NASA每日一图 ·

美国国家航空航天局NASA每日一图-2017年8月11日(哈勃显示矮星形螺旋星系)

Hubble Displays a Dwarf Spiral Galaxy

The subject of this NASA/ESA Hubble Space Telescope image is a dwarf galaxy named NGC 5949. Thanks to its proximity to Earth — it sits at a distance of around 44 million light-years from us, placing it within the Milky Way’s cosmic neighborhood — NGC 5949 is a perfect target for astronomers to study dwarf galaxies.

With a mass of about a hundredth that of the Milky Way, NGC 5949 is a relatively bulky example of a dwarf galaxy. Its classification as a dwarf is due to its relatively small number of constituent stars, but the galaxy’s loosely-bound spiral arms also place it in the category of barred spirals. This structure is just visible in this image, which shows the galaxy as a bright yet ill-defined pinwheel. Despite its small proportions, NGC 5949’s proximity has meant that its light can be picked up by fairly small telescopes, something that facilitated its discovery by the astronomer William Herschel in 1801.

Astronomers have run into several cosmological quandaries when it comes to dwarf galaxies like NGC 5949. For example, the distribution of dark matter within dwarfs is quite puzzling (the “cuspy halo” problem), and our simulations of the Universe predict that there should be many more dwarf galaxies than we see around us (the “missing satellites” problem).


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

Last Updated: Aug. 12, 2017
Editor: Karl Hille

哈勃显示矮星形螺旋星系

这个NASA / ESA哈勃太空望远镜图像的主题是一个名为NGC 5949的矮星系,由于它靠近地球 - 它距离我们约4400万光年,距离银河系的宇宙区域 - NGC 5949是天文学家研究矮星系的完美目标。

NGC 5949的质量是银河系的大约百分之一,是矮星系的比较笨重的例子。它的分类是一个矮人是由于其相对较少的组成星星,但星系的松散绑定的螺旋武器也将其置于禁止螺旋的类别。这个结构只是在这个图像中可见,这显示了星系作为明亮但不明确的风车。尽管NGC 5949的距离很小,但是它的接近度意味着它的光线可以被相当小的望远镜所拾取,这有助于它在1801年由天文学家威廉·赫歇尔(William Herschel)发现。

当涉及诸如NGC 5949等矮星系时,天文学家遇到了几个宇宙学的困境。例如,矮人之间的黑暗物质的分布是令人费解的(“光晕”问题),我们对宇宙的模拟预测应该比我们周围看到的更多的矮星系(“丢失的卫星”问题)。


信用:欧空局/哈勃与美国航空航天局
文字信用:欧洲航天局

最后更新:2017年8月12日
编辑:Karl Hille

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