Massive stars as cosmic engines

大质量恒星是宇宙引擎大质量恒星包括所有最初质量超过8个太阳质量的恒星，它们在核燃烧生命结束时坍缩为超新星，留下中子星或黑洞。由于一颗普通恒星的光输出是其质量的立方，一颗100太阳质量的恒星可以与100万个太阳的总光相匹配。质量超过20个太阳质量的大质量恒星通过其强风进一步区分自己，强风的强度可达太阳的10亿倍。因此，尽管罕见且寿命短暂，但大质量恒星会向星际介质释放大量辐射（主要是致命的紫外线）和富集物质，准备建造更多的恒星和像地球这样的行星。这在宇宙早期尤为重要，因为最初形成的恒星可能都非常巨大。本课程的主要目标是探讨：(1)如果单靠辐射压力就能驱动超新星爆发前的极端风，即氦燃烧的WR阶段，使用加拿大微型卫星MOST上的第一台太空望远镜；(2)建造一颗纳米卫星，系统地探测大量明亮大质量恒星的低振幅不稳定性；(3)风在明亮热恒星中膨胀的确切方式；(4)磁场在加速风中的作用；(5)尘埃颗粒如何在炎热明亮的恒星的恶劣环境中形成和生存的谜题；(6)最大质量恒星的最高质量界限（是100、150还是200个太阳质量？）；(7)我们整个银河系中大部分被星际尘埃隐藏的WR恒星的含量；(8)WR恒星是否真的会爆炸成超新星，在某些情况下导致宇宙中最具能量（尽管寿命很短）的现象，即长伽马射线暴。

MASSIVE STARS AS COSMIC ENGINES Massive stars comprise all stars initially above 8 solar masses, that collapse as supernovae at the end of their nuclear-burning lives, leaving behind neutron stars or black holes. Since the light output of a normal star goes as the cube of its mass, a single, 100 solar-mass star can match the total light from a million Suns. Above 20 solar masses, 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 radiation, mostly as lethal ultraviolet, 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. The main goals of this program are to explore: (1) if radiation pressure alone can drive the extreme winds of the pre-supernova, He-burning WR phase, using the first Canadian space telescope on board the microsatellite MOST, (2) building a nanosatellite to systematically probe the low-amplitude instability properties of a large number of bright, massive stars, (3) the exact way in which the winds expand in luminous, hot stars, (4) the role of magnetic fields in accelerating the winds, (5) the puzzle of how dust grains form and survive in the hostile environments of hot, luminous stars, (6) the upper mass cut-off for the most massive stars (is it 100, 150, or 200 solar masses?), (7) the content of WR stars in our whole Galaxy, mostly hidden by interstellar dust, and (8) whether WR stars actually explode as supernovae, leading in some cases to the most energetic (although short-lived) phenomenon in the Universe, the long gamma-ray bursts.