Moon and Regulus

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Moon and Regulus

The Moon and the heart of the lion stand close together this evening. The lion’s heart is the star Regulus, to the lower right of the Moon at nightfall.

We see Regulus and the Moon for different reasons. Regulus is a star — a brilliant ball of hot gas. It generates its own light — so much light that it’s visible across almost 80 light-years. That means we see Regulus as it looked almost 80 years ago. So if anything big were to happen to the star tonight, Earth wouldn’t know it until early in the 22nd century.

The Moon doesn’t produce any light of its own. Instead, it reflects sunlight. The Moon looks big and bright only because it’s far closer to us than any other celestial object — an average of about a quarter of a million miles. That’s a bit more than one light-second, so we see the Moon as it looked a bit more than one second earlier.

Tonight, the Sun lights up a little more than half of the lunar hemisphere that faces our way. Many people think of that phase as a “half” Moon. And based on its appearance alone, that’s perfectly correct.

But a “half” Moon is also known as a quarter Moon. And at the current angle, it’s the first quarter Moon. That may sound confusing, but there’s a simple explanation: At first quarter, the Moon is one-fourth of the way through its month-long cycle of phases. It’s half of the way through the cycle when it’s full. And the cycle starts over at new Moon — when it’s not visible at all.

Script by Damond Benningfield

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