Astronomy is the study of the objects, the material, and the processes that occur in distant space. The domain of astronomy consists of all that lies outside the Earth’s atmosphere. Over the last few decades a wealth of data have been collected on our solar-system neighbours from the Moon and Mars to Trans-Neptunian Objects, and their study has emerged as a distinct discipline. It is sometimes convenient to think of astronomical space as that which lies outside the heliosphere.
The processes that operate in the vast expanses of the universe are governed by the same physical laws that apply on earth. As a metaphysical hypothesis, this idea (or its exact opposite as in Aristotle’s sublunary sphere) can possibly be traced back to antiquity in many cultures. The central contribution of the experimental and mathematical sciences developed through and beyond the European Renaissance of the 14th-17th centuries to astronomy was to provide the intellectual tools whereby observations of remote objects could be used to establish that the terrestrial laws of physics were applicable in distant space. By the middle of the 19th century, when the dispersive spectroscope was incorporated into astronomical observations, the cosmic applicability of physical laws had long been accepted as a core principle by the scientific community.
Astronomers do not have control over the objects of observation. Instead, different and better instruments and detectors need to be designed and built so that a broader range of phenomena can be observed, and measurements made with greater precision. Thus, modern astronomy and technological innovation are closely linked. The linkages are not restricted to telescopes and detectors, but include also observatories (ground and space-based) and their peripheral systems, and the infrastructure (hardware and software) for handling large volumes of data.
Representations of data and their interpretation, and recently, of the results of computer simulations are important in astronomy. Images, spectra, and relational plots are the three most common representations used in publications. Images may be derived directly from data, or they may be schematic drawings, or more elaborate artistic impressions. Spectra are typically plots of flux against wavelength (or a related quantity such as frequency). Combinations or sequences of images are used for representing data-cubes where two dimensions correspond to directions in the plane of the sky, and the third is wavelength (or frequency) that can be reliably interpreted as a Doppler-shifted velocity. Relational plots come in many forms; the most famous of these may be the Hertzsprung-Russell diagram that locates each star via its magnitude and color, or with a theoretically derived luminosity and effective temperature. A number of choices need to be made while designing a representation, and the aesthetics of visualization determines the effectiveness of the representation in conveying the fundamental astronomical result.
The many facets of astronomy – the sense of exploration, the link to basic physical laws, the connection to techne, and the requirement of aesthetic expression – make it a compelling vocation for its practitioners. Uniting these elements, and by giving us knowledge of distant space, Astronomy provides the backdrop and inspiration for grand narratives, which carry within them the essence of the truth about our human societies and civilization.