STARS QUESTION • When you think of a star, what comes to mind? WHAT IS A STAR? • Star- a fixed luminous point in the night sky that is a large, remote incandescent body. • Stars are a big ball of gas. • It is held together by its own gravity. • They are made mostly of hydrogen and helium. • The closest star to Earth is the Sun. HOW ARE STARS MADE? • Stars are born in nebulas, which are like star nurseries. • In a nebula, gravity forces gas together. • As the gas comes together, it heats up and the hydrogen in the gas starts to speed up. • Eventually, the gases form a dense, hot core. • The core is middle of the star and it provides the fuel for the star’s entire life. ARE ALL STARS THE SAME? • Just like people, stars come in different sizes and colors. • The main types of stars are: • Dwarf • Main Sequence • Giant • Super Giant • Dwarf Star- a very small stars with small mass. • The most common type of star in the DWARF STARS universe. • They burn very slowly • They live for a very long time. • Some can life for trillions of years before they run out of fuel. • They also don’t shine brightly. • Example- Proxima Centauri • Two Types: • White Dwarf • One of the hottest stars in the universe. • Red Dwarf • The coldest stars in the universe. MAIN SEQUENCE STARS • Also known as medium stars. • Our sun is a main sequence star. • They are usually yellow in color. • They have a medium temperature. • These stars typically live for about 10 billion years. • When these stars start to die, they get larger and then rapidly shrink. • When this happens to the Sun in a few billion years, the Sun will get so large that it will engulf the Earth. GIANT STARS • These are the stars that are close to the end of their life. • They are typically red in color and are cooler in temperature. • When a main sequence star gets old, it starts to run out of hydrogen fuel. • The core begins to compress and the core begins to burn a helium fuel. • The helium fuel causes the star to enlarge and become a giant. • Many of the stars we see in the sky at night are giant start. • Example- Betelgeuse BLUE GIANT STARS • These are very rare giant stars. • They are one of the hottest stars, and they shine very brightly. • Even though they are rare, they make up many of the stars we see at night because they are so bright. • When these stars die, they expand and explode. • This explosion is called a supernova. SUPER GIANT STARS • A super giant star is the exact same thing as a giant star, but much larger. • Largest known type of star. • Example- Rigel • When these stars die, they often turn into black holes. • As the star explodes in a supernova, most of the star’s pieces are blasted away. • The pieces that remain, begin to fall in the middle and compress forming a black hole. LET’S COMPARE SIZES https://www.youtube.com/watch?v=HEheh1BH34Q https://www.youtube.com/watch?v=wHiHFXtE0js .