BETTII - the Balloon Experimental Twin Telescope for Far Infrared Interferometry

(根据提交的联合建议书-MJG_BETTII_PRD)自大爆炸以来，宇宙中产生的能量有一半以上现在以电磁辐射的形式存在于光谱的远红外部分--波长比可见光长几百倍。发育中的恒星和年轻恒星发出的大部分能量被形成它们的气体和尘埃云吸收，并在远红外中重新辐射。因此，如果我们想要了解今天我们银河系中恒星的诞生过程，或者研究星系是如何生长和发展的(通过恒星形成)，我们需要进行远红外观测。近年来，太空望远镜和高空气球上的操作取得了巨大的进步，我们努力了解恒星和行星系统形成的细节，以及像我们银河系这样的星系的历史。但是，远红外天文学在我们能够拍摄到与较短波长的光学望远镜和较长波长的射电望远镜阵列所获得的质量相似的照片之前，还有很长的路要走。由于大气在这部分光谱中被强烈吸收，因此必须从太空或从高空进行观测。这使得使用大型地面望远镜变得困难。此外，用于无线电领域的“干涉测量”技术，将许多较小望远镜的光束组合在一起，使图像与来自大得多的望远镜的图像一样好，但在远红外领域尚未完善。因此，目前，远红外观测的图像质量远远不能满足天文学家更好地了解恒星和星系及其起源的需要。在这个项目中，我们将取得重大进展，建立第一个工作在远红外的科学干涉仪，将它放在高空气球上，观测我们星系中的恒星形成区域和中心含有大质量黑洞的活动星系，以了解更多关于恒星如何形成星团以及黑洞如何与它们居住的星系相互作用的信息。就我们辨别图像细节的能力而言，这些开创性的测量将是最高质量的远红外观测服务器。除了给我们提供新的科学见解外，它们还将使我们能够完善和展示所需的技术，以在未来建立一个更雄心勃勃和更强大的仪器，也许是太空系统，以提供更好的观测。美国国家航空航天局和欧洲航天局都认识到了这种天文台的科学重要性，他们正在考虑这类太空任务。然而，目前还没有必要的技术和专业知识，这项工作将为建立我们执行这样一项任务的能力做出巨大贡献。

(as per submitted Joint proposal - MJG_BETTII_PRD)More than half of the energy generated in the Universe since the big bang now exists in the form of electromagneticradiation in the far infrared part of the spectrum - wavelengths a few hundred times longer than those of visible light. Muchof the energy emitted by developing stars and young stars is absorbed by the clouds of gas and dust in which they form,and re-radiated in the far infrared. So if we want to understand the birth processes of stars in our own galaxy today, or toinvestigate how galaxies grow and develop (through star-formation), we need to make observations in the far infrared. Inrecent years, huge advances have been made by telescopes in space and operating on high altitude balloons in ourendeavours to gain knowledge of the details of star and planetary system formation and the history of galaxies like our ownMilky Way. But astronomy at far infrared wavelengths has a long way to go before we will be able to take pictures withsimilar quality to that obtained by optical telescopes at shorter wavelengths and by arrays of radio telescopes at longerwavelengths.Observations have to be made from space or from high altitude because the atmosphere is strongly absorbing in this partof the spectrum. That makes it difficult to use large ground-based telescopes. In addition, the technique of "interferometry",used in the radio region of combining the beams from number of smaller telescopes to make an image as good as thatfrom a much larger one, has not yet been perfected in the far infrared. So at present, the image quality of observations inthe far infrared is not nearly as good as astronomers need to get a better view of stars and galaxies and their origins.In this project we will make a big advance by building the first scientific interferometer working in the far infrared, flying it ona high altitude balloon, and making observations of both of star forming regions in our galaxy and also of active galaxiesharbouring massive black holes at their centres, to learn more about how stars form in clusters and how black holesinteract with the galaxies they inhabit. These pioneering measurements will be the highest quality far infrared observationsever, in terms of our ability to discern fine details in the image. Besides giving us new scientific insights, they will allow usto perfect and demonstrate the technology needed to build a more ambitions and powerful instrument in the future, perhapsa space-borne system, to provide even better observations. The scientific importance of such an observatory has beenrecognised by both NASA and by the European Space Agency, who are considering space missions of this type. However,the necessary technology and expertise is not available yet, and this work will make a big contribution to establishing ourcapability to fly such a mission.