Sounding the Stars: OCTAVE, the Birmingham Seismology Programme

探寻星空：OCTAVE，伯明翰地震学计划

• 批准号: ST/H001875/1
• 负责人: Yvonne Elsworth
• 金额: $ 71.58万
• 依托单位: University of Birmingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FH001875%2F1
• 关键词: Sounding; Stars; OCTAVE; Birmingham; Seismology

Stars are the visible building-blocks of the Universe and the nearest star to us, the Sun, is vital to life on Earth. Our research aims to 'look' deep inside the Sun and stars to help us understand how they work and evolve. Although you can't see it without special equipment, the Sun is shaking, and many stars are too. Bubbling motion just under the visible surface of the star constantly feeds in energy, and the star responds by vibrating like a (very) large musical instrument. The 'notes' of the stars are very interesting to astronomers. They are produced by sound waves which have travelled deep inside and their frequencies (the 'pitches' of the notes) depend on the conditions they meet on the way, such as the density and temperature of stellar material. By studying them astronomers essentially get an 'ultrasound scan' of a star - we can understand better everything from what makes the vibrations in the first place, all the way to the nuclear reactor at the star's core. By studying the Sun we examine one star in exquisite detail, whilst gaining information on a range of stars allows us to test our models of stars with different masses, compositions and ages. We can then study how stars like the Sun evolve - we can see the future of the Sun Turning these ideas into scientific reality is very difficult. The shaking is very small - the surface moves to and fro at a couple of metres per second (in the solar case) and cycles in about 5 minutes. Just detecting the small movements takes specially designed instruments (called spectrometers, because they examine a star's spectrum). At the same time the star's brightness changes by about 1 part in 10,000, just detectable from Earth for the Sun, but too subtle to be measured in other stars through the Earth's atmosphere. Some interesting effects on stars can last for several years. For example, we know that stars have cycles of magnetic activity which we don't fully understand yet - the Sun's has periods of 'spottiness' every 11 years or so. For this and other reasons, you would really like to observe the stars' vibrations continuously for many years. One way is to put a number of robotic spectrometers in different places around the world, so that when a star sets on one instrument it has already risen on another. We have been doing this for the Sun for about 30 years, by operating the Birmingham Solar Oscillations Network (BiSON), and now aim to use this expertise in the development of a network for studying stars. Colleagues in Denmark are designing the prototype instrument for SONG (the Stellar Oscillations Network Group). We aim to contribute to instrument design and control to help SONG develop, as well as continuing our solar observations. Another way to study the oscillations of stars is to observe their small brightness fluctuations from space, and a number of current satellites can do this. Techniques we have developed for studying the Sun are transferrable to other stars and the satellite data. We have been working in recent years with international colleagues to prepare for data that the NASA satellite, Kepler, will produce (from the middle of 2009) and we aim to work on hundreds of stars in the coming years. We will also use data from the SMEI satellite to study the rather different pulsations of O and B stars, which are much hotter than the Sun. Here the pulsations are so dramatic that they may play a part in the stars losing mass from their outer layers - our work will help to examine this mass loss. So our new proposal is to extend our observational and analytical experience from our solar work to other stars and to continue to operate the BiSON network, collecting high quality solar data. We will use stellar and solar data to provide new information on the deep interiors of stars (especially to study stellar evolution) and to improve our understanding of stellar activity cycles and of the outer convective layers of stars where the vibrations are generated.

恒星是宇宙的可见组成部分，距离我们最近的恒星太阳对地球上的生命至关重要。我们的研究旨在“观察”太阳和恒星的深处，以帮助我们了解它们是如何工作和演化的。虽然没有特殊设备你看不到它，但太阳在晃动，许多星星也在晃动。恒星可见表面下的气泡运动不断地提供能量，恒星通过像一个（非常）大的乐器一样振动来做出反应。天文学家对恒星的“笔记”非常感兴趣。它们是由深入内部的声波产生的，它们的频率（音符的“音调”）取决于它们在途中遇到的条件，例如恒星物质的密度和温度。通过研究它们，天文学家基本上可以对恒星进行“超声波扫描”——我们可以更好地了解一切，从最初产生振动的原因，一直到恒星核心的核反应堆。通过研究太阳，我们可以详细地检查一颗恒星，同时获得一系列恒星的信息，使我们能够测试具有不同质量、成分和年龄的恒星模型。然后我们可以研究像太阳这样的恒星如何演化——我们可以看到太阳的未来将这些想法变成科学现实是非常困难的。晃动非常小——表面以每秒几米的速度来回移动（在太阳能情况下），循环周期约为 5 分钟。仅仅检测微小的运动就需要专门设计的仪器（称为光谱仪，因为它们检查恒星的光谱）。与此同时，恒星的亮度变化约为万分之一，从地球上的太阳只能检测到，但在其他恒星中通过地球大气层无法测量到。对恒星的一些有趣影响可以持续数年。例如，我们知道恒星具有我们尚未完全了解的磁活动周期——太阳每 11 年左右就会出现一次“斑点”周期。由于这个和其他原因，你真的很想连续多年观察恒星的振动。一种方法是将许多机器人光谱仪放置在世界各地的不同地方，这样当一颗恒星在一台仪器上落下时，它就已经在另一台仪器上升起了。我们通过运营伯明翰太阳振荡网络 (BiSON) 为太阳做这件事已经有大约 30 年了，现在的目标是利用这些专业知识来开发一个用于研究恒星的网络。丹麦的同事正在为 SONG（恒星振荡网络小组）设计原型仪器。我们的目标是为仪器设计和控制做出贡献，以帮助 SONG 发展，并继续我们的太阳观测。研究恒星振荡的另一种方法是从太空观察它们微小的亮度波动，目前的许多卫星都可以做到这一点。我们开发的用于研究太阳的技术可以转移到其他恒星和卫星数据上。近年来，我们一直在与国际同事合作，准备 NASA 卫星开普勒（从 2009 年中期开始）将产生的数据，我们的目标是在未来几年对数百颗恒星进行研究。我们还将利用 SMEI 卫星的数据来研究 O 星和 B 星截然不同的脉动，它们比太阳热得多。这里的脉动是如此剧烈，以至于它们可能在恒星外层质量损失中发挥了作用——我们的工作将有助于检查这种质量损失。因此，我们的新建议是将我们的太阳工作中的观测和分析经验扩展到其他恒星，并继续运营 BiSON 网络，收集高质量的太阳数据。我们将利用恒星和太阳数据提供有关恒星内部深处的新信息（特别是研究恒星演化），并提高我们对恒星活动周期和产生振动的恒星外对流层的理解。