Presented by Kesler Science Life Cycle of a Star Created by Kesler Science – More 5E lessons at KeslerScience.com Presented by Kesler Science

Essential Questions: What is the life cycle of a star? How does the mass of a star predict the sequence of events in the life cycle of a star?

Life Cycle of a Star Vocabulary The sequence of changes that occur in a star as it ages. Infant Youth Middle Age Old Age Death This is a great time to talk about what a cycle is. Ask students to name all the cycles they know or have studied. The human life cycle is good for comparing to a star’s life cycle. © KeslerScience.com

This can be used to help students realize that stars progress through a life cycle. Make sure they understand that star life is in millions/billions of years. © KeslerScience.com

Quick Action – INB Templates Life Cycle of a Star Cut out the Life Cycle of a Star template. Glue it into your journal. Have the students fill in the names of each phase as you discuss the Vocabulary. © KeslerScience.com

A thinly spread area of gas and dust The gas is mostly hydrogen (H2) Life Cycle of a Star Vocabulary Where do stars come from? Interstellar medium A thinly spread area of gas and dust The gas is mostly hydrogen (H2) The dust is mostly carbon (C) and silicon (Si)  You might want to talk about the Big Bang here to help students understand where the gas and dust come from. © KeslerScience.com

Life Cycle of a Star Vocabulary Nebula Interstellar medium begins to collect into big clouds. The birthplace of stars, as stars are made up of gas and dust. “Star Nursery” At this time talk about gravity and how it starts to pull the gas and dust together. Every dust particle has a gravitational attraction to another dust particle. © KeslerScience.com

Protostar Life Cycle of a Star Vocabulary Inside the nebula are regions of greater and less gravity causing the gas and dust to pull together. As more atoms gather, their gravitational attraction increases. Not a very stable phase because many reactions are occurring within the protostar. Also talk about how these particles begin to heat up as they collide with each other. Help the students to understand this is not a star yet, just the beginning reactions that lead up to stars. How does this relate to a human life cycle? © KeslerScience.com

Equilibrium Life Cycle of a Star Vocabulary A battle between gravity and gas pressure Reactions within life cycle phases where gravity and gas pressure are constantly changing. Equilibrium is reached when both are equal. This is about the reactions taking place in the protostars. Equilibrium – How it Works Gravity pulls gas and dust inward The core temperature increases as gas atoms collide. Density of core increases as more atoms are pulled into the core. Gas pressure increases as more atoms collide. The protostar’s gas pressure resists the collapse (gravity) of the nebula The protostar reaches equilibrium when - gas pressure = gravity © KeslerScience.com

Hydrogen (H2) begins fusing into helium (He). Life Cycle of a Star Vocabulary A Star is Born – when a critical temperature in the core of the protostar is reached and nuclear fusion begins. Hydrogen (H2) begins fusing into helium (He). © KeslerScience.com

Star Life Cycle of a Star Vocabulary An extremely hot ball of gas, with hydrogen (H2) fusing into helium(He)at its core. Spend most of their lives fusing hydrogen When the hydrogen is used up, stars fuse helium to carbon They are always trying to achieve equilibrium © KeslerScience.com

Main Sequence Life Cycle of a Star Vocabulary Stars live out most of their lives in this phase. Stars have achieved nuclear fusion. Stars stays at equilibrium. Stars radiate (shine) energy into space. Stars in Main Sequence are constantly fighting to stay at equilibrium. © KeslerScience.com

Life Cycle of a Star Vocabulary Low Mass Stars in Main Sequence The mass of a star determines what happens to it after living most of its life in Main Sequence. © KeslerScience.com

Life Cycle of a Star Vocabulary Low mass stars – Half as massive as the Sun Can live 80 to 100 billion years in Main Sequence. Example - Red Dwarf Our Sun – A medium sized, low mass star Spends about 10 billion years in Main Sequence. A Main Sequence star for about 4.57 billion years. © KeslerScience.com

