adapted from What Is a Supernova? by NASA A supernova is the explosion of a star. It is the largest explosion that takes place in space. Where Do Supernovas Take Place? Supernovas are often seen in other galaxies, but are difficult to see in our own Milky Way galaxy because dust blocks our view. In 1604, Johannes Kepler discovered the last observed supernova in the Milky Way. NASA's Chandra telescope discovered the remains of a more recent supernova. It exploded in the Milky Way more than a hundred years ago. What Causes a Supernova? A supernova happens where there is a change in the core, or center, of a star. A change can occur in two different ways, with both resulting in a supernova. The first type of supernova happens in binary star systems, which are systems where two stars orbit the same point. One of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova. The second type of supernova occurs at the end of a single star's lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force and the core collapses, resulting in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova. Why Do Scientists Study Supernovas? A supernova burns for only a short period of time, but it can tell scientists a lot about the universe. One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate. Scientists also have determined that supernovas play a key role in distributing elements throughout the universe. When the star explodes, it shoots elements and debris into space. Many of the elements we find here on Earth are made in the core of stars. These elements travel on to form new stars, planets and everything else in the universe. How Do NASA Scientists Look for Supernovas? NASA scientists use different types of telescopes to look for and study supernovas. Some telescopes are used to observe the visible light from the explosion and others record data from the X-rays and gamma rays that are also produced. Both NASA's Hubble Space Telescope and Chandra X-ray Observatory have captured images of supernovas. 1 Read the sentences from the passage. "Scientists also have determined that supernovas play a key role in distributing elements throughout the universe. When the star explodes, it shoots elements and debris into space." Which phrase from the sentences provides the best clue about the meaning of the word debris? A. "have determined" B. "distributing elements" C. "into space" D. "star explodes"

 A supernova is the explosion of a star. It is the largest explosion that takes place in space.

 Supernovas are often seen in other galaxies, but are difficult to see in our own Milky Way galaxy because dust blocks our view. In 1604, Johannes Kepler discovered the last observed supernova in the Milky Way. NASA's Chandra telescope discovered the remains of a more recent supernova. It exploded in the Milky Way more than a hundred years ago.

 A supernova happens where there is a change in the core, or center, of a star. A change can occur in two different ways, with both resulting in a supernova.

 The first type of supernova happens in binary star systems, which are systems where two stars orbit the same point. One of the stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter. Having too much matter causes the star to explode, resulting in a supernova.

 The second type of supernova occurs at the end of a single star's lifetime. As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core is so heavy that it cannot withstand its own gravitational force and the core collapses, resulting in the giant explosion of a supernova. The sun is a single star, but it does not have enough mass to become a supernova.

 A supernova burns for only a short period of time, but it can tell scientists a lot about the universe.

 One kind of supernova has shown scientists that we live in an expanding universe, one that is growing at an ever increasing rate.

 Scientists also have determined that supernovas play a key role in distributing elements throughout the universe. When the star explodes, it shoots elements and debris into space. Many of the elements we find here on Earth are made in the core of stars. These elements travel on to form new stars, planets and everything else in the universe.

 NASA scientists use different types of telescopes to look for and study supernovas. Some telescopes are used to observe the visible light from the explosion and others record data from the X-rays and gamma rays that are also produced. Both NASA's Hubble Space Telescope and Chandra X-ray Observatory have captured images of supernovas.