Moon and Spica

StarDate

The Moon gets especially cozy with the star Spica this evening. From much of the United States, in fact, the Moon will pass in front of the bright star, blocking it from view for a while. Astronomers will keep an eye on the event – called an occultation – to learn more about Spica.

In earlier days, occultations also helped scientists map the Moon. The way a star disappeared and reappeared could reveal the contours of lunar mountains, valleys, and craters. We still see those features during occultations, but they’ve been well mapped.

Scientists have been making maps of the Moon for centuries. Perhaps the earliest known map – a truly accurate chart of lunar features – was created by William Gilbert, a British scientist and a physician to Queen Elizabeth I. He drew it no later than 1603, before the invention of the telescope, using his eyes alone. But it wasn’t published until 1651.

By then, Polish astronomer Johannes Hevelius had published a whole atlas of the Moon, made with a telescope. He named many of the lunar features. Eventually, though, the names were superseded by those created just a few years later by Giovanni Riccioli, a scientist and Jesuit priest. And most of his names are still in use today.

Many more names have been added in recent decades, thanks to the detailed pictures taken by orbiting spacecraft. All of those names are found on modern maps of the Moon.

Script by Damond Benningfield