- 站在巨人的肩膊上Lv 61 十年前最愛解答
恆星演化未期的星體爆炸。質量 > 4 太陽質量的恆星，繼續燃燒越來越重的元素直至鐵 (iron) - 原子核束縳得最緊的元素。由於不能通過聚合鐵而產生更多的能量，形成惰性的鐵核心，不能再產生能量，恆星核心不能抵抗重力的收縮，迅速地塌縮，即使電子簡併壓力亦不能抗衡重力，核心收縮得越來越快，密度越來越高，當密度達至 1014 g/cc，核子被擠壓在一起，因而產生強大的反抗力，核心頓時變得非常堅硬。急速的塌縮撞落核心，內部產生極強大的反衝，以激振波 (shock wave) 向外傳播，並在外層觸發核反應，結果外層發生能量極高的爆炸 (相等於 1028 噸 TNT)，恆星的外層在極短時間內完全炸毀。恆星的亮度突然增加很多個星等。例如：中國宋代 (1054 AD) 天文學家記錄位於金牛座的「客星」，肉眼於日間也能看見，一個月後才漸漸變暗，兩年後才完全消失。
2006-12-25 13:09:17 補充：
2006-12-25 13:13:59 補充：
2006-12-25 13:14:50 補充：
Supernovae (the plural of supernova) are extremely important for understanding our Galaxy. They heat up the interstellar medium, distribute heavy elements throughout the Galaxy, and accelerate cosmic rays. But just what is a supernova? And is there more than one type?
2006-12-25 13:15:59 補充：
Indeed, there seems to be two distinct types of supernovae -- those which occur for a single massive star and those which occur because of mass transfer onto a white dwarf in a binary system.
2006-12-25 13:16:23 補充：
As you will see, however, it is only what gets the process started toward the explosion which differs between the two types.Supernovae from Single, Massive Stars The Life Cycle of a Massive Star
2006-12-25 13:17:34 補充：
Stars which are 8 times or more massive than our Sun end their lives in a most spectacular way; they go supernova
2006-12-25 13:17:53 補充：
. A supernova explosion will occur when there is no longer enough fuel for the fusion process in the core of the star to create an outward pressure which combats the inward gravitational pull of the star's great mass. First, the star will swell into a red supergiant...at least on the outside.
2006-12-25 13:18:38 補充：
On the inside, the core yields to gravity and begins shrinking. As it shrinks, it grows hotter and denser. A new series of nuclear reactions begin to occur....temporarily halting the collapse of the core... but alas, it is only temporary.
2006-12-25 13:19:01 補充：
When the core contains essentially just iron, it has nothing left to fuse (because of iron's nuclear structure, it does not permit its atoms to fuse into heavier elements). Fusion in the core ceases. In less than a second, the star begins the final phase of gravitational collapse.
2006-12-25 13:19:23 補充：
The core temperature rises to over 100 billion degrees as the iron atoms are crushed together. The repulsive force between the nuclei overcomes the force of gravity. So the core compresses, but then recoils.
2006-12-25 13:19:58 補充：
The energy of the recoil is transferred to the envelope of the star, which then expodes and produces a shock wave.
2006-12-25 13:20:27 補充：
As the shock encounters material in the star's outer layers, the material is heated, fusing to form new elements and radioactive isotopes. The shock then propels the matter out into space. The material that is exploded away from the star is now known as a supernova remnant.
2006-12-25 13:21:00 補充：
Cygnus Loop in X-rays Crab Nebula in X-rays All that remains of the original star is a small, super-dense core composed almost entirely of neutrons -- a neutron star.
2006-12-25 13:21:44 補充：
Or, if the original star was very massive indeed (say 15 or more times the mass of our Sun), even the neutrons cannot survive the core collapse...and a black hole forms.
- Alpha WLv 71 十年前
A supernova is a stellar explosion which produces an extremely bright object made of plasma that declines to invisibility over weeks or months. A supernova briefly outshines its entire host galaxy. It would take 10 billion years for the Sun to produce the energy output of an ordinary Type II supernova. Stars beneath the Chandrasekhar limit, such as the Sun, are too light to ever become supernovae and will evolve into white dwarfs.
Multiwavelength X-ray image of the remnant of Kepler's Supernova, SN 1604. (Chandra X-ray Observatory)