这幅图片可能让第一次看到它的人们不敢相信自己的眼睛，特别是当涉及象星系和星云一样的天体时。 这张图片的上半部是由哈勃太空望远镜
拍摄的螺旋星云（编号NGC7293，位于宝瓶座内）真实照片，下半部是科学家用超级计算机模拟的从侧面看螺旋星云的模拟图。因为这些观测对象如此之远以致于天文学家不能看见他们的立体结构。
例如螺旋形星云，在这张丰富多彩的图像中它类似一个炸面包圈。它是一颗即将死亡的恒星抛出的气体外壳，这个复杂的天体的更早期的图像，那些气体外壳由于距离我们太远，不允许天文学家明确解释它的细致结构。
一种可能的解释是这种螺旋形的形式象一种象蛇一样的线圈。
最近，一个支天文学家的小队， 以O'Dell为领导，包括C.罗伯特荒德比大学在内，使用从哈勃望远镜先进照像机拍摄到的最新图象中并利用超级计算机模拟了
一个从侧面看螺旋星云的模拟图。
象螺旋星云一样的行星状星云，是一个专业和业余天文学家的最喜爱的观测目标。天文学家们希望，这次新的观察角度将解释象我们太阳大小的恒星在即将凋谢之际怎样将气体的外壳抛出，形成行星状星云那样的复杂形状的。这个最新的
研究结果将在11月号的《天文学》杂志中刊登出来。
A New Twist on an Old Nebula
Looks can be deceiving, especially when it comes to celestial objects like galaxies and nebulas. These objects are so far away that astronomers cannot see their three-dimensional structure. The Helix Nebula, for example, resembles a doughnut in colorful images. Earlier images of this complex object — the gaseous envelope ejected by a dying, sun-like star — did not allow astronomers to precisely interpret its structure. One possible interpretation was that the Helix's form resembled a snake-like coil.
Now, a team of astronomers using observations from several observatories, including NASA's Hubble Space Telescope, has established that the Helix's structure is even more perplexing. Their evidence suggests that the Helix consists of two gaseous disks nearly perpendicular to each other 。
team of astronomers, led by C. Robert O'Dell of Vanderbilt University in Nashville, Tenn., made its finding using highly detailed images from the Hubble telescope's Advanced Camera for Surveys, pictures from Cerro Tololo Inter-American Observatory in Chile, and measurements from ground-based optical and radio telescopes which show the speed and direction of the outflows of material from the dying star. The Helix, the closest planetary nebula to Earth, is a favorite target of professional and amateur astronomers. Astronomers hope this finding will provide insights on how expelled shells of gas from dying stars like our Sun form the complex shapes called planetary nebulas. The results are published in the November issue of the Astronomical Journal. |
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