Warm-Up  Have you ever heard the statement, “We are all stardust”? Do you believe this to be true? How could this statement be true?  Crosby, Stills, Nash and Young even wrote a song about it…. 

Learning Target: Communicate scientific ideas about the way stars, over their life cycle, produce elements. Success Criteria:  Describe the properties of stars including mass, magnitude (luminosity) and color.  Identify the relationships between the lifecycle of the stars, the production of elements, and the conservation of protons and neutrons in stars.  Identify that atoms are not conserved in nuclear fusion, but the total number of protons plus neutrons is conserved.  Describe that helium and other light nuclei (up to lithium) were formed from high- energy collision starting from protons and neutrons in the early universe before any stars existed.  Describe that more massive elements (up to iron) are produced in the cores of stars by a chain of processes of nuclear fusion, which also releases energy.  Describe how supernova explosions of massive stars are the mechanism by which elements more massive than iron are produced.  Describe that there is a correlation between a star’s mass and stage of development and the types of elements it can create during its lifetime.  Describe how electromagnetic emission and absorption spectra are used to determine a star’s composition, motion and distance to Earth.

Vocabulary  Supernova : an astronomical event that occurs during the last stellar evolutionary stages of a massive star's life, whose dramatic and catastrophic destruction is marked by one final titanic explosion. For a short time, this causes the sudden appearance of a 'new' bright star, before slowly fading from sight over several weeks or months. massive star  Nuclear fusion : a nuclear reaction in which two or more atomic nuclei come close enough to react and form one or more different atomic nuclei and subatomic particles (neutrons and/or protons)nuclear reactionatomic nuclei  Red Giant: type of star near the end of a star’s life; temperature near the stars core rises and this causes the size of the star to expand

Properties of Stars  Describe the properties of stars including mass, magnitude (luminosity) and color.  What makes up a star’s mass?  Mostly hydrogen!!!  More hydrogen = more energy  Magnitude is the same thing as luminosity  Luminosity is the amount of energy it radiates per second  In other words, how bright or dim it is  Color tells us about the temperature of the star  Red= cooler  Blue= hotter

Determining a Star’s composition, motion and distance to Earth  Activity: Classifying Stars!!

Lifecycle of Stars  Identify the relationships between the lifecycle of the stars, the production of elements, and the conservation of protons and neutrons in stars.  Describe that there is a correlation between a star’s mass and stage of development and the types of elements it can create during its lifetime  A Star’s mass determines its life story!  High mass stars live for shorter amounts of time, they eventually make iron and end as supernovas.  Low mass stars live for longer amounts of time, they never get hot enough to make iron and thus only fuse up to carbon nuclei, and end as white dwarfs.

Life Cycles of Smaller Stars  © Sea & Sky

Life Cycles of Massive Stars  © Sea & Sky

Activity: Lifecycle of a Star

Making Elements  Identify the relationships between the lifecycle of the stars, the production of elements, and the conservation of protons and neutrons in stars.  Identify that atoms are not conserved in nuclear fusion, but the total number of protons plus neutrons is conserved.  Describe that helium and other light nuclei (up to lithium) were formed from high-energy collision starting from protons and neutrons in the early universe before any stars existed.  Describe that more massive elements (up to iron) are produced in the cores of stars by a chain of processes of nuclear fusion, which also releases energy.  Describe how supernova explosions of massive stars are the mechanism by which elements more massive than iron are produced.

How Do Stars Make Elements? Sun generates energy in its core by “cooking” hydrogen to form helium. This is called nucleosynthesis.

Nucleosynthesis Protons and Neutrons are conserved. They fuse to form new elements. Requires and releases immense heat

Nuclear Fusion The “cooking” of elements is called nuclear fusion During nuclear fusion, two or more atoms of one element combine to form one atom of a different element

Conservation of Protons and Neutrons Protons and Neutrons can not be created nor destroyed It is an addition problem!

Time to Practice!!!

Literacy  The Elements: Forged in Stars. (n.d.). Retrieved August 24, 2016, from Pre-Reading Activity: Read Background Essay and answer the following questions. 1. Create an illustration of an ordinary atom of Hydrogen as well as its isotope Deuterium. 1. What do you think the isotope of Hydrogen called Tritium looks like? 2. Create a drawing to illustrate the three steps in the nuclear fusion or nucleosynthesis process that creates the energy of the sun. 3. What is Helium capturing when it creates new elements?

Elements in the Universe Hydrogen and some helium was made at the beginning of the Universe (Big Bang). All other elements were made inside of stars, and then spewed out into space by the supernova explosions! Low mass stars up to carbon High mass stars up to iron What about elements with atoms heavier than iron? Such as Uranium, Gold, and so on?  The heavy atoms are made during the supernova explosion itself!  There is so much energy during the explosion that iron atoms can be forced together to form larger atoms.

Interior of a Massive Star Just before a supernova, the inside of the star has shells of various elements.

Supernova Remnants X-ray picture of the “Cas-A” supernova remnant. The elements in this gas will eventually be dispersed into space, maybe to form new stars, planets and people!

Describe how electromagnetic emission and absorption spectra are used to determine a star’s composition, motion and distance to Earth  Every substance gives off light when it gets hot enough.  Each element gives off its own special color.  We use spectra to determine which elements make up stars.  Motion and distance is determined by the amount of red shift.  Red shift = moving away  The farther the star the greater the red shift (Hubble’s Law)