返回信息流15-Nov-2007: The NASA/ESA Hubble Space Telescope has probed the bright core of Comet 17P/Holmes which, to the delight of sky watchers, mysteriously brightened by nearly a million-fold in a 24-hour period beginning October 23, 2007.
Astronomers have used Hubble’s powerful resolution to study Comet Holmes’ core for clues about how the comet brightened. The orbiting observatory’s Wide Field Planetary Camera 2 (WFPC2) monitored the comet for several days, snapping images on 29 Oct., 31 Oct. and 4 Nov. Hubble’s crisp “eye” can see details as small as 54 kilometres across, providing the sharpest view yet of the source of the spectacular brightening.
The Hubble image at right, taken on 4 Nov., shows the heart of the comet. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a “bow tie” appearance.
The composite colour image at left, taken Nov. 1 by the amateur astronomer Alan Dyer, shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet’s right side.
The nucleus — the small solid body that is the source of the comet’s activity — is still swaddled in bright dust, even 12 days after the spectacular outburst. “Most of what Hubble sees is sunlight scattered from microscopic particles,” explained Hal Weaver of The Johns Hopkins University Applied Physics Laboratory of Laurel, Maryland in the USA, who led the Hubble investigation. “But we may finally be starting to detect the emergence of the nucleus itself in this final Hubble image.”
Hubble first observed Comet 17P/Holmes on June 15, 1999, when there was virtually no dusty shroud around the nucleus. Although Hubble cannot resolve the nucleus, astronomers inferred its size by measuring its brightness. Astronomers deduced that the nucleus’s diameter was approximately 3.4 kilometres, about the distance between the Arc de Triomphe and the Louvre glass pyramid in Paris. They hope to use the new Hubble images to determine the size of the comet’s nucleus to see how much of it was blasted away during the outburst.
Hubble’s two earlier snapshots of Comet Holmes also showed some interesting features. On 29 Oct. the telescope spied three “spurs” of dust emanating from the nucleus while the Hubble images taken on 31 Oct. revealed an outburst of dust just west of the nucleus.
The Hubble images however do not show any large fragments near the nucleus of Comet Holmes, unlike the case of Comet 73P/Schwassmann-Wachmann 3 (SW3). In the spring of 2006 Hubble observations revealed a multitude of “mini-comets” ejected by SW3 after the comet increased dramatically in brightness. Ground-based images of Comet Holmes show a large, spherically symmetrical cloud of dust that is offset from the nucleus, suggesting that a large fragment broke off and subsequently disintegrated into tiny dust particles after moving away from the main nucleus. Unfortunately, the huge amount of dust near the comet’s nucleus and the relatively large distance from Earth (240 million kilometres, or 1.6 astronomical units for Holmes versus 15 million kilometres, 0.1 astronomical units for SW3), conspire to make detecting fragments near Holmes nearly impossible right now, unless the fragments are nearly as large as the nucleus itself.
Notes for editors:
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency.
The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.
The Hubble Comet Holmes observing team comprises H. Weaver and C. Lisse (The Johns Hopkins University Applied Physics Laboratory); P. Lamy (Laboratoire d’Astrophysique de Marseille, France); I. Toth (Konkoly Observatory, Hungary); M. Mutchler (Space Telescope Science Institute); W. Reach (California Institute of Technology); and J. Vaubaillon (California Institute of Technology).
Credit for Hubble image: NASA, ESA, and H. Weaver (The Johns Hopkins University Applied Physics Laboratory)
Credit for ground-based image: A. Dyer, Alberta, Canada
这是一条镜像帖。来源：北邮人论坛 / astronomy / #2101同步于 2007/11/22
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哈勃观测17P/Holmes彗星慧核，揭秘突然发光
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2007/11/22镜像同步17 回复
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【 在 p044313039 的大作中提到: 】
: 大姐给翻译下吧，也好检测下自己的专业英语水平 >_<
为了这句话我译了，顺便练考研翻译
15-11-2007：NASA/ESA 哈勃太空望远镜观测到17P/Holmes彗星的彗核从2007年10月23日起的24小时内光度奇迹般地增大了近百万倍，这是令观星者们感到欣喜若狂的。
天文学家们用哈勃强大的分辨能力去研究Holmes彗核以探明这颗彗星为何爆发。轨道天文台的第二代广角及行星相机已经对它监控了几天，并且拍下了10月29日和30日的照片。哈勃能捕捉到54千米范围内的细节，使它能为这次华丽的爆发提供最精细的观测。
右边的哈勃图像拍摄于11月4日，显示了这颗彗星的心脏。这张图片的彗核部分经过了特别处理以突出核心周围的尘埃分布。沿东西方向（水平方向）的尘埃大约是沿南北方向（垂直方向）尘埃的两倍，使得彗星外观看起来像个“蝴蝶结领结”。
左边的合成彩色图像于11月1日由业余天文学家Alan Dyer拍摄，展示了整个彗发的复杂结构，包含了同心尘埃壳和从彗星右侧发射出的黯淡彗尾。
彗核——构成彗星一切活动的最终来源的小固体核——仍然在亮尘埃的包裹之中，即使是在这次华丽爆发的12天之后。“哈勃看到的大多是微粒散射的太阳光，”这次哈勃观测的指挥者、来自Laurel，Md Johns Hopkins大学应用物理实验室的Hal Weaver说，“但是我们可能最终还是会开始在最后的哈勃图像中探查到彗核的凸现。”
哈勃首次发现17P/Holmes彗星是在1999年，那时实际上并没有尘埃层覆盖彗核。尽管哈勃并不能观察到彗核，但是天文学家们可以通过测量它的光度来推断彗核的大小。天文学家们推算出彗核直径大约3.4公里，差不多是凯旋门到巴黎卢浮宫玻璃金字塔的距离。他们希望用新的哈勃图像来确定彗核的大小，以了解爆发期间它被轰走了多少。
两张Holmes彗星的早期哈勃快照也显示了它一些有趣的特征。在10月29日望远镜发现从彗核发射出三个“突起物”，而10月31日正好在彗核的西方出现了一次爆发。
然而Holmes彗星的哈勃图像并没有显示出任何彗核附近大的碎片，这不同于Comet 73P/Schwassmann-Wachmann 3 (SW3)彗星的例子。2006年春天哈勃观测资料显示出SW3彗星光度急剧增大后喷射出许多“迷你彗星”。地面观测到的Holmes彗星图像显示出一个偏移彗核的巨大球形均匀尘埃云，暗示了有一个大碎片分裂开了并且随后在分离主彗核时碎裂成微小的尘埃粒子。不幸的是，大量的尘埃都邻近彗核并相对地球非常遥远（2.4亿公里，或者1.6个天文单位，与之相对的SW3是0.15亿公里或0.1个天文单位），加起来使现在探测到Holmes附近的碎片几乎不可能，除非碎片跟彗核差不多大。
（后面的Notes for editors就不用译了吧）
【 在 orlandozp 的大作中提到: 】
: 为了这句话我译了，顺便练考研翻译
: 15-11-2007：NASA/ESA 哈勃太空望远镜观测到17P/Holmes彗星的彗核从2007年10月23日起的24小时内光度奇迹般地增大了近百万倍，这是令观星者们感到欣喜若狂的。
: 天文学家们用哈勃强大的分辨能力去研究Holmes彗核以探明这颗彗星为何爆发。轨道天文台的第二代广角及行星相机已经对它监控了几天，并且拍下了10月29日和30日的照片。哈勃能捕捉到54千米范围内的细节，使它能为这次华丽的爆发提供最精细的观测。
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