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Chapter 2 Stars, Galaxies, and the Universe Notes
Transcript of Chapter 2 Stars, Galaxies, and the Universe Notes
Chapter 2 Section 1
Are actually huge, hot, bright balls of gas that are trillions of kilometers away from Earth
2. Color of Stars
3. The color of the star depends on the temperature of the star.
3. Warmer stars are blue
3. Cooler stars are red and yellow
2. Composition of stars cont.
3. Making an ID
4. Emission lines are lines that are made when certain wavelengths of light, or colors, are given off by hot gases.
4. Emission lines are like fingerprints for the elements.
3. Trapping the Light-Cosmic Detective Work
4. Electrically charged elements have spectrums made of bright emission lines, whereas stars have spectrums made of dark emission lines
4. A star's atmosphere absorbs certain colors of light in the spectrum, which causes black lines to appear
2. Composition of Stars Cont.
3. Identifying Elements using Dark Lines
4. Since star's atmosphere absorbs colors of light instead of emitting them, the spectrum of a star is called an absorption spectrum.
4.Where the colors are absorbed in a star's spectrum black lines appear
4. The pattern of lines in a star's absorption spectrum shows some of the elements that are in teh star's atmosphere.
The Death of a Star
2. Composition of Stars
Stars are made of different elements in the form of gases
The inner layers of a star's are very dense and hot.
Elements in a star's atmosphere absorb some of the light that radiates from the star
Scientince see what stars are made of by the light they give off
3. The Color of Light
4.Spectrum-the band of color produced when white light passes through a prism
4. Continuous spectrum-shows all the colors
4. Astronomers use an instrument called a spectrograph to break a star's light into a spectrum.
4. Astronomers look at the spectrum to know what a stars composition and temperature
1. Classifying Stars
1. How Bright Is That Star
2. How bright a star appears as seen from Earth is called apparent Magnitude
2. How bright a star acutally is absolute magnitude
2. Differences in Temperature
3. Stars are classsified by how hot they are
3. The hottest stars are blue
2. Differences in Brightness
3. A star's magnitude refers to its brightness
3. Early astronomers called the brightest stars first-magnitude
3. Early astronomers called the dimmest stars sixth magnitude
3. Now we can see more stars with bigger and better telescopes. Instead of replacing the old system fo magnitudes we just added to it.
4. Positive numbers represent dimmer stars, and negative numbers represent brighter stars
1. Distance to the Stars
2. Astronomers use light years to measure the distances from Earth to the Stars
2. Light-year is the distance that light travels in one year.
2. A star's apparent shift in position is called parallax.
The Life Cycle of Stars
Chapter 2 Section 2
1. Different Types of Stars
2. All stars are classified by their size, mass, brightness, color, temperature, spectrum, and age.
2. Some types of stars are main-sequence, giants, supergiant, and white dwarf
3. Giants and Supergiants
4. Third stage of its life cycle
4. It expands and cools and uses up all the hydrogen the core starts to shrink
4. Atmosphere grows very large and cools to form a red giant or a red supergiant
3. White Dwarfs
4.. Final stage of a star's life cycle.
4.Has no hydrogen left and no longer generates energy..
4. Can shine for billions of years before they cool completely.
3. Main -Sequence Stars
4. This is the second and longest stage of its life Cycle
4. Energy is generated in the core of the star as hydrogen atoms fuse into helium atoms.
1. The Beginning and End of Starts
2. Stars are formed by the pulling gas and dust together
2. Stars are made of gas
2. During a Star's Life cycle, hydrogen changes to helium in a process called Nuclear Fusion
2. As stars get older, they lose some of their material
2. When a star dies, either gradually or in a big explosion, much of its material returns to Space
1. A tool for Studying Stars
2. H-R Diagram
3. Named after two astronomers, Ejnar Hertzprung and Henry Norris Russell
3. Is a graph that shows the relationship between a star's surface temperature and its absolute magnitude.
2. Reading the H-R Diagram
3. Temperature is on the bottom
3. Absolute magnitude or brightness is on the left side
3. Hot or blue stars are on the left and cool stars are on the right
3. Bright stars are at the top, dim on the bottom
3. The diagonal pattern on the H-R diagram is where most stars lie (Main sequence)
3. Stars move up and to the right after Main-Sequence to become giants or supergiants
3. After they are giants or supergiants they move down and to the left to become white dwarfs
1. When Stars Get Old
3. Massive stars use their hydrogen much faster
3. Massive stars generate more energy
3. Massive stars may explode at the end of their life called supernova
3. Supernova is a gigantic explosion which a massive star collapses and throws its outer layers into space
2. Neutron Stars and Pulsars
3. A star that has collapsed under gravity to the point at which all the star's particles are neutrons is called a neutron star.
3. If a neutron star is spinning, it is called a pulsar
2. Black Holes
3. a Black hole is an object that is so massive that light cannot escape its gravity.
3. Nearby stars gas or dust will spiral into the black hole giving off x rays that can be detected by astronomers.
Chapter 2 Section 3
Galaxies are a collection of stars, dust, and gas bound together by gravity.
1. Types galaxies
2. Edwin Hubble developed the way we classify galaxies
2. Spiral Galaxies
3. Spiral galaxies have a bulge at the center and spiral arms.
4. The spiral arms are made up of gas, dust, and new stars
3. The Milky Way is a Spiral Galaxy
4. We think this because of making observations of other galaxies
2. Elliptical Galaxies
3. These Galaxies are massive blobs of stars.
3. Have bright centers and very little dust and gas.
3. Contain mostly old stars
3. Large elliptical galaxies are called giant elliptical while smaller ones are called dwarf elliptical galaxies.
2. Irregular Galaxies
3. These galaxies have irregular shapes.
3. These galaxies are close companions of another galaxy.
3. Many of these galaxies may have their shape distorted by these neighboring galaxies
1. Contents of Galaxies
2. Galaxies contain billions of stars and some planetary systems.
2. Some of these stars form gas clounds and star clusters.
2. Gas Clouds
3. In space large clouds of gas and dust are called nebulas.
4. Nebulas are often found in spiral galaxies.
4. Some type of nebulas glow
4. Some types of nebulas absorb light and hide stars.
2. Star Clusters
3. Globular clusters are tight groups of old stars that look like a ball
4. Are located in a sperical halo that surrounds spiral galaxies.
4. Are also common near giant elliptical galaxies
3. Open clusters are groups of closely grouped stars that are usually located along the spiral disk of a galaxy
4. Newly formed open clusters have many bright blue stars
Types of Galaxies
1. Origin of Galaxies
3. Are starlike sources of light that are extremely far away.
3. Are among the most powerful energy sources in the universe
3. May be caused by massive black holes in the core of galaxies
Quasars may be caused by massive black holes
Formation of the Universe
Chapter 2 Section 4
The Study of the origin, structure, and the future of the universe is called Cosmology.
1. Universal Expansion
2. To understand how the universe formed, scientists study the movement of galaxies.
2. Most Galaxies are moving apart.
2. The universe is expanding
1. The Big Bang Theory
2. The Big Bang Theory
3. The universe began with a tremendous explosion is called the Big Bang Theory.
3. The universe began 13.7 billon years ago compressed under extreme pressure, temperature, and density in a very small spot
2. Cosmic Background Radiation
3. Cosmic background radiation is left over from the big bang.
1. Structure of the Universe
2. The universe contains a variety of objects
3. Objects in the universe are part of an overall pattern
3. The universe has a structure that is loosely repeated over and over
3. Every objects is part of a larger system
4. From smallest to largest
cluster of galaxies