In the following eight billion years , in contrast , galactic mergers became much less common , the gargantuan black holes went dormant , and star formation slowed to a flicker 相对之下，接下来的80亿年，星系的合并变得较不普遍，巨大的黑洞蛰伏休眠，恒星的形成则少得可怜。
Because they are rearranging the interstellar matter that is the raw material for further star formation , they may affect the rate of star formation in a galaxy 星群爆发意味着重组星际物质，而这些星际物质恰恰是新星形成的原料，因此，星群爆发可能影响星系中新星形成的速度。
The hurricane blast of stellar winds and blistering ultravioletradiation within the cavity is now compressing the surrounding walls ofcold hydrogen . this is triggering a second stage of new star formation 空穴中星风的击波和炽热的紫外线辐射正在压缩周围冷氢气形成的墙。由此触发了第二阶段新恒星的形成。
Because high - mass stars live for only a few tens of millions of years ? a short time by galactic standards ? their number closely tracks variations in the galaxy ' s overall star formation rate 由于大质量恒星只能存活数千万年，这在星系的标准看来算是很短的时间，因此它们的数量很适合用来追踪星系中恒星形成率的整体变化。
Hubble has found that whereas supernovae occur throughout the regions of star formation in galaxies , long - duration grbs are concentrated in the very brightest regions , where the most massive stars reside 哈伯发现在星系中形成恒星的区域诞生超新星时，长时间的grb往往发生在非常明亮的区域，而质量最大的恒星也聚集在那里。
Besides acting as powerful signposts of active star formation , the intense maser emission provides a unique tool to probe the physical conditions and kinematics of these regions on scales of 10 - 103 au 星际脉泽不仅是恒星形成的一个及其重要的标志，而且也提供围绕大质量恒星尺度10 - 10 ~ 3au分子气体的物理条件和动力学结构的信息。
It says that the stars indeed rotate at different speed , but the density of the interstellar medium form a wave . at the wave front , where the density is higher , star formation is enhanced . that is why we find young stars along the spiral arms and old stars elsewhere 这个理论认为虽然恒星会以不同速度移动，但星际物质的密度会产生波动，在密度最高的波阵面会催生出新的恒星，这解释了为何通常在旋臂会找到新生恒星，而在其他地方只有古老恒星的原因。
To understand the connections between methanol masers and other phenomena typical of star formation region , such as the associated far - infrared sources , we have investigated statistical properties of all known 6 , 7 ghz methanol maser sources . the result suggests that 6 , 7 ghz methanol maser emission may appear only during a limited period of massive star formation 6 . 7ghz甲醇脉泽源的统计结果暗示着它们可能仅仅发生在大质量恒星形成的一个很短的时段内，可能起源于拱核盘中或外流中，远红外辐射则是一种可能的抽运机制。
The emerging consensus is that the early universe was dominated by a small number of giant galaxies containing colossal black holes and prodigious bursts of star formation , whereas the present universe has a more dispersed nature ? the creation of stars and the accretion of material into black holes are now occurring in a large number of medium - size and small galaxies 目前逐渐形成的共识是，早期宇宙是由数量稀少、但含有巨大黑洞，且恒星形成率超高的巨型星系所主宰，今日的宇宙则具有较零散的特性恒星的诞生与黑洞吸积物质的作用，发生在庞大数量的中、小型星系内。
To search for high - velocity molecular emission toward massive star formation regions , and to study the connections between h2o masers , iras objects and outflow properties , we carried out a co observation for a h2o maser sample . we found that most of the objects have excess high velocity emission produced by outflows ; we find a significant correlation between co line full widths and iras luminosities . the widths are proportional to the iras luminosities 通过在大质量恒星形成区搜寻高速分子辐射，并且研究它们与星际h _ 2o脉泽源和所联系的红外源之间的关系，我们发现绝大多数源都存在着气体的高速运动并且它们是由分子外流产生的；我们同时发现在co分子的谱线全宽和所对应源的红外光度之间存在很好的相关性，线宽随红外光度增加而变大。
