Amateur astronomer Juan Antonio Henriquez Santana took a look at Comet Holmes on Oct. 24, 2007, just after midnight, expecting to see the small comet tracing a relatively uninteresting path across the sky. Comet Holmes, a visitor to the inner solar system approximately every six years, should have sped past almost unnoticed by the planet below, visible only to those with reasonably large telescopes.
What Santana saw from his position in the Canary Islands was something quite different – a softly glowing ball. The comet swiftly brightened to become visible to the naked eye as a yellow star in the constellation Perseus. By the next day, it was one of the brightest stars in that constellation.
By mid-November, the comet’s nucleus – just 2.1 miles (3.4 km) in diameter, or the size of New York City’s Central Park, had exuded a coma bigger than the Sun. To put that in perspective, you could fit 1.3 million Earths inside the Sun. The dusty cloud around the comet’s nucleus was, for a time, the largest object in our solar system.
People were able to see the fuzzy, spherical, tail-less comet with the naked eye, even in large cities. In telescopes or binoculars, ...