Yr+10+Universe





7.1 - Questions 1 to 11

Star Life Cycle Web Activity Go to []. Click on each of the links. READ all the information (as well as the animation links and interactive labs). Give detailed answers for the following questions. //Read the Introduction//
 * 1) Based on the diagram, how do all stars start?
 * 2) What are the main determining factors as to whether a star ends up as a black dwarf, neuron star or black hole?
 * 3) Using the human life cycle analogy, what star phase is the birth of a star and what is the usual end stage (death) of the star?
 * 4) Describe what the interstellar medium is. What are the three elements involved?

//Prostars- A star is born//
 * Play the animation that shows how a star begins to form from a nebula, and also play the equilibrium animation. Read the text on the page.**
 * 1) Define nebula and describe what equilibrium is for a star.
 * 2) What are the two main options for a prostar and what determines which pathway a prostar will take?

//Main Sequence//
 * Read the entire page. Click on __beginning of their life cycles__ interactive lab.**
 * 1) Which star has the longer life span, a larger one or a smaller one? Explain why.

//Equilibrium// Stars repeat a cycle of reaching equilibrium and then loosing it after burning out one fuel source, then condensing (shrinking) because of gravity, making the core more dense and hotter. The core gets so hot that now a new element can be used as a fuel source to burn and equilibrium is reached once again. Eventually the fuel sources run out and the star dies or explodes. The main fuel sources are hydrogen, helium and carbon. //Practice Quiz.// //Star Quiz (part 1)//
 * Read the webpage and the summary.**
 * 1) Nuclear fusion is the process of fusing (combining) two elements together under extremely high temperatures to form new, heavier elements. What are the three main fuels that a star can use for fusion reactions?
 * Work through the quiz.**
 * 1) Write down the answers to each of the quiz questions.
 * 1) Use the answers in the quiz to give a logical sequence (6 steps) describing what happens once the main sequence star runs out of hydrogen fuel, until the point where it reaches equilibrium again.

//After Main Sequence// //The end of a star// //The Hertzsprung-Russel (H-R) Diagram Introduction// A H-R diagram shows a wide array of stars plotted on a graph showing luminosity verses surface temperature (not core temperature). //Star life cycle web quiz// black hole, red giant, super nova, white dwarf, brown dwarf, prostar, black dwarf. - the final stage of most small to medium sized stars. - an intermediate phase of medium sized stars when carbon is the product of nuclear fusion - a stage reached only if the prostar never begins the fusion process. - a brilliant explosion leading into the formation of a neutron star or black hole. - the final stage of the most massive stars. - a cloud of dust and gas beginning to condense on itself because of gravity.
 * Read this page and do the star quiz (part 2)**
 * 1) As the outer shell of the star expands, the surface temperature of the star decreases (even though the core is getting hotter). Why does the surface temperature decrease?
 * Read the page and do the interactive lab.**
 * 1) What is the final outcome for a low mass star, a medium mass star and a massive mass star?
 * 2) Explain how a supernova can explain the formation of elements heavier than iron.
 * Read the page and do the interactive lab.**
 * 1) Which named star shown on the H-R diagram is a white dwarf and which is a super giant? Why are they given these names?
 * 2) Define luminosity.
 * 3) What is the relationship between the brightness of a star and the relative size of a star? Explain why.
 * This is to test your knowledge on the web activity.**
 * 1) Match the word with the definition.
 * 1) What happens initially to the core temperature and the gas pressure of a star when it runs out of hydrogen fuel for its fusion reactions?