For millennia, the awe and wonder of the night sky has captivated and inspired humans to explore some of the most fundamental mysteries of the Cosmos through different perspectives and disciplines. Astronomy as a field of inquiry exemplifies a synergy of disciplines, a synergy that is more often tacit. Over the years, education and educational reforms have evolved into creating demarcated subjects. While this is understandable from a technical perspective, it delimits and misrepresents the breadth of research contributing to the field and its wider implications. This applies to ways that astronomy relates to the STEM disciplines, but more widely to art and science interactions. One of the unfortunate implications of this is that students are not able to fully appreciate the fact that exploration, solving problems and development of astronomical knowledge require the synergetic interaction between knowledge and skills from a range of disciplines. In order to highlight the potential for interdisciplinary synergies, this paper explores one of the most ancient of disciplinary synergies, that of art and science, in the context of astronomy. Through the analysis of various astronomical art-science projects, the aim is to theoretically characterise this synergy through the lens of social semiotics and its associated constructs. The proposed theoretical characterisation is used to provide examples of how this synergy can be productively realised in the context of the classroom.