Stargazing: New moon provides best time for stargazing


Wednesday is the first new moon after the August 21 eclipse of the sun. Solar eclipses happen when the moon passes in front of the sun, which means that only the part of the moon invisible to us is illuminated. The dark side of the moon is thus presented to us during an eclipse. That moon is traditionally called the new moon even though it is a night of no moon at all.

Of course, a new moon happens once every lunar cycle — once a “moonth,” one might say. Where do you think the word “month” comes from?

However, observers on Earth do not get a solar eclipse every new moon. The orbits of Earth around the sun and the moon around the Earth are tilted with respect to each other. It is a rare event indeed when the orbits cross.

Thus, most people have never greeted the new moon with much enthusiasm. However, in the days before streetlights, many a lover has waxed poetic about the full moon. Many a lover’s liaison was lit by “the light of the silvery moon,” as the old song goes.

A night with no moon means that such activities must wait. Who wants to go stumbling out in the dark? As the 9th-century Japanese poet Ono no Komachi writes,

The night of no moon,

There is no way to meet him

I rise in longing

My breast pounds, a leaping flame,

My heart is consumed by fire.

And then there are the crusty old curmudgeons like me who are consumed by a different kind of fire. They love those nights when the moon does not shine in the sky.

Those “deep-sky observers,” as they are called, must watch the phases of the moon very carefully because its harsh brightness washes out the subtle light of emission nebulae, where stars are born and die, and distant galaxies of stars.

In fact, as long as we have walked on the planet, humans have noticed that the moon follows a predictable path across the sky. And we noticed that the moon has phases over about a 29-day cycle.

The cycle begins with the “new moon,” which is one phase that amateur astronomers don’t mind. On that night, we see only the unilluminated face of the moon, which rises around sunrