What is a supernova? They Outshine Their Entire Galaxy. By NASA, adapted by Newsela staff on Word Count 675 Level 840L

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1 What is a supernova? By NASA, adapted by Newsela staff on Word Count 675 Level 840L TOP: A vivid view of a supernova remnant captured by NASA's Spitzer and Chandra space observatories and the Calar Alto observatory in Spain. Photo: MPIA/NASA/Calar Alto Observatory. BOTTOM: NASA's Hubble Telescope captured an image of Eta Carinae, one of the closest stars to Earth that is likely to explode in a supernova in the "relatively near future." In astronomical timescales, that "near future" could still be a million years away. Photo: ESA/NASA NASA.gov. When a star explodes, it is called a supernova. It is the largest explosion that happens in space. Supernovas are among the most powerful and amazing events in the universe. Most of the changes that take place in the universe happen very, very slowly. For example, it took millions of years for our solar system to form. It took another 4.5 billion years before one of its planets had intelligent life. A supernova, though, happens in only about 15 seconds. They Outshine Their Entire Galaxy A galaxy is a system of millions or billions of stars. Our solar system is in the Milky Way galaxy. From Earth, it is hard to see supernovas in the Milky Way galaxy. That's because the galaxy is filled with bits of dust that block our view. This article is available at 5 reading levels at 1

2 We can see supernovas in other galaxies, though. Astronomers are scientists who study planets and space. These experts believe that in galaxies like ours, about two or three supernovas happen every 100 years. Astronomers are usually able to observe a few hundred supernovas each year. The explosions can be so bright that they outshine their entire galaxy for months. A supernova happens where there is a change in the core, or center, of a star. A change can happen in two different ways. Both result in a supernova. Two Types Of Supernovas The first type of supernova happens when one star pulls matter from another star. Eventually, the stealing star gets too big and explodes, resulting in a supernova. This article is available at 5 reading levels at 2

3 The second type of supernova happens at the end of a star s lifetime. During its life, a star is a balancing act between two forces. The first is the star's own gravity. It tries to squeeze the star into the smallest and tightest ball possible. The second is the tremendous heat and pressure from the star's core, which tries to push all of the star's matter outward. Eventually, the star burns up everything in its core. Then the pressure from the core is no longer as strong as the star's gravity. The star suddenly collapses, or caves in. The collapse happens so fast that it blows the outer part of the star into space at 50 million miles an hour! Only very massive stars will become supernovas. Our sun, for example, is not big enough to become a supernova. The Start Of New Stars, Planets A supernova burns for only a short period of time. Still, scientists can learn a lot from these brief explosions. For example, one type of supernova helped scientists figure out that our universe is expanding at an increasing rate. Scientists have also realized that supernovas are important for distributing elements through the universe. Elements are the basic substances that make up all matter. When a star explodes, it shoots elements into space. These elements travel on to form new stars, planets and everything else in the universe. The huge stars that become supernovas are factories for the raw materials needed to make everything else in the universe. Nearly everything that makes up planets, moons, asteroids, and us is burning inside the core of a star. Ordinary stars don't get hot enough to make the heaviest elements, like gold, silver or lead. Making these requires the pressure and heat of a supernova. Then, the explosion flings all of those elements into space. Eventually, the elements collect and form a new star and new planets. That new solar system then has everything it needs. The elements are the ingredients for making planets like Earth, as well as plants and animals. Anyone Can Find A Supernova NASA scientists use different types of telescopes to look for and study supernovas. Some telescopes observe the light from the explosion. Others observe the energy that the explosion creates. You do not have to be a scientist to hunt for supernovas. You don't even need a telescope. For example, in 2008 a teenager discovered a supernova. Then in January 2011, a 10-year-old girl discovered a supernova while looking at night sky pictures on her computer! This article is available at 5 reading levels at 3

4 Quiz 1 Which paragraph in the section "They Outshine Their Entire Galaxy" explains how many supernovas are seen each year? 2 Which selection from the article BEST describes how supernovas are extremely powerful? (A) (B) (C) (D) When a star explodes, it is called a supernova. It is the largest explosion that happens in space. Eventually, the stealing star gets too big and explodes, resulting in a supernova. The collapse happens so fast that it blows the outer part of the star into space at 50 million miles an hour! Some telescopes observe the light from the explosion. Others observe the energy that the explosion creates. 3 Which two sentences from the article BEST reflect its central ideas? 1. Supernovas are among the most powerful and amazing events in the universe. 2. Most of the changes that take place in the universe happen very, very slowly. 3. A supernova happens where there is a change in the core, or center, of a star. 4. Our sun, for example, is not big enough to become a supernova. (A) 1 and 2 (B) 1 and 3 (C) 2 and 4 (D) 3 and 4 This article is available at 5 reading levels at 4

5 4 Read the following paragraphs from the section "The Start Of New Stars, Planets." The huge stars that become supernovas are factories for the raw materials needed to make everything else in the universe. Nearly everything that makes up planets, moons, asteroids, and us is burning inside the core of a star. Ordinary stars don't get hot enough to make the heaviest elements, like gold, silver or lead. Making these requires the pressure and heat of a supernova. Then, the explosion flings all of those elements into space. How does the information in these paragraphs support a MAIN idea of the article? (A) (B) (C) (D) It explains the role that supernovas play in the development of other items in the universe. It introduces the idea that many planets and stars contain elements like gold, silver and lead. It compares the composition of supernova stars with the composition of other items in space. It highlights how dangerous supernovas can be to other planets, moons and asteroids. This article is available at 5 reading levels at 5