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. K What do you know? W What do you want to know? L What did you learn?

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

How is a star born? Chapter 2: Section 2&3 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

The Birth 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 of a Star:

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.

The Hertzsprung Russell Diagram

HR Diagram: The abundance of main sequence stars

Life sequence continued… The third stage occurs when a star becomes a Red Giant or a Red 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 Ball of dust and gas- beginning of a star. 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.

Betelgeuse star

Betelgeuse is a red super giant

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

White Dwarfs

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.

Death of a Stars

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

Neutron Stars and Blackholes

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.

Stellar Spectrum

How Bright Is That Star? Apparent Magnitude The 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.

Brightness and Luminosity

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