Massive stars as cosmic engines

大质量恒星包括所有初始质量超过8个太阳质量（Msun）的恒星。直到大约100兆太阳的时候，它们在连续的、越来越热的中心壳层中燃烧元素，直到铁，然后变成核心坍缩的超新星，根据初始质量留下中子星星或黑洞残余。 超过100 Msun时，它们只会在核心燃烧成氧气，然后变成完全分裂的对不稳定超新星。由于一颗正常星星的辐射输出大约是其质量的立方，因此一颗100兆太阳的星星相当于一百万个太阳的总辐射输出。 在大约20 Msun以上，大质量恒星通过它们的强风进一步区分自己，范围高达太阳的十亿倍。 因此，虽然稀有且寿命短暂，但大质量恒星向星际介质提供大量致命的紫外线辐射和浓缩物质，准备建造更多像地球一样的恒星和行星。 这在早期宇宙中尤其重要，当时形成的第一批恒星可能都非常巨大。显然，大质量恒星主宰着宇宙的生态，但它们的许多基本参数仍然难以捉摸。 该计划的主要目标是探索：（A）大质量恒星中的脉动，这可以提供额外的能量来驱动风，并将为大质量恒星的内部结构提供重要而紧迫的线索（利用MOST微型卫星上的加拿大第一台空间望远镜，以及下一个项目：超小型卫星BRITE-星座）;（B）恒星风的性质，这在大质量恒星中占主导地位;（C）尘埃颗粒如何形成并在某些炽热发光恒星的恶劣环境中生存的神秘过程;（D）星星形成的质量上限以及恒星最终成为白色矮星、中子星或黑洞的边界;（E）我们银河系中WR星的含量（迄今为止大多被星际吸收所隐藏）和许多其他附近的恒星形成星系（作为最佳候选者，是Ib和Ic型超新星的直接前体）。

Massive stars comprise all stars initially above 8 solar masses (Msun). Up to about 100 Msun they burn elements in successive, ever-hotter central shells right through to iron, before becoming core-collapse supernovae, leaving a neutron star or black hole remnant depending on the initial mass. Above about 100 Msun they burn only to oxygen in their cores before becoming pair-instability supernovae with complete disruption. Since the radiative output of a normal star goes roughly as the cube of its mass, a single 100 Msun star matches the total radiation output from a million Suns. Above some 20 Msun, massive stars further distinguish themselves by their strong winds, ranging up to a billion times that of the Sun. Thus, although rare and short-lived, massive stars deliver huge quantities of mostly lethal UV radiation and enriched material to the interstellar medium, ready to build more stars and planets like Earth. This was especially important in the early Universe, when the first stars formed were probably all very massive. Clearly, massive stars dominate the ecology of the Cosmos, yet many of their basic parameters remain elusive. The main goals of this program are to explore: (A) pulsations in massive stars, which could provide additional energy to drive the winds and which will provide important and urgent clues to the internal structure of massive stars (using Canada's first space telescope aboard the MOST microsatellite, and the next venture: the nanosatellite BRITE-Constellation); (B) the nature of stellar winds, which dominate in massive stars; (C) the mysterious process of how dust grains form and survive in the hostile environments of some hot, luminous stars; (D) the upper mass limit of star formation and the boundaries between which stars end up as white dwarfs, neutron stars or black holes; (E) the content of WR stars in our own Galaxy (heretofore mostly hidden by interstellar absorption) and in many other nearby star-forming galaxies (as best-candidate, immediate precursors to supernovae of type Ib and Ic).