While visiting Kentucky last week I spent a few hours with the knowledgeable and very gracious staff at the museum of the Kentucky Historical Center in Frankfort. While there I was pleased to see – and learn about – the orrery pictured above.

An orrery, I learned, is a mechanical model of the solar system. This one was made by Thomas Barlow – a mechanic and inventor who lived in Kentucky – and purchased in 1887 for use at a school in Lexington. It’s unknown how many orreries Barlow (and his son) made in their shop, but today there are only three intact models remaining around the world.