Astronomers have played many roles in their engagement with the larger astronomy education ecosystem. Their activities have served both the formal and informal education communities worldwide, with levels of involvement from the occasional participant to the full-time professional. We discuss these many diverse roles, giving background, context, and perspective on their value in encouraging and improving astronomy education. This review covers the large amounts of new research on best practices for diverse learning environments. This evidence-based perspective can support astronomers in contributing to the broad astronomy education ecosystem in more productive and efficient ways and in identifying new niches and approaches for developing the science capital necessary for a science literate society and for greater involvement of underrepresented groups in the science enterprise. Current research emphasizes the importance of ▪ The formation of science ideas in children and the development of their science identity ▪ The design of professional development programs for educators ▪ Museums and other informal learning institutions and settings ▪ The use of astronomical data and immersion experiences ▪ Shifting the astronomy education paradigm using new approaches with diverse audiences Expected final online publication date for the Annual Review of Astronomy, Volume 58 is August 18, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.