As nuclear fusion engines, most stars live placid lives for hundreds of millions to billions of years. But near the end of their lives they can turn into crazy whirligigs, puffing off shells and jets of hot gas. In this image NGC 7027 resembles a jewel bug, an insect with a brilliantly colorful metallic shell.
Recently, NGC 7027’s central star was identified in a new wavelength of light — near-ultraviolet — for the first time by using Hubble’s unique capabilities. The near-ultraviolet observations will help reveal how much dust obscures the star and how hot the star really is. This object is a visibly diffuse region of gas and dust that may be the result of ejections by closely orbiting binary stars that were first slowly sloughing off material over thousands of years, and then entered a phase of more violent and highly directed mass ejections. Hubble first looked at this planetary nebula in 1998. By comparing the old and new Hubble observations, researchers now have additional opportunities to study the object as it changes over time. Planetary nebulas are expanding shells of gas created by dying stars that are shedding their outer layers. When new ejections encounter older ejections, the resulting energetic collisions shape the nebula. The mechanisms underlying such sequences of stellar mass expulsion are far from fully understood, but researchers theorize that binary companions to the central, dying stars play essential roles in shaping them. NGC 7027 is approximately 3,000 light-years away in the constellation Cygnus.
最近，通过利用哈勃望远镜的独特功能，NGC 7027的中央恒星首次被识别出了一种新的光波长——近紫外线。近紫外线的观测将有助于揭示有多少尘埃遮蔽了这颗恒星，以及这颗恒星的真实温度。这个物体是一个可见的气体和尘埃扩散区域，可能是由紧密绕行的双星恒星的喷射所致，这些双星在几千年的时间里首先缓慢地剥离物质，然后进入了更猛烈和高度定向的质量喷射阶段。哈勃望远镜于1998年首次观察了这个行星状星云。通过比较新旧哈勃望远镜的观测结果，研究人员现在有了更多的机会来研究这个随着时间变化的物体。行星状星云是由濒死的恒星正在脱落其外层而产生的膨胀的气体外壳。当新的喷出物遇到旧的喷出物时，产生的高能碰撞形成了星云。这种恒星质量排出序列背后的机制还远未被完全理解，但研究人员理论化地认为，与中心濒死恒星相伴的双星在形成它们的过程中发挥了重要作用。NGC 7027距离我们约3000光年，位于天鹅座。NGC 7027距离我们约3000光年，位于天鹅座。
影像来源：NASA, ESA and J. Kastner (RIT)