Is it bigger than a breadbox? Probing stellar secrets by modelling spectra of magnetic and other stars

天空中最明显的天文天体，我们的太阳，是一颗典型的恒星。在晚上，我们在天空中看到的大多数是其他恒星，它们与太阳非常相似，只是它们有各种各样的大小、表面温度、距离等。在过去一个世纪的大部分时间里，许多天文学家一直在积极尝试获取关于单个恒星的信息(例如每颗恒星有多少质量)，以了解恒星在发光表面下是什么样子(内部有多热和多密集？这种物质是气态的吗？)，特别是为了了解恒星是如何形成和变化的，并最终坍塌成巨大的炽热的煤渣。 了解恒星需要我们从它们向我们发出的微弱光线中尽可能多地获取信息。这道光包含了惊人的信息量。通过详细研究光，我们经常可以发现恒星有多大，有多热，有多远，有多大质量。我们还可以获得更详细的表面层(恒星的“大气”)的信息，例如气体的密度有多大，气体的化学成分是什么，气体是安静的还是像刮风的日子一样冒泡和吹。 我的整个研究计划集中在利用星光来尝试回答关于特定类型恒星的特定问题。例如，观察到一些恒星受到强磁场的渗透。我正在观察一些恒星的磁场，这些恒星所处的环境允许我们估计它们的年龄，并寻找这些恒星的平均磁性如何随着年龄的变化而变化的证据，从年轻的恒星到年长的恒星。回答这个问题应该有助于我们理解恒星中的磁场是如何增长和变化的。 我的计划的另一个方面是在白矮星中寻找非常弱的磁性。当像太阳这样的恒星耗尽燃料并塌缩成“微小的”天体时，这些炽热的恒星身体就会产生，这些天体大约和地球一样大，经过多年的冷却。这也应该有助于我们更好地理解恒星中的磁场。 我也在观察恒星发出的光，这些恒星非常年轻，它们周围仍然有一些气体，这些气体是重力聚集在一起形成新恒星的。靠近恒星但尚未落到表面的气体被来自新恒星的光加热，并发光。可以对这种发光进行分析，以找到关于这种气体的更多信息--那里有多少物质，它有多热，等等。 我的研究中的每一个方面都深入探讨了一个关于恒星的非常小的、具体的问题，但结果就像一块巨大的拼图--把它们放在一起，可以让我们更好地理解恒星如何形成和改变他们生活的大故事。

The most obvious astronomical object in the sky, our Sun, is a typical star. At night most of what we see in the sky is other stars, bodies much like our Sun except that they come in a wide variety of sizes, surface temperatures, distance, etc. For much of the past century, many astronomers have been actively trying to obtain information about individual stars (such as how much mass each has), to understand what stars are like below their glowing surfaces (How hot and how dense is the interior? Is the material gaseous?), and particularly to understand how stars form and change, and eventually collapse to huge hot cinders. Learning about stars requires us to squeeze as much information as possible from the faint light they send to us. This light contains an astonishing amount of information. By studying the light in detail, we can often discover how large the star is, how hot, how far away, and how massive. We can also get more detailed information about the surface layer (the star's "atmosphere''), for example how dense the gas is, what the chemical composition of the gas is, and whether the gas is quiet or is bubbling and blowing like a windy day. My overall research programme focusses on using starlight to try to answer specific questions about specific kinds of stars. For example, some stars are observed to be permeated by strong magnetic fields. I am looking at the fields of a number of stars that are in environments which allow us to estimate their ages, and searching for evidence of how the average magnetism of these stars changes with age, from young stars to older ones. Answering this question should help us to understand how magnetic fields grow and change in stars. Another aspect of my programme involves looking for very weak magnetism in white dwarf stars. These are the hot stellar corpses that result when a star like the Sun runs out of fuel and collapses to become a "tiny'' body, about as large as the earth, that simply cools through the ages. Again this should help us to understand magnetic fields in stars better. I am also looking at the light from stars that are so young that they still have around them some of the gas that gravity pulled together to form the new star. The gas that is close to the star but has not yet fallen onto the surface is heated by the light from the new star, and glows. This glow can be analysed to find out more about that gas - how much material is there, how hot it is, and so on. Each of these aspects of my research digs into a very small, specific question about stars, but the results are like pieces of a huge jigsaw puzzle - putting them all together allows us to understand better the big story of how stars form and change through their lives.