"Twinkle, twinkle little star,     How I wonder what you are.     Up above the world so high,     Like a diamond in the sky..."

The second line of this song could be changed by children singing it today.  We know what stars are!  We can determine their sizes and distance from Earth, as well as their temperatures, compositions, and ages.  The tools of astronomy allow us to reveal their pasts and predict their futures.

Stars shine because they are nuclear power plants.  They turn the most abundant material in the Universe- hydrogen- into energy, helium and the other elements.  This process consumes stars and at the same time provides the energy and materials to remake them.  At the cosmic level, recycling of the old produces new stars and planets and shapes and reshapes the galaxies around black holes and quasars.
 
 
 
 

Investigation One: Cosmic Recycling
Our Sun is not a first generation star, which means that it is the product of many rounds of cosmic recycling.  Find the connections between stars at different points in the process to discover how they are made, change, and remade over time.

Materials:
    * computer with internet access
    * Cosmic Recycling Worksheet
    * Cosmic Recycling Worksheet Key

Procedure:
1.  Print the Cosmic Recycling Activity Sheet for each student.
2.  Go to Cosmic Recycling.  Use the resources there and under Hot Links to learn about each stage of the stellar
     recycling process.
3.  Integrate and synthesize information to describe the connection between each group of items on the activity sheet.
 

Questions:
* What is the connection between star size, mass and color?
* How does stellar size affect the cosmic recycling process?
* What does the presence of many different elements on Earth tell us about the formation of the planet?

Extensions:
    *  Write a script for one of the cosmic recycling movies:
     From Beginning to End
     Red to Black Dwarf
     Red Dwarf
     Trip to a Globular Cluster

    *  Investigate the formation of the elements.

Investigation Two:  The Star Power Card Game
A star's power is directly related to its mass.  The greater its mass, the more gravitational pull it can exert to accumulate and compact material.  The more fuel it has, the denser and hotter its core becomes.  The higher the temperature and pressure are, the faster the nuclear fusion reactions occur.  The greater the speed at which hydrogen atoms are fused into helium, the more energy the star has to fuse hydrogen and helium atoms into carbon and other heavier elements.  The brighter it shines, the faster it depletes its fuel and moves through the cosmic recycling process.  The higher the star power, the more points are earned in a game with the Cosmic Recycling Deck!

Note: Mass is expressed in solar mass multiples, which means it is compared to the mass of our Sun (a solar mass of .5 is half the Sun's mass and a solar mass of 2 is twice the Sun's mass).
    * Cosmic Recycling "StarPower" Playing Cards PDFs 1-2-3-4-5-6-7-key
 
 

Procedure:
Use the Cosmic Recycling Playing Cards to play standard card games:
1. War - use the star power points to take pairs
2. Rummy - collect three of a kind or cosmic recycling sequences
3.Concentration - match pairs
4. Go Fish - collect the most categories
5. Solitaire - create power point or cosmic recycling sequences

Questions:
* Why are the masses of yellow dwarfs and red giants the same?
* Why do black holes have more star power points than black dwarfs?
* Why do supernovas have less power points than blue and white giants?
* Why doesn't nuclear fusion occur in the interstellar material?
 

Extensions:
    * Explain the sequence of points from 1 to 15.
    * Arrange the cards to illustrate the cosmic recycling process.
    * Add new fact cards to the deck.

Investigation Three: Survey the stars
The twinkling white lights in the night sky include a variety of objects and star types.   Scattered across the heavens are distant galaxies and star clusters; blue and white giants; red giants and supergiants; and red, yellow, white and brown dwarfs.  Use the interactive Sky Images link to conduct a survey of the stars and search for the rare neutron stars, black holes and quasars.  Keep records of observations to find out which types of stars are the most common.

Materials:
    *  computer with internet access
    *  Star Survey Record Sheet

Procedure:
1. Print the Star Survey Record Sheet for each student.
2. Go to the Sky Image .  Explain that each point of light can be observed by clicking on it and finding the object's number and type.
3. Develop a plan to sample the stars or conduct a star by star survey.
4. Assemble data from student observations and discuss.

Questions:
* What types of stars are the most common?
* Why aren't the brightest points of light always the biggest and hottest stars?
* Why are supernova explosions rare?
* What does the number of yellow dwarfs reveal about the possiblity of other solar systems?

Extensions:
    * Find out what astronomers learn from the spectra of stars.
    * Find out how astronomers are using the Sloan Digital Sky Survey.