Access Prior Knowledge Lesson 2: What is a star? Opening Activity Open Science textbook to page 518. Open Science folder to review vocabulary words and outline for the chapter. Open Science journal and answer the following question: 1. How is reusing and recycling beneficial for our planet? Review Content Cards and Q-Cards in bin, sharing with partners quizzing each other quietly. Log in to clickers using student ID number. Be ready to review home learning when timer goes off. Don't forget to write your home learning in your agenda page 161A.

Do you agree with the statement? The Sun is the largest of all stars YES NO

Do you agree with the statement? Stars that appear the brightest are also the closest. YES NO

Do you agree with the statement? Stars that are the hottest are white or blue-white. YES NO

Do you agree with the statement? Stars go through a long life cycle. YES NO

How the Sun Stacks Up as a Star The Sun is a star because all stars are very large balls of hot gases that give off electromagnetic radiation. The Sun gives off huge amounts of heat and light energy, due to very high heat and pressure that push hydrogen atoms together, creating helium. Huge amounts of energy are let go as this happens, making the Sun shine and we can only see this star during the day because its light prevents other stars from being seen.

Brightness, Color and Temperature of Stars The Sun is the closest star to Earth and the brightest and the brightest stars give off the most energy. -If the Sun is a gumball machine, the Earth is one gumball. How bright a star looks depends on the star’s size, temperature, and distance from Earth. -Sirius is larger, hotter, and brighter than the Sun, but it is the ninth closest star to Earth. Red stars are the coolest, orange and yellow stars are hotter and the hottest stars are white or blue-white, like Sirius. -Sirius does not look brighter than the Sun because it is much farther from us than the Sun. Distance is measured in light-years which is the distance light travels in one year, which is over 9 trillion kilometers. -Scientist measure the distance between stars and Earth in light-years because distances in space are huge compared to distances on Earth.

The Explosive Sun The Sun’s innermost layer is called the photosphere, which gives off the light we see. The layer above the photosphere is the chromosphere, and the outer layer is called the corona. Sunspots are dark spots that are part of the photosphere and are cooler than the rest of the photosphere and travels across the Sun indicating that the Sun rotates slower at its poles than it does at its equator.

Solar Eruptions Ribbons of gas called prominence leap out of the chromosphere that can also erupt like a volcano. This is a solar flare which can last for minutes or hours.

The Life of Stars New stars form in a nebula which is a cloud of dust and gas pulled together by gravity. -The temperature rises, hydrogen changes into helium, and the particles release energy; the particles become a star. A star can use up all of its hydrogen and helium and die. -The center of the star may shrink and cool, and then it becomes a white dwarf star. The star will take millions of years to become cold, and then it becomes a black dwarf star. -A very large star can run out of helium, and then it shrinks in on itself. When the star stops shrinking it causes a great explosion called a supernova. -A star can also die when the core of a large star shrinks in on itself until it becomes a black hole, which nothing can escape getting sucked into a black hole – not even light.

MatchQuest

TextQuest 1. Where are sunspots located and why are they dark? 2. How do new stars form? 3. Why is the sun so much brighter than any other star in our galaxy? 4. How is it possible that the sun is the only star we see during the day? 5. How does the color of a star relate to its temperature? Don't forget to write your home learning in your agenda page 161A.