Stars & Galaxies

1. Stars & Galaxies When sun goes home behind the trees, and locks her shutters tight--- Then stars come out with silver keys to open up the night. Norma Farber

2. Table of Contents • Units of Measurement • Galaxies • Life Cycle of a Star • Sun

3. Birth of a Star • Dust & gas particles collect to form a nebula • Temperatures begin to rise, at 10 million K the nebula begins to fuse together… • A main sequence star is created

4. Growth of a Star • Main sequence stars are fueled by hydrogen • They become a Giant or a Supergiant when all the fuel is gone • As the structure of the Giant star collapses it becomes a white dwarf • As the structure of a Supergiant collapses it becomes a supernova

5. Death of a Star • The white dwarf is the final stage of a Giant • The neutron star or a black hole is the final stage of a Supergiant WIYN Image

6. What Color Am I? • A star’s color is determined by how hot it is • The color will range from orange-red (cool) • To blue-white (hot)

7. What do you know? • What is the name given to a newly formed star? • What gas fuels a star? • The final stage of a Giant is called… • What determines a star’s color?

8. Works Cited • Bishop, David. Supernova Gallery. Latest Supernovae. February 11, 2003. Rochester Academy of Sciences. February 7, 2004. www.rochesterastronomy.org/snimages. • Kennedy, Dorothy and X.J. Kennedy. Talking Like the Rain. Boston: Little, Brown and Company, 1992. • Sharp, Nigel, et. al. Far Red/Near Infrared Image of the Dumbbell Nebula. NOAO Image Gallery. January 2, 2004. National Optical Astronomy Observatory. February 7, 2004. www.noao.edu/image_gallery/stars.html. • Barclay, Tom, et al. “Hertzsprung-Russell Diagrm,” SDSS Skyserver. Sloan Digital Sky Survey. February 28, 2004. Skyserver.fnal.gov/en/proj. • “EIT 304.” SOHO Exploring the Sun. February 28, 2004. Solar & Heliospheric Observatory. February 28, 2004. sohowww.nascom.nasa.gov/data/realtime/eit_304/512

9. Astronomical Units of Measurement • Taking measurements of space can be very difficult due to the vast spaces and distances. • Specific terms are used to quantify these special distances. • The brightness of stars are measured by absolute and apparent magnitude.

10. Magnitude • Stars may appear brighter because they are larger than other stars or because they are simply closer to earth. • A star’s absolute magnitude is the measure of how much light the star actually gives off. • A measure of how much light we receive on earth from any given star is its apparent magnitude.

11. Parsecs • A star’s distance from earth is measured in parsecs. • This is a measurement for a specific multiple of light-years (3.26). • A light-year is the distance that light travels in one year. Light can travel at 300,000 km/s. So one light-year is equivalent to 9.5 trillion km.

12. Parallax • The method for determining a star’s distance is to measure its parallax. • An objects parallax is its apparent shift in position when viewed from two different places or locations.

13. What do you Know? • Which magnitude measures the brightness of light received on earth? • How many light-years are equivalent to one parsec? • What method is used to measure the distance of stars?

14. Our Sun • Our sun is an average star, because its yellowish light is in the middle of the color spectrum. • Usually two stars will orbit around each other. This is called a binary system. Our sun is a unique star, because it orbits by itself.

15. Energy from the Sun • The sun’s energy is produced in its core by hydrogen gases fusing into helium. • The heat radiates out through the convection zone.

16. Layers of the Sun • The sun has layers similar to our earth. • They are as follows: • Core (innermost layer) • Radiation zone • Convection zone • Photosphere • Chromosphere (outermost layer)

17. Activity in the Chromosphere • Because the sun is a ball of boiling and churning gas, its surface is constantly changing.

18. Sunspots • Sunspots are cooler areas of the surface.

19. Prominences • Sometimes huge columns of gas arch across the sun’s surface. • These magnetic outbursts of energy are called prominences.

20. Solar Flares • Solar flares occur when the gases near a sunspot suddenly erupt and shoot outward at high speed. • Sometimes the ultra-violet light or x-rays from these high energy particles interfere with radio signals here on earth.

21. What do you Know? • How does the sun produce energy? • Which layer is at the surface? • What causes a sunspot? • Prominences are caused by what? • Solar flares occur near what other surface feature?

22. Galaxies • A galaxy is a large group of stars, gas, and dust held together by gravity. • There are three types of galaxies: • Spiral • Elliptical • Irregular

23. Spiral Galaxy • A spiral galaxy has a central grouping of stars with arms projecting out into space. • Our Milky Way galaxy is a spiral galaxy.

24. Elliptical Galaxy • Elliptical galaxies resemble a football. They are large three-dimensional ellipses or ovals.

25. Irregular Galaxy • An irregular galaxy does not have a specific shape. • This category is used to group any galaxy that does not fit into the spiral or elliptical category.

26. Milky Way Galaxy • The Milky Way is a spiral galaxy about 100,000 light years wide. • Our solar system rotates around the center region of this galaxy. • This galaxy contains about 200 billion stars. • The Milky Way is just one out of 30 galaxies that form a cluster. • This cluster is called the Local Group.

27. What do you Know? • The Milky Way Galaxy is what shape? • Which galaxy resembles a football? • What features do Irregular Galaxies have? • How many light-years across is the Milky Way Galaxy?