Pinwheel Galaxy, M101

Galaxy M101, popularly known as the Pinwheel Galaxy, is one of the best known spiral galaxies. It is 23 million light years in distance. The above photo was released on 28 February, 2006.

银河系M101，俗称Pinwheel Galaxy，是著名的螺旋星系之一。它距离地球2300万光年。上述照片于2006年2月28日发布。

The Pinwheel Galaxy has attracted more attention because of the discovery of a Type 1a supernova nearby on August 24, 2011. The discovery was made at the Palomar Observatory in California. Mark Sullivan of Oxford comments that they found it probably 12 hours after the start of the event. It is the first close Type 1a supernova observed since 1972. Having such a close Type 1a to study will allow comparisons to Cepheid variables in the same galaxy, which can sharpen our characterization of the Cepheids as a distance scale.(Science News Sep 24, 2011,p5)

Pinwheel星系因其2011年8月24日发现的一颗Type 1a超新星而受到更多关注。该发现是在加利福尼亚州的帕洛马天文台做出的。Oxford的Mark Sullivan评论说，他们可能在事件开始后12小时发现了它。这是自1972年以来首次观测到如此接近的Type 1a超新星。拥有这样接近的Type 1a超新星进行研究，将允许与同一星系中的造父变星进行比较，从而更精确地刻画造父变星作为距离标尺的特性。（Science News 2011年9月24日，第5页）

"The giant spiral disk of stars, dust, and gas is 170,000 light-years across or nearly twice the diameter of our galaxy, the Milky Way. M101 is estimated to contain at least one trillion stars. Approximately 100 billion of these stars could be like our Sun in terms of temperature and lifetime.

那个由恒星、尘埃和气体组成的巨大螺旋盘直径约为170,000光年，或 nearly 两倍于我们的银河系直径。M101估计至少包含一万亿颗恒星。其中大约有1000亿颗恒星在温度和寿命方面与我们的太阳相似。

The galaxy's spiral arms are sprinkled with large regions of star-forming nebulae. These nebulae are areas of intense star formation within giant molecular hydrogen clouds. Brilliant young clusters of hot, blue, newborn stars trace out the spiral arms. The disk of M101 is so thin that Hubble easily sees many more distant galaxies lying behind the galaxy.

银河的旋臂中散布着大量恒星形成的星云。这些星云是巨大分子氢云中剧烈恒星形成的区域。明亮的年轻恒星群，这些恒星炽热、蓝色且刚诞生，勾勒出旋臂的轮廓。M101的盘面非常薄，因此哈勃能够看到许多更遥远的星系位于其背后。

M101 lies in the northern circumpolar constellation, Ursa Major (The Great Bear), at a distance of 23 million light-years from Earth. The galaxy fills a region in the sky equal to one-fifth the area of the full moon."

The newly composed image was assembled from Hubble archived images taken with the Advanced Camera for Surveys and the Wide Field and Planetary Camera 2 over nearly 10 years: in March 1994, September 1994, June 1999, November 2002, and January 2003. The Hubble exposures have been superimposed onto ground-based images, visible at the edge of the image, taken at the Canada-France-Hawaii Telescope in Hawaii, and at the 0.9-meter telescope at Kitt Peak National Observatory, part of the National Optical Astronomy Observatory in Arizona. The final color image was assembled from individual exposures taken through blue, green, and red (infrared) filters."(from Hubble photo release)

新合成的图像由哈勃空间望远镜使用先进巡天相机和宽场行星摄相机在近10年间拍摄的存档图像组成：1994年3月、1994年9月、1999年6月、2002年11月和2003年1月。这些哈勃望远镜的曝光数据已叠加到地面望远镜拍摄的图像上，这些图像在图像边缘可见，是在夏威夷的加拿大-法国-夏威夷望远镜以及亚利桑那州国家光学天文台的0.9米望远镜上拍摄的。最终的彩色图像由通过蓝、绿和红（红外）滤光片拍摄的单张曝光图像合成。

M101位于北天极星座大熊座（The Great Bear）中，距离地球2300万光年。这个星系在天空中占据的区域面积相当于满月的五分之一。