美国国家航空航天局NASA每日一图-2017年7月24日

Hubble’s Hunting Dog Galaxy

Tucked away in the small northern constellation of Canes Venatici (The Hunting Dogs) is the galaxy NGC 4242, shown here as seen by the NASA/ESA Hubble Space Telescope. The galaxy lies some 30 million light-years from us. At this distance from Earth, actually not all that far on a cosmic scale, NGC 4242 is visible to anyone armed with even a basic telescope, as British astronomer William Herschel found when he discovered the galaxy in 1788.

This image shows the galaxy’s bright center and the surrounding dimmer and more diffuse “fuzz.” Despite appearing to be relatively bright in this image, studies have found that NGC 4242 is actually relatively dim (it has a moderate-to-low surface brightness and low luminosity) and also supports a low rate of star formation. The galaxy also seems to have a weak bar of stars cutting through its asymmetric center, and a very faint and poorly-defined spiral structure throughout its disk. But if NGC 4242 is not all that remarkable, as with much of the Universe, it is still a beautiful and ethereal sight.


Image credit: ESA/Hubble & NASA
Text credit: European Space Agency

Last Updated: July 24, 2017
Editor: Karl Hille

哈勃的猎犬银河

藏在Canes Venatici(狩猎犬)的小北部星座是星系NGC 4242,如NASA / ESA哈勃太空望远镜所示。银河系距离我们约三千万光年。在远离地球的地球上,实际上并不是所有这些都远远超出了宇宙的规模,NGC 4242对于拥有甚至基本望远镜的人都是可见的,正如英国天文学家威廉·赫歇尔(William Herschel)1788年发现的那个星系所发现的那样。

该图像显示了星系的明亮中心和周围的调光器,并且更加漫散的“绒毛”。尽管在这幅图像中看起来相对较亮,但是研究发现,NGC 4242实际上相对较暗(它具有中等到低的表面亮度和低亮度),并且还支持较低的恒星形成速率。星系也似乎有一个弱的星星穿过其不对称的中心,在整个磁盘上都有一个非常微弱而不太明确的螺旋结构。但如果NGC 4242并不是那么出色,就像宇宙中的大部分,它仍然是一个美丽和飘渺的景象。


图片来源:ESA /哈勃与美国航空航天局
文字信息:欧洲航天局

最后更新:2017年7月24日
编辑:Karl Hille

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