LESSON 5 THE LIVES OF STARS Stars are

LESSON 5 - THE LIVES OF STARS • Stars are born in nebulas • A nebula is a large cloud of gas and dust spread out in an immense volume. • A protostar is the first stage of a star’s life. • “proto” means first • Nuclear fusion is what begins a protostar

LIFETIME OF STARS • The greater the mass of a star, the shorter it lives. • Just like large car burns fuel faster than a small one, more massive stars burn out faster than less massive ones • Our sun will live for about 10 billion years. Since it has been burning for around 4. 6 billion, it is around halfway through its lifespan (it’s middle-aged!) • Supergiant stars may only live for about 10 million years, which is actually a very small

A STAR’S DEATH • After a star runs out of fuel, it becomes a white dwarf, a neutron star or a black whole. • The way a star dies depends on how massive it was to start with. • Low mass and medium mass stars take a long time to run out of fuel: they become white dwarfs. • After a few billion years they will stop glowing and become black dwarfs. • High-mass stars burn quickly and can explode suddenly! • The explosions of these stars are called supernovas. They are brighter than millions of our suns. The material from the explosion expands out into space. • Supernova explosions provide the incredible amounts of energy to create some of the heaviest elements in the universe.

AFTER A SUPERNOVA- NEUTRON STARS • Sometimes the material leftover from a supernova explosion creates a neutron star. • They are even smaller and denser than white dwarfs. They are only about the size of a city. • When neutron stars start to spin they are called pulsars. These spin extremely fast.

AFTER A SUPERNOVA- BLACK HOLES • The most massive stars may become black holes when they die. • A black holes an object with gravity so strong that nothing, not even light, can escape. • When the star explodes, more than 5 times the mass may be left. This energy and mass accretes and can form a black hole • Scientists can detect black holes by seeing X-rays being emitted from heated gas being sucked into them.

GRAB BOARD Write # 1 -8 A on. WHITE your white board -Without using your chapter pages try to label the sun image below AND A MARKER Word Bank • Corona • Prominance • Photosphere • Chromoshere • Radioactive zone • Sunspot • Convection zone • core

ANSWERS

LIFE CYCLE OF A LOW-MASS OR MEDIUM-MASS STAR (INCLUDING THE SUN)