What is this holiday about?
To promote the science of Astronomy-
Astronomy Day is an annual event intended to provide a means of interaction between the general public and various astronomy enthusiasts, groups and professionals. The theme of Astronomy Day is "Bringing Astronomy to the People," but on occasion there is an additional theme (but not always) when conditions warrant. This additional theme is often decided just a few months prior to Astronomy Day.
Who celebrates this holiday? United National Observance
astroleague.org tells us that "Astronomy Day events take place at hundreds of sites across the United States. Internationally England, Canada, New Zealand, Finland, Sweden, the Philippines, Argentina, Malaysia, New Guinea plus many other countries have hosted Astronomy Day activities. Each location plans and executes events that work best for their local area." To locate the nearest event or to list your event see: http://www.astroleague.org/al/astroday/astroday.html
Origin of this holiday:This event was started in 1973 by Doug Berger, the president of the Astronomical Association of Northern California. His intent was to set up various telescopes in busy urban locations so that passersby could enjoys views of the heavens. Since then the event has expanded and is now sponsored by a number of organizations associated with astronomy.