Red Giant Life Cycle of a Star Vocabulary Phase after Main Sequence Low and high mass Main Sequence stars progress to Red Giants. Outer gas layers of the star expand As the star uses all its fuel its core shrinks. Red in color High luminosity You might want to add information about the sun changing into a red Giant here. © KeslerScience.com

Planetary nebula Life Cycle of a Star Vocabulary Occurs at the end of a low mass Red Giant’s life. The outer layers of the star are expelled. The core is very hot and luminous. The outer shell appears as bright colored gas clouds.   © KeslerScience.com

White Dwarf Life Cycle of a Star Vocabulary Forms when a low mass star runs out of fuel. The core of a planetary nebula Final stage in the cycle for low mass stars Incredibly dense Gravity is 350,000 times that of gravity on Earth. Will change colors as it cools Talk about a gas flame so students get the concept of heating/cooling changing the color of the flame. Blue flames very hot. Yellow/orange flames cooler. © KeslerScience.com

Black Dwarf Life Cycle of a Star Vocabulary End product of a White Dwarf The last stage of stellar evolution for low mass stars No longer emits heat or light No longer a star © KeslerScience.com

Life Cycle of a Star Vocabulary Talk about how the sun is a medium size low mass star in Main Sequence and will follow the cycle of low mass stars through the life cycle. © KeslerScience.com

Quick Action – Life Cycle of a Star ______mass _____ mass Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence. © KeslerScience.com

Quick Action – Life Cycle of a Star Low Mass High Mass Main Sequence SUN Red Giant Star-Forming Nebula Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence. Planetary Nebula White Dwarf © KeslerScience.com

Life Cycle of a Star Vocabulary © KeslerScience.com

Life Cycle of a Star Vocabulary High Mass Main Sequence The mass of a star determines what happens to it after living most of its life in Main Sequence. © KeslerScience.com

Life Cycle of a Star Vocabulary High Mass stars - 10 times as massive as our Sun Remains in Main Sequence for about 20 million years. © KeslerScience.com

Life Cycle of a Star Vocabulary Red Super Giants The same thing as a giant star only much bigger. As a star gets older it begins to run out of fuel and expand. Here you could refer the back to the slide on Red Giants. © KeslerScience.com

Supernova Life Cycle of a Star Vocabulary Last stage of a massive star’s life Occurs as the star runs out of nuclear fuel, some of its mass flows into its core. Core becomes so heavy that it cannot withstand its own gravitational force. The core collapses and results in a giant explosion. © KeslerScience.com

Neutron Star Life Cycle of a Star Vocabulary The core left behind in a supernova Very dense - 1Tsp. = 1billion tons Gravity is 2 billion times that of the gravity on Earth. Gravity presses the material in on itself so tightly that protons and electrons combine to make neutrons, yielding the name "neutron star”. © KeslerScience.com

Life Cycle of a Star Vocabulary Black Hole Forms when very massive stars collapse at the end of their life cycle A large area in space with a very strong gravitational pull Nothing can escape, even light. © KeslerScience.com

Quick Action – Life Cycle of a Star Low Mass High Mass Main Sequence Massive Star SUN Red Super Giant Red Giant Star-Forming Nebula Have the students Trace the life cycle of the Sun on this diagram. They should realize it is the left side of the diagram. Have them label Sun under Main Sequence. Neutron Star Supernova Planetary Nebula White Dwarf Black Hole © KeslerScience.com

Quick Action – Life Cycle of a Star Journal Activity In your INB write a passage that compares the human life cycle to the life cycle of a star. Provide as much detail as possible. This is a great exercise to get students writing and reflecting on their knowledge. Allow them to use their resources for better results © KeslerScience.com

Check for Understanding __________ ___________ Can you… Describe why a star goes through a cycle? Predict what stages a low mass star will pass through in its lifetime? Label a blank Life Cycle of a Star diagram? Clear up any confusion and answer questions. © KeslerScience.com