本帖最后由 公爵M16 于 2011-6-23 01:39 编辑
http://www.cnbeta.com/articles/145538.htm
超新星本周成为新闻焦点，最新出版的《自然》杂志有两篇文章就新旧恒星爆炸学说阐述其最新观点。旧的即现代天文学界最近观测到的超新星1987A,最近发生的亮度增加现象表明其经历了进化过程中关键性的转变。新的实际上是一种全新的超新星类型，由四个实例佐证。新类型极度偏向于光谱的蓝色末端，它比Ia型超新星亮10倍，我们还不确定是什么供给它能源。如果有与超新星相关的基础知识的话让我们对这两种理论更易理解。中微子及高能光子的产生表明原星球的毁灭产生了大爆炸，但是伴随爆炸而来的核聚变活动也会产生一些不稳定的放射性同位素，如镍-56和57，以及钛-44，这两者在爆炸式发生时立即产生并持续好多年不散，而残余的超新星主要靠这些同位素衰败时所产生的能量而发光。只有经过几十年，我们才能在超新星位置看到其他的进程-----主要是逐渐扩展的爆炸壳和星球环境之间的相互作用所产生的光亮。
Supernova1987Aoccurred during my second year in college, and my physics professor was so excited that he cancelled our expected lecture on Newtonian mechanics to spend an hour and a half describing why it was so exciting. That excitement was largely based on its proximity in theLarge Magellanic Cloud, only 160,000 light years away, which was already close enough for detailed observations. Since then, observatories have gotten bigger and we got the Hubble Space Telescope up and working, so the situation has only improved, making SN1987A one of the best-studied supernovae around.
超新星1987A是在我大学二年级的时候被发现的，当时我的物理教授非常激动，他甚至取消了我们期待的牛顿力学讲座，花了一个半小时给我们讲解为什么这件事如此激动人心。令人兴奋的地方主要在于超新星附近的大麦哲伦云仅离我们160,000光年，可以进行详细观测。从那时起，我们改善状况，扩建了的天文台，买来哈勃太空望远镜进行工作，使SN1987A成为最受学术关注的超新星之一。
After about 1,500 days from the initial explosion, the supernova is expected to go into a steady decline as the half-life of 44Ti ensures that there's less and less energy being input into the remnant via radioactive decay. And observations show a decline in luminosity of the debris, which centered on the former site of the star. At about 5,000 days post-supernova (November of 2000), however, the predicted decline stopped, and the total luminosity started to rise again. By 8,000 days (April of 2009), the total luminosity was at or above where it was at 3,000 days, depending on the wavelength.
在爆炸1,500天之后，超新星本应该进入钛-44稳定半衰期以确保越来越少的放射性衰败能量输入其爆炸残余部分。观测显示原星球位置为中心的发光体已经减少。然而在超新星爆炸5,000天之后（2000年11月），原预测的减少活动停止，发光体总数又开始上升。8,000天之后（2009年4月），据波长探测，发光体总数不少于超新星爆炸3,000天之后的数量。
What's going on? Observations with the Hubble indicate that it's not the debris itself that is brightening. Instead, a ring of gas that was pushed out of the star's equator about 20,000 years ago (the ring is now about 1.3 light years across). The authors conclude that the brightening is the result of the first remnants of the supernova plowing into this ring, with the resulting collision generating X-rays that are lighting up more of the gas. This sort of behavior has been predicted for some time, but this represents the first time it has been observed.
究竟是怎么回事？哈勃望远镜观测表明不是爆炸残骸本身在发光，而是一条围绕着星球的环状气团，该气团约20,000年前被挤出星际赤道（气团直径现在约 1.3光年）。作者得出结论，亮度增加是由于超新星第一次爆炸的残骸进入气团并碰撞产生X-射线，点亮了更多气团。这种现象早就被预测到了，但被观察到还是第一次。
Not everything in space is going quite according to predictions though. The fact that most supernovae are initially powered by the decay of some specific radioactive isotopes allows us to make very specific predictions about what the timing of luminosity should be. A survey of supernovae run at the Palomar Observatory has now identified four objects that don't fit the expected pattern. A study of the light that came off these events show that they all share common properties.
虽然并不是空间的一切事物都会完全按照预测来运行，但事实上大多数超新星最初是以一些特殊放射性同位素的衰败为动力的。因此，我们就能够具体的预计出观测发光体的时机。帕洛玛天文台的一项超新星调查显示，已经有四个星体与预期的类型不一致。通过对这些活动产生的光线的研究，发现它们具有共同的性质。
One of them is that their luminosity is heavily biased to the UV portion of the spectrum, and they're unusually bright. To get the luminosity from the decay of 56Ni, the explosion would have had to produce several solar masses of that alone. The decline in luminosity is also much faster than we'd expect based on half lives of the common isotopes. "These are therefore not radioactively powered events," the authors conclude. To bea product of the explosion itself would require what they term "an unrealistic total explosion energy."
共同性质之一是它们的发光体极度偏向于光谱的紫外线部分，异常明亮。为了从镍-56的衰败中得到发光体，爆炸就必须单独产生几倍于太阳质量的发光体。而这些发光体的衰退速度比普通同位素半衰期的衰退速度要快的多。作者总结说：“因此，这些不是以物质放射为动力的活动。”成为爆炸后的产物，其本身需要物理学家所说的“不现实的爆炸总能源”
Finally, the spectrum of the light seems to indicate the light is coming from material that is extremely hydrogen-poor, which rules out some form of a rapid collision analogous to the one observed in SN1987A.
最终对这种光进行光谱分析得出，它来自于极度贫氢的物质。这种物质，没有了极速碰撞的某些形态，与在SN1987A上观测到的结构极为相似。
So, just about all of our common expectations about supernovae aren't working out. The authors suggest two possible explanations. One is the explosion of a star of over 90 solar masses, which will often expel a hydrogen-poor shell shortly before dying. If the time difference between this expulsion and the explosion is short enough, debris will impact the shell days after the explosion itself, creating the effect seen here. The alternative is that the remains of the star are injecting energy into the debris. This could happen if these supernovae produced a rapidly spinning magnetar.
因此，我们对于超新星的期望几乎都没有达到。作者给出了两种可能的解释：一是，一个90倍于太阳质量的星体爆炸，会在其自身毁灭前释放出贫氢壳。如果爆炸和释放间的时间足够短的话，残骸会在爆炸几天后撞击贫氢壳而形成我们看到的效应；另一种是星体残余向残骸中注入能量，然而只有在这些超新星产生出一个飞速旋转的磁星时，这种现象才会出现。
The Palomar team has identified four of these items in about two years of observations, so it's possible that we'll be able to spot a few more and get a better sense of what's happening. Otherwise, we may have to wait a bit to get lucky enough to observe one from a shorter distance.
帕洛玛团队经过约两年的观测识别出了这些类别中的四种，因此我们也有可能再找出一些其他的证据来感知其动态。要不然我们就只有等，等到足够幸运的时候，在较近的地方观测到一个。 |
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