LAST week’s relegation of the planet formerly known as Pluto – now classed merely as a dwarf planet – has upset some people. They had become rather attached to it. For 76 years, Pluto was one of only eight other worlds deemed worthy of being grouped in the same category as our own home. It was also the smallest planet by far – always an endearing characteristic, but also its problem, of course.
In recent years many other icy objects have been discovered out there beyond the orbit of Neptune, some of comparable size to Pluto, one of them bigger. If the word…
