Massive stars as cosmic engines

作为宇宙引擎的大质量恒星

• 批准号: 615-2006
• 负责人: Moffat, Anthony(Tony)
• 金额: $ 4.52万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=363154
• 关键词: Massive; stars; cosmic; engines

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.

作为宇宙引擎的大质量恒星由最初大于8个太阳质量的所有恒星组成，这些恒星在其核燃烧寿命结束时以超新星的形式坍塌，留下中子星或黑洞。由于一颗正常恒星的光输出为其质量的立方，所以一颗质量为100个太阳的恒星可以匹配一百万个太阳的总光。在20个太阳质量以上，大质量恒星通过它们的强风进一步区分自己，风速高达太阳的10亿倍。因此，尽管大质量恒星罕见且寿命短，但它们会释放大量辐射，主要是致命的紫外线，并向星际介质提供丰富的物质，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大。这个计划的主要目标是：(1)利用微型卫星上的第一个加拿大空间望远镜，探索(1)辐射压力本身是否可以驱动超新星前的极端风，燃烧氦的WR相，(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质，(3)风在明亮、炎热的恒星中扩展的确切方式，(4)磁场在加速风中的作用，(5)尘埃颗粒如何在炎热的发光恒星的恶劣环境中形成和生存的谜题，(6)最大质量恒星的质量上限(是100、150或200个太阳质量？)，(7)我们整个银河系中WR恒星的含量，大部分隐藏在星际尘埃中，以及(8)WR恒星是否真的以超新星的形式爆炸，在某些情况下导致了宇宙中最高能量(尽管短暂)的现象--长伽马射线爆发。