It’s likely that you know all this stuff already, so apologies for going over it again. These four planets were discovered between 1801 and 1807, lying in what we now consider to be the asteroid belt between Mars and Jupiter. They hung around in text books and the popular imagination as planets until, I gather, the 1850s, when they were demoted. I was thinking of this again this week because of the James Webb Telescope, which should hopefully be giving us its first pictures by the time you read this. This telescope will peer deeper into our universe than we’ve ever been able to look before. And along the way it will probably not just discover new stuff, but change the way we think about old stuff.
