Date post: | 01-Apr-2015 |
Category: |
Documents |
Upload: | brooklynn-masterson |
View: | 214 times |
Download: | 1 times |
Notes 30.3 Star Groups
• Std 2a: Know that the solar system is located in the outer edge of the disc-shaped Milky Way galaxy
• Std 2b: Know galaxies are made of billions of stars and comprise most of the visible mass of the universe
• Objective 1: Describe the characteristics that identify a constellation
• Objective 2: Describe the three main types of galaxies • Objective 3: Explain how a quasar differs from a
typical galaxy
• There are trillions of stars in the universe.
• Most stars seen from Earth are within 100 light-years from Earth
Star Groups
• Star groups that form patterns can be identified by using a star chart
• The sky has been divided into 88 regions
• Describes the locations of celestial objects
• Constellation - a group of stars organized in a recognizable pattern
Constellations
• The constellations are used to locate particular stars
• The stars in a constellation appear close together when viewed from Earth, but they are very far from each other
Dividing up the Sky
• Many names come from Latin
• Real animals Ursa Major (Great Bear) or imaginary animals Draco(Dragon)
• Ancient or Legendary heroes (Orion’s belt)
Naming Constellations
Objective 1: Describe the characteristics that identify a constellation
• How many regional division of the sky exist?– 88 Divisions
• What is group of stars organized into patterns?– Constellation
• What language was used to name many constellations?– Latin
• What are 2 other ways constellations are named?– Animals or legends/heroes
• When two or more stars are closely associated, they form multiple-star systems
• Binary Stars - pairs of stars that revolve around each other and held together by gravity
• Multiple-star systems sometimes have more than two stars
• Astronomers estimate that more than half of all observed stars are part of a multiple star system
Multiple-Star System
• Nebulas collapse to form groups of 100’s to 1,000’s of stars called clusters
• There are Global clusters and Open clusters
Star Clusters
• A large-scale group of stars, gas, and dust that is bound together by gravity is called a galaxy
• The Milky Way Galaxy (which we live), has a diameter of about 100,000 light years and more than 200 billion stars
• There are hundreds to billions of galaxies
Galaxies
• Scientists look at certain stars absolute and apparent magnitude to determine distance to the galaxy
• Galaxies are classified by shape
1. Spiral galaxies
2. Elliptical galaxies
3. Irregular galaxies
Distance to Galaxies
• They have a nucleus of bright stars and flattened arms that spiral around the nucleus
• Some have a straight bar of stars that run through the center these are called barred spiral galaxies
1) Spiral Galaxies
• They vary in shape from spherical to elongated
• They are extremely bright in the center and do not have spiral arms
2) Elliptical Galaxies
• They have no particular shape
• Have low total masses and rich in dust and gas
• Rarest type of galaxy
3) Irregular Galaxies
Objective 2: Describe the three main types of galaxies
• What is a large-scale group of stars, gas, and dust that is bound together by gravity?– galaxy
• What are the 3 types of galaxies?– Spiral, elliptical and irregular
• Which galaxy is very bright and does not have arms?– Elliptical
• Which galaxy is the rarest type?– Irregular
• A Spiral Galaxy in which the sun is one of hundreds of billions of stars
• the name comes from the cloudlike “milky” appearance
• it takes the sun about 225 million years to orbit around the galaxy
The Milky Way
• Quasar is a shortened term for quasi-stellar (“similar to star”) radio source– Bright, old and most distant objects in the universe
• They are related to galaxies not stars
• They are at the center of young galaxies, causing their centers to be very bright
• Associated with giant black holes in the center
Quasars
Objective 3: Explain how a quasar differs from a typical galaxy
• What is a quasar?– Quasi-stellar radio source
• Where are quasars found?– Young galaxies
• What are they related to?– Galaxies not stars!
• What is commonly associated with a quasar?– giant black hole