1. Elements from Stardust Chapter 3 Section 4

2. Where do Elements Come from? FWhere do you think rare elements come from? FIn order to answer this, scientists have formed some interesting hypotheses by studying the sun and other stars. FScientists have been looking in the inside of stars. FWhere do you think rare elements come from? FIn order to answer this, scientists have formed some interesting hypotheses by studying the sun and other stars. FScientists have been looking in the inside of stars.

3. Atomic Nuclei Collide FLike many other stars, the sun is made mostly of one element - hydrogen. FThis hydrogen exists at tremendously high pressures and hot temperatures. FHow hot is it? FThe temperature in the sun’s core is 15 million degrees Celsius. FLike many other stars, the sun is made mostly of one element - hydrogen. FThis hydrogen exists at tremendously high pressures and hot temperatures. FHow hot is it? FThe temperature in the sun’s core is 15 million degrees Celsius.

4. Plasma FAt such high pressures and hot temperatures found inside the sun and other stars, hydrogen does not exist as a solid, liquid or gas. FInstead it exists in a state called plasma. FIn the plasma state of matter, atoms are stripped of their electrons and the nuclei are packed close together. FRemember that atomic nuclei contain protons, which means that nuclei are positively charged. FNormally, positively charged nuclei repel each other. But inside stars where matter is in the plasma state, nuclei are close enough and moving fast enough to collide with each other. FAt such high pressures and hot temperatures found inside the sun and other stars, hydrogen does not exist as a solid, liquid or gas. FInstead it exists in a state called plasma. FIn the plasma state of matter, atoms are stripped of their electrons and the nuclei are packed close together. FRemember that atomic nuclei contain protons, which means that nuclei are positively charged. FNormally, positively charged nuclei repel each other. But inside stars where matter is in the plasma state, nuclei are close enough and moving fast enough to collide with each other.

5. Nuclear Fusion FWhen colliding nuclei have enough energy, they can join together in a process called nuclear fusion. FIn nuclear fusion, atomic nuclei combine to form a larger nucleus, releasing huge amounts of energy in the process. FInside stars, nuclear fusion combines smaller nuclei into larger nuclei, thus creating heavier elements. FFor this reason, you can think of stars as “element factories.” FWhen colliding nuclei have enough energy, they can join together in a process called nuclear fusion. FIn nuclear fusion, atomic nuclei combine to form a larger nucleus, releasing huge amounts of energy in the process. FInside stars, nuclear fusion combines smaller nuclei into larger nuclei, thus creating heavier elements. FFor this reason, you can think of stars as “element factories.”

6. Elements from the Sun FWhat are the steps of nuclear fusion in the sun and other stars? FA hydrogen nucleus always contains one proton. FHowever, different types of hydrogen contain 2 neutrons, 1 neutron, or 0 neutrons. FInside the sun, hydrogen nuclei undergo a nuclear fusion reaction that produces a helium nuclei. Notice that this requires the type of hydrogen nuclei that has neutrons. FThis type of hydrogen is rare on Earth but common inside of the sun. FLook on page 105 to see the illustration in Figure 25. FWhat are the steps of nuclear fusion in the sun and other stars? FA hydrogen nucleus always contains one proton. FHowever, different types of hydrogen contain 2 neutrons, 1 neutron, or 0 neutrons. FInside the sun, hydrogen nuclei undergo a nuclear fusion reaction that produces a helium nuclei. Notice that this requires the type of hydrogen nuclei that has neutrons. FThis type of hydrogen is rare on Earth but common inside of the sun. FLook on page 105 to see the illustration in Figure 25.

7. Hydrogen Nuclei form Helium Nuclei + + + + + + + + Hydrogen nuclei Helium nuclei Helium Hydrogen (with and without neutron) (one neutron each nucleus nucleus ++ + +

8. The Sun’s Source of Energy FAs two hydrogen nuclei fuse together, they release a great deal of energy. FIn fact, this reaction is the major source of the energy that the sun now produces. FIn other words, hydrogen is the fuel that powers the sun. FScientists estimate that the sun has enough hydrogen to last another 5 billion years and then it will eventually run out. FAs two hydrogen nuclei fuse together, they release a great deal of energy. FIn fact, this reaction is the major source of the energy that the sun now produces. FIn other words, hydrogen is the fuel that powers the sun. FScientists estimate that the sun has enough hydrogen to last another 5 billion years and then it will eventually run out.

9. How elements are produced FAs more and more helium builds up in the core, the sun’s temperature and volume change. FThese changes allow different nuclear reactions to occur. FOver time, two or more helium nuclei combine to form the nuclei of slightly heavier elements. FAs more and more helium builds up in the core, the sun’s temperature and volume change. FThese changes allow different nuclear reactions to occur. FOver time, two or more helium nuclei combine to form the nuclei of slightly heavier elements.

10. The Process FFirst, two helium nuclei combine, forming a beryllium nucleus. Then another helium nucleus can join with the beryllium nucleus, forming a carbon nucleus, And another helium nuclei joins the carbon nucleus, forming oxygen. FStars the size of the sun do not contain enough energy to produce heavier elements than oxygen. FFirst, two helium nuclei combine, forming a beryllium nucleus. Then another helium nucleus can join with the beryllium nucleus, forming a carbon nucleus, And another helium nuclei joins the carbon nucleus, forming oxygen. FStars the size of the sun do not contain enough energy to produce heavier elements than oxygen.

11. Elements from Larger Stars FAs they age, larger stars become even hotter than the sun. FThese stars have enough energy to produce heavier elements, such as magnesium and silicon. FIn more massive stars, fusion continues until the core is almost all iron. FAs they age, larger stars become even hotter than the sun. FThese stars have enough energy to produce heavier elements, such as magnesium and silicon. FIn more massive stars, fusion continues until the core is almost all iron.

12. Supernova FHow are elements heavier than iron produced? FIn the final hours of most massive stars, scientists have observed an event called a supernova. FA supernova is a tremendous explosion that breaks apart a massive star producing temperatures up to one billion degrees Celsius. FA supernova provides enough energy for the nuclear fusion reaction that creates the heaviest elements. FHow are elements heavier than iron produced? FIn the final hours of most massive stars, scientists have observed an event called a supernova. FA supernova is a tremendous explosion that breaks apart a massive star producing temperatures up to one billion degrees Celsius. FA supernova provides enough energy for the nuclear fusion reaction that creates the heaviest elements.

13. Where did the Matter of the Sun and Planets Come From? FMost astronomers agree that the matter in the sun and and the planets around it, including Earth, originally came from a gigantic supernova that occurred billions of years ago. FIf this is true, it means that everything around you was created in a star. FSo all matter on Earth is a form of stardust. FMost astronomers agree that the matter in the sun and and the planets around it, including Earth, originally came from a gigantic supernova that occurred billions of years ago. FIf this is true, it means that everything around you was created in a star. FSo all matter on Earth is a form of stardust.