Which stars undergo supernova explosions

Instead, they show a lot of carbon and oxygen, which is the composition of a white dwarf. The maximum mass for a white dwarf is 1. White dwarfs of nearly the Chandrasekhar mass are essentially identical, so they undergo nearly identical explosions. The most popular theory for turning a white-dwarf star into a supernova is through an act of stellar cannibalism. If a white dwarf has a close companion star, it might steal gas from the companion's surface.

If the amount of material accumulated by the white dwarf pushes its mass near the Chandrasekhar limit, the white dwarf might explode, leaving nothing behind. Crab Nebula supernova remnant The stars that make Type II supernovae, on the other hand, probably are born in a galaxy's spiral arms -- regions that are populated by lots of young, bright stars -- and don't live long enough to wander from their birthplaces. Because they are short-lived, such stars also must be massive.

The brightness of a typical Type II supernova peaks after a week or two and remains nearly constant for up to two months. Another fainter supernova was seen in The next supernova became visible in November and, being brighter than the planet Venus, was quickly spotted by a number of observers, including the young Tycho Brahe see Orbits and Gravity. He correctly deduced that it must be a phenomenon belonging to the realm of the stars, not of the solar system. Kepler wrote a book about his observations that was read by many with an interest in the heavens, including Galileo.

No supernova has been spotted in our Galaxy for the past years. Since the explosion of a visible supernova is a chance event, there is no way to say when the next one might occur. At their maximum brightness, the most luminous supernovae have about 10 billion times the luminosity of the Sun. For a brief time, a supernova may outshine the entire galaxy in which it appears.

At the time of their outbursts, supernovae eject material at typical velocities of 10, kilometers per second and speeds twice that have been observed. A speed of 20, kilometers per second corresponds to about 45 million miles per hour, truly an indication of great cosmic violence. Supernovae are classified according to the appearance of their spectra, but in this chapter, we will focus on the two main causes of supernovae.

Type Ia supernovae are ignited when a lot of material is dumped on degenerate white dwarfs Figure 2 ; these supernovae will be discussed later in this chapter. For now, we will continue our story about the death of massive stars and focus on type II supernovae, which are produced when the core of a massive star collapses. Figure 2: Supernova J. This image of supernova J, located in Messier 82 M82 , which is also known as the Cigar galaxy, was taken by the Hubble Space Telescope and is superposed on a mosaic image of the galaxy also taken with Hubble.

The supernova event is indicated by the box and the inset. This explosion was produced by a type Ia supernova, which is theorized to be triggered in binary systems consisting of a white dwarf and another star—and could be a second white dwarf, a star like our Sun, or a giant star.

This type of supernova will be discussed later in this chapter. At a distance of approximately In the image, you can see reddish plumes of hydrogen coming from the central region of the galaxy, where a considerable number of young stars are being born.

Our most detailed information about what happens when a type II supernova occurs comes from an event that was observed in Before dawn on February 24, Ian Shelton, a Canadian astronomer working at an observatory in Chile, pulled a photographic plate from the developer. Where he expected to see only faint stars, he saw a large bright spot.

Concerned that his photograph was flawed, Shelton went outside to look at the Large Magellanic Cloud. He soon realized that he had discovered a supernova, one that could be seen with the unaided eye even though it was about , light-years away. The supernova remnant with its inner and outer red rings of material is located in the Large Magellanic Cloud.

This image is a composite of several images taken in , , and —about a decade after supernova A was first observed. Now known as SN A, since it was the first supernova discovered in , this brilliant newcomer to the southern sky gave astronomers their first opportunity to study the death of a relatively nearby star with modern instruments.

It was also the first time astronomers had observed a star before it became a supernova. The star that blew up had been included in earlier surveys of the Large Magellanic Cloud, and as a result, we know the star was a blue supergiant just before the explosion.

By combining theory and observations at many different wavelengths, astronomers have reconstructed the life story of the star that became SN A. Formed about 10 million years ago, it originally had a mass of about 20 M Sun. At this time, its luminosity was about 60, times that of the Sun L Sun , and its spectral type was O.

Type Ia supernovae are generally thought to originate from white dwarf stars in a close binary system. As the gas of the companion star accumulates onto the white dwarf, the white dwarf is progressively compressed, and eventually sets off a runaway nuclear reaction inside that eventually leads to a cataclysmic supernova outburst.

Astronomers use Type Ia supernovas as " standard candles " to measure cosmic distances because all are thought to blaze with equal brightness at their peaks. Type Ib and Ic supernovas also undergo core-collapse just as Type II supernovas do, but they have lost most of their outer hydrogen envelopes. In , scientists detected the faint, hard-to-locate companion star to a Type Ib supernova. The search consumed two decades , as the companion star shone much fainter than the bright supernova.

Recent studies have found that supernovas vibrate like giant speakers and emit an audible hum before exploding. In , scientists caught a supernova in the act of exploding for the first time.

While peering at her computer screen, astronomer Alicia Soderberg expected to see the small glowing smudge of a month-old supernova.

But what she and her colleague saw instead was a strange, extremely bright, five-minute burst of X-rays. With that observation, they became the first astronomers to catch a star in the act of exploding. The new supernova was dubbed SN D. When supernovae explode, they jettison matter into space at some 9, to 25, miles 15, to 40, kilometers per second. These blasts produce much of the material in the universe—including some elements, like iron, which make up our planet and even ourselves.

Heavy elements are only produced in supernovae, so all of us carry the remnants of these distant explosions within our own bodies. Supernovae add enriching elements to space clouds of dust and gas, further interstellar diversity, and produce a shock wave that compresses clouds of gas to aid new star formation. But only a select few stars become supernovae. Many stars cool in later life to end their days as white dwarfs and, later, black dwarfs.

But massive stars, many times larger than our own sun, may create a supernova when their core's fusion process runs out of fuel. Star fusion provides a constant outward pressure, which exists in balance with the star's own mass-driven, inward gravitational pull.

When fusion slows, outbound pressure drops and the star's core begins to condense under gravity—becoming ever denser and hotter. To outward appearances, such stars begin growing, swelling into bodies known as red supergiants. But at their cores, shrinking continues, making a supernova imminent.

When a star's core contracts to a critical point, a series of nuclear reactions is unleashed. This fusion staves off core collapse for a time—but only until the core is composed largely of iron, which can no longer sustain star fusion.

In a microsecond, the core may reach temperatures of billions of degrees Celsius. Iron atoms become crushed so closely together that the repulsive forces of their nuclei create a recoil of the squeezed core—a bounce that causes the star to explode as a supernova and give birth to an enormous, superheated, shock wave.

Supernovae also occur in binary star systems.