The universe is simply so vast that it can be difficult to maintain a sense of scale. Many galaxies we see through telescopes such as the NASA/ESA Hubble Space Telescope, the source of this beautiful image, look relatively similar: spiraling arms, a glowing center, and a mixture of bright specks of star formation and dark ripples of cosmic dust weaving throughout.
This galaxy, a spiral galaxy named NGC 772, is no exception. It actually has much in common with our home galaxy, the Milky Way. Each boasts a few satellite galaxies, small galaxies that closely orbit and are gravitationally bound to their parent galaxies. One of NGC 772’s spiral arms has been distorted and disrupted by one of these satellites (NGC 770 — not visible in the image here), leaving it elongated and asymmetrical.
However, the two are also different in a few key ways. For one, NGC 772 is both a peculiar and an unbarred spiral galaxy; respectively, this means that it is somewhat odd in size, shape or composition, and that it lacks a central feature known as a bar, which we see in many galaxies throughout the cosmos — including the Milky Way. These bars are built of gas and stars, and are thought to funnel and transport material through the galactic core, possibly fueling and igniting various processes such as star formation.
Text credit: ESA (European Space Agency)
Image credit: ESA/Hubble & NASA, A. Seth et al.
这个名为NGC 772的螺旋星系也不例外。它和我们的银河系有很多相似之处。每个星系都有几个卫星星系，这些小星系与它们的母星系有着紧密的轨道和引力联系。其中一颗NGC 772的旋臂被其中一颗卫星(NGC 770——图片中不可见)扭曲和破坏，使其拉长且不对称。
文字来源: ESA (European Space Agency)
图片来源: ESA/Hubble & NASA, A. Seth et al.