BETTII - the Balloon Experimental Twin Telescope for Far Infrared Interferometry

(as根据提交的联合提案- MJG_BETTII_PRD）自大爆炸以来，宇宙中产生的能量中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。发展中的恒星和年轻恒星释放出的大部分能量被它们形成的气体和尘埃云吸收，并在远红外线中重新辐射。因此，如果我们想了解我们银河系中恒星的诞生过程，或者研究星系如何成长和发展（通过恒星形成），我们需要在远红外线上进行观测。近年来，太空望远镜和高空气球的使用取得了巨大的进步，我们努力获得关于星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的知识。但是远红外波段的天文学还有很长的路要走，我们才能拍摄到与光学望远镜在较短波长和射电望远镜阵列在较长波长所获得的图像质量相似的图像。观测必须从太空或高空进行，因为大气对这部分光谱有很强的吸收。这使得使用大型地面望远镜变得困难。此外，在无线电领域使用的“干涉测量”技术，即把来自许多小望远镜的光束结合起来，使图像与来自大得多的望远镜的图像一样好，在远红外线方面还没有完善。因此，目前，远红外线观测的图像质量远不如天文学家所需要的那样好，天文学家需要更好地观察恒星和星系及其起源。在这个项目中，我们将通过建造第一个在远红外线下工作的科学干涉仪，将其放在高空气球上，并对银河系中的星星形成区和中心有大质量黑洞的活跃星系进行观测，来了解更多关于恒星如何在星团中形成以及黑洞如何与它们所居住的星系相互作用的信息。这些开创性的测量将是最高质量的远红外观测服务器，就我们辨别图像细节的能力而言。除了给我们带来新的科学见解，它们还将使我们能够完善和展示所需的技术，以便在未来建造一个更有雄心和更强大的仪器，也许是太空系统，以提供更好的观测。这样一个天文台的科学重要性已经被美国宇航局和欧洲航天局认识到，他们正在考虑这种类型的太空任务。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使命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.