Open astronomy book

An idea, and a question (or the other way around). I’ve always liked astronomy; growing up I had several astronomy books and a small telescope, I eagerly consumed news and information about space (I had a newspaper photo clipping of Saturn as taken from Voyager taped to my wall), and I took Astronomy for my physics elective in college, and one thing that always struck me was how outdated the various books I had were, even though they were relatively new (at the time I got them). You would read some theoretical composition of Jupiter’s atmosphere even as data was coming in updating and contradicting the old information.

So I was thinking the other day of the planet Pluto and how it has three moons now (I don’t remember the context), and how this information could potentially change some fundamental conception of the solar system, and yet it would probably take a year, maybe 18 months before this would make it into the latest and greatest book on astronomy. And I thought, wouldn’t it be neat if there was an open (as in open source) astronomy book online somewhere, maybe like a wiki, that was textbook-quality and was kept up-to-date with the latest discoveries? People could freely access it, print it out, download a copy, whatever, and it would always be relevant.

The question: Does such a thing exist already? Now, I’m familiar with Wikibooks, the self-described “open-content textbooks collection,” but their Astronomy book is paltry at best. (It might make a good starting point, though.) So does anyone know of something like this?

If not, I might start it myself. It would make a neat hobby, at the very least.

(And if it worked, this would make a good model for other books that could be open and possibly wiki-fied. I’ve got a few ideas.)