BETTII - the Balloon Experimental Twin Telescope for Far Infrared Interferometry

自大爆炸以来，宇宙中产生的能量有一半以上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发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，在我们努力了解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方面，空间望远镜和高空气球望远镜取得了巨大进展。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获得的图像质量相似的图像。必须从太空或高空进行观测，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，即把来自许多较小望远镜的光束结合起来，使图像与来自一个大得多的望远镜的图像一样好，在远红外方面还没有完善。因此，目前，远红外观测的图像质量远不如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，在高空气球上飞行，并对我们银河系中的星星形成区域以及中心有大质量黑洞的活动星系进行观测，以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有史以来最高质量的远红外观测，就我们辨别图像中细节的能力而言。除了为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未来建造更雄心勃勃和强大的仪器所需的技术，也许是一个空间系统，以提供更好的观测。这样一个天文台的科学重要性已经得到美国航天局和欧洲航天局的认可，他们正在考虑这类空间任务。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很大贡献。

More than half of the energy generated in the Universe since the big bang now exists in the form of electromagnetic radiation in the far infrared part of the spectrum - wavelengths a few hundred times longer than those of visible light. Much of 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 to investigate how galaxies grow and develop (through star-formation), we need to make observations in the far infrared. In recent years, huge advances have been made by telescopes in space and operating on high altitude balloons in our endeavours to gain knowledge of the details of star and planetary system formation and the history of galaxies like our own Milky Way. But astronomy at far infrared wavelengths has a long way to go before we will be able to take pictures with similar quality to that obtained by optical telescopes at shorter wavelengths and by arrays of radio telescopes at longer wavelengths.Observations have to be made from space or from high altitude because the atmosphere is strongly absorbing in this part of 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 that from a much larger one, has not yet been perfected in the far infrared. So at present, the image quality of observations in the 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 on a high altitude balloon, and making observations of both of star forming regions in our galaxy and also of active galaxies harbouring massive black holes at their centres, to learn more about how stars form in clusters and how black holes interact with the galaxies they inhabit. These pioneering measurements will be the highest quality far infrared observations ever, in terms of our ability to discern fine details in the image. Besides giving us new scientific insights, they will allow us to perfect and demonstrate the technology needed to build a more ambitions and powerful instrument in the future, perhaps a space-borne system, to provide even better observations. The scientific importance of such an observatory has been recognised 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 our capability to fly such a mission.