scale Drawing of Earth, Sun and two Stars

II. Star Systems and Galaxies a.A star is a giant ball of gas i. Mainly made of hydrogen and helium which is undergoing nuclear fusion ii. Example: Sun b. A planet is an object that orbits a star and is affected by gravity c. Stars are much larger and hotter than planets i. Example: The sun is 100 times larger than the Earth. In other words, if the sun were hollow you could fit 1 million Earth’s inside

II. Star Systems and Galaxies d. A Solar System has a star with orbiting planets i. they are also called planetary systems e. Our solar system i. The farthest planet in our solar system is Neptune ii. Some planets are rocky and metallic iii. Others are mostly liquid and gas iv. The outer planets are much larger than the inner planets

II. Star Systems and Galaxies f. Most stars are members of groups of two or more stars, called a Star System i. A Star System with two stars are called binary stars ii. If you lived in a binary star system you would see two suns in the sky iii. One is larger and brighter than the other in most cases iv. A large group of stars is called a star cluster

II. Star Systems and Galaxies g. A galaxy is a huge group of single stars, star systems, star clusters, dust and gas that is bound together by gravity i. Our galaxy is about 100,000 times larger than our solar system

CharacteristicObject Contains Gas Contains Liquid Made of Rock Consists of Multiple objects Undergoes Nuclear Fusion

Put these in order from largest to smallest, put a 1 beside the largest object and 4 will be beside the smallest object – The Sun_____ – Venus_____ – The Milky Way_____ – The Sol System (the name of our solar system)_____

II. Star Systems and Galaxies ii. Major Galaxy Types i. Spiral Galaxies: appear to have a bulge in the middle and arms that spiral out 1. The arms contain gas, dust, and many bright stars

II. Star Systems and Galaxies ii. Elliptical Galaxies: look like a round, flattened ball 1. Contain billions of stars but have very little gas and dust between them

II. Star Systems and Galaxies iii. Irregular Galaxies: do not have a shape i. Contains many young bright stars and lots of gas and dust between them

II. Star Systems and Galaxies iv. Quasars: Have extremely bright objects that look like stars 1. Are also called Quasi-stellar 2. Active galaxies with huge black holes at their centers

Warm up #1 Re-write the question and write your answer in complete sentences 1.What are the four different types of galaxies? 2.Describe a Quasar. 3.How do planets stay in orbit? What are the two factors that work together?

III. Gravity and Motion a.Gravity attracts all objects toward each other b.Newton’s Law of Universal Gravitation states that every object in the universe attracts every other object i. The strength of the gravitational force between two objects depends on two factors: the mass of the objects and the distance between them

III. Gravity and Motion ii. Mass: the amount of matter in a given object 1. Mass does not change iii. Weight: the measure of gravity on a given object 1. Weight changes when in different gravities

III. Gravity and Motion iv. Gravity will rapidly decrease as object move further away from one another v. Example of Gravity, Mass, Distance Draw arrows showing the force of gravity in the second and third pictures (the longer the arrow the greater the force)

III. Gravity and Motion c. Gravity is what helps keep objects in orbit d. Working against gravity is inertia i. Inertia falls under the first law of motion 1. An object in motion will stay in motion unless acted on by an outside force ii. Example e. Graph how force of gravity changes over distance

IV. Characteristics of Stars a.Classification of stars goes by: color, temperature, size, composition, and brightness b.Color and Temperature i. The color a star looks says something about its temperature ii. The coolest stars with a surface temperature of 3,200 C appear red

IV. Characteristics of Stars iii. Stars that appear yellow, like our sun have a surface temperature of about 5,500 C iv. Bluish-white stars are about 20,000 C

IV. Characteristics of Stars c. Size i. Many stars are about the same size as the sun ii. There are a large number that are actually much bigger than the sun iii. Very large stars are called giant stars or supergiant stars iv. Most stars are smaller than the sun v. White-dwarf stars are about the size of earth vi. There is also a star called a Neutron Star, which is only about 20 km in diameter (about 12 miles)