Whale Galaxy

NGC 4631，也称为鲸鱼星系或科德韦尔32，是位于猎犬座以侧面向着我们的螺旋星系。这个星系扭曲成的契形使它的外观看起来像鲱鱼或鲸鱼，因此有了这个昵称。因为这个邻近的星系是以侧面向着地球，专业天文学家可以更好的理解恒星在星系盘面外的分布。

星爆和超星风

NGC 4631的中央包含一个星爆区，这是恒星剧烈生成的区域。来自电离的氢辐射，和被恒星形成爆炸中加热的星际尘埃，是恒星形成的强烈证据。 恒星形成区内，质量最大的恒星只在短时间内进行核聚变，然后他们就爆成为超新星。这么多的超新星在NGC 4631的中心爆炸，他们将星系的气体吹出星系盘面。 这些超级星风可以在X射线和辐射的谱线上看见来自超级星风的气体产生的巨大和高温的晕，发射X射线的气体包围着整个的星系。

尽管在NGC 4631中尚未观测到超新星，但2021年1月29日发现了一颗亮红新星，命名为AT 2021biy（LRN型，星等18.1）。

邻近的星系和星系群

NGC 4631有一个邻近的同伴，矮椭圆星系，NGC 4627。NGC 4627和NGC 4631 一起都列在特殊星系图集当成"双星系"或星系对的例子。

NGC 4631和NGC 4627都是NGC 4631群的一部分，这个星系群还包括交互作用星系NGC 4656和NGC 4657。但是，这个群的确认是有问题的，因为这个星系和其它的星系都未在天空中极为拥挤的一区，对这个星系群成员的估计数量从5到27，所有的研究对这个星系群的成员数量都有不同的认定。

NGC 4631 (also known as the Whale Galaxy or Caldwell 32) is a barred spiral galaxy in the constellation Canes Venatici about 30 million light years away from Earth. It was discovered on 20 March 1787 by German-British astronomer William Herschel. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname. Because this nearby galaxy is seen edge-on from Earth, professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.

Starburst and superwind

NGC 4631 contains a central starburst, which is a region of intense star formation. The strong star formation is evident in the emission from ionized hydrogen and interstellar dust heated by the stars formed in the starburst. The most massive stars that form in star formation regions only burn hydrogen gas through fusion for a short period of time, after which they explode as supernovae. So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This superwind can be seen in X-rays and in spectral line emission. The gas from this superw…

Luminous red nova

Although no supernovae have been observed in NGC 4631 yet, a luminous red nova, designated AT 2021biy (type LRN, mag. 18.1), was discovered by ATLAS on 29 January 2021. The progenitor was either a luminous yellow supergiant or, most likely, a binary with a primary that had a mass of 17-24 M☉. Luminous red novae have two peaks, with the second peak resembling a plateau. The plateau for AT 2021biy had the longest plateau observed to date, with a duration of 210 days.

Nearby galaxies and galaxy group

NGC 4631 has a nearby companion dwarf elliptical galaxy, NGC 4627. NGC 4627 and NGC 4631 together were listed in the Atlas of Peculiar Galaxies as an example of a "double galaxy" or a galaxy pair.

NGC 4631 and NGC 4627 are part of the NGC 4631 Group, a group of galaxies that also includes the interacting galaxies NGC 4656 and NGC 4657. However, exact group identification is problematic because this galaxy and others lie in a part of the sky that is relatively crowded. Estimates of the number of galaxies in this group range from 5 to 27, and all studies identify very different member galaxies for this group.