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Bellwork. 1. Define AU 2. What do we call the 3 Laws of Planetary Motion?. Chapter 3 Section 4 Planetary Motion Review. Visual Concepts online Ch3Sec4 Planetary Motion worksheet. Create a Chart.
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Bellwork • 1. Define AU • 2. What do we call the 3 Laws of Planetary Motion?
Chapter 3 Section 4 Planetary Motion Review • Visual Concepts online • Ch3Sec4 Planetary Motion worksheet
Create a Chart In your note book create a KWL chart and write what you know about how stars are formed. Also summarize what you know about the life cycle of a star? Next fill in the W.
Objectives • Describe the different types of stars • Describe how color indicates the temperature of a star • Describe the quantities that are plotted in the H-R diagram
Chapter 2: Section 2&3 How is a star born? • begins as a ball of gas and dust • Gravity causes the debris to form a sphere • As it gets denser it becomes hotter creating the right setting for nuclear fusion to occur. • Hydrogen begins to change into Helium
Life Cycle of a Star: - Stars are classified by their size, brightness, color, temperature, spectrum and age. - Stars progress through the same life cycle, but the larger, hotter, and brighter stars progress much faster.
Life cycle sequence • Stars begin as a large cloud of gas and dust called a nebula • Once stars are formed they enter the main sequence stage. In this stage they continuously generate energy in the core through nuclear fusion. • Size, structure and composition change very little during this stage. Eskimo Nebula
A Tool for Studying Stars • The H-R diagram is a graph that shows the relationship between a star’s surface temperature and its absolute magnitude.
Life sequence continued… • The third stage occurs when a star becomes a Red Giantor aRed Super Giant. • This occurs when a star has used all of it’s hydrogen and begins to expand and cool. This causes the core to shrink, which then causes the rest of the sun’s atmosphere to expand. • Red Giants can about ten times larger than the sun. • Super giants are at least 100 times larger than the sun.
Important terms • Nebula • Main sequence • Red/Super Giant • Ball of dust and gas- beginning of a star. • Constant Energy generated through nuclear fusion. The longest stage of a star. • A star that is expanding and cooling; hydrogen is no longer generating energy. 10x larger /100x larger than sun.
Life sequence continued… • The final stage of a star’s life cycle is a white dwarf. • A white dwarf is an old star’s leftover center that is no longer generating energy (no hydrogen left) • White dwarfs can shine for billions of years before cooling completely
Life cycle of a Star: Death of a Star • Stars usually lose material slowly unless they are blue stars. • Blue stars lose their energy fast and can sometimes explode in a bright flash called a Supernova, which is actually the collapse of the star.
Super Novas can become: Neutron stars- stars that have collapsed under gravity Pulsar stars – -spinning neutron stars that have jets of particles moving almost at the speed of light streaming out above their magnetic poles. -The beams of light sweep around as the pulsar rotates, just as the spotlight in a lighthouse does. -Like a ship in the ocean that sees only regular flashes of light, we see pulsars turn on and off as the beam sweeps over the Earth. -This along with the light being refracted by Earth’s atmosphere creates a stars “Twinkling” appearance
Interesting trivia • Pulsars spin fast for the same reason ice skaters pull in their arms to spin. This is conservation of angular momentum. Pulsars are formed with a certain amount of angular momentum. As gravity causes them to shrink (and thus have a smaller radius) they must spin faster in order to conserve angular momentum. http://imagine.gsfc.nasa.gov/docs/science/try_l1/pulsar.html
Black Holes • Leftover supernovas that are so massive they collapse into an object called a black hole • Light can not escape a black holes gravity because it is so massive • They are only detected through x-rays that can determine a black hole through materials from stars filtering through it
Myths vs. realities of black holes Hubble Space Telescope
Important terms • Final stage, no hydrogen left. Can shine for billions of yrs. • Blue stars that explode in a bright flash. • Stars that collapse from the gravity-pulsars spin. • Leftover supernovas that collapse into themselves forming gravity so massive that no light can escape. White Dwarf Supernova Neutron/Pulsar star Black hole
This artist's concept depicts a super massive black hole at the center of a galaxy. NASA's Galaxy Evolution Explorer found evidence that black holes -- once they grow to a critical size -- stifle the formation of new stars in elliptical galaxies. Black holes are thought to do this by heating up and blasting away the gas that fuels star formation. • The blue color here represents radiation pouring out from material very close to the black hole. The grayish structure surrounding the black hole, called a torus, is made up of gas and dust. Beyond the torus, only the old red-colored stars that make up the galaxy can be seen. There are no new stars in the galaxy. Image Credit: • NASA/JPL-Caltech
Color of Stars • What Is the Color of Hot? Although red and yellow may be thought of as “warm” colors and blue may be thought of as a “cool” color, scientists consider red and yellow to be cool colors and blue to be a warm color.
How Bright Is That Star? • Apparent MagnitudeThe brightness of a light or star is called apparent magnitude. How luminous the star is as it is viewed from Earth. • Absolute Magnitude Absolute magnitude is the actual brightness of a star. Measurement of stars luminosity when placed at the same distance, absolute magnitudes show differences in actual luminosities.
The H-R diagram is a graph that shows the relationship between a star’s surface temperature and its absolute magnitude.
Objectives • Describe the different types of stars • Describe how color indicates the temperature of a star • Describe the quantities that are plotted in the H-R diagram
