Bill Bryson wrote, in 2003, “When I was a boy, the solar system was thought to contain thirty moons. The total now is “at least ninety,” about a third of which have been found in just the last ten years.”
Bryson was born in 1951 and therefore “a boy” would suggest the mid-1960s, more or less. The book, A Brief History Of Nearly Everything was a charming read but it itself is now over a decade old. If ~twenty moons were discovered in the 1990s alone, I suppose it’s not surprising to think that since 2003 that number has gone from “at least ninety” to 146. That’s not counting the 27 awaiting confirmation. In one decade we’ve discovered over 80 moons? Since Bryson’s boy years, we’ve found over 140!? There can be no doubt we’ve living through a wonderful age of space exploration.
As an armchair fan of astronomy, it’s remarkable to think we’ve done so much just in my lifetime alone. Voyager 2 visited Jupiter in 1979, Saturn in 1981, Uranus in 1986 and Neptune in 1989. With Pluto’s visit (regardless of its fair demotion to a dwarf planet), we’ve now images and data on the full Solar System I was taught about as a kid.
Not including dwarf-planet moons (at least 6), here’s the tally of known moons as of July 2015:
| Planet | # of Moons |
| Mercury | 0 |
| Venus | 0 |
| Earth | 1 |
| Mars | 2 |
| Jupiter | 50 (+17 awaiting confirmation) |
| Saturn | 53 (+9 awaiting confirmation) |
| Uranus | 27 |
| Neptune | 16 (+1 awaiting confirmation) |
Jupiter and Saturn each have more than double the moons as we knew existed in the Solar System just 50 years ago. I find this all marvelous and appreciate the fact that we are living through such a spectacular time of astronomical discovery. The sad truth lingers, however. This is the last of it all. No new planets (or dwarf planets) to visit. No new probes are being planned. I sincerely hope the James Webb Space Telescope lives up to its promise (and everything goes without a hitch). The scope of that promise is only matched by its potential for failure. Not to be a downer or anything…
[Moon info from NASA]
[Humbling astronomy video just because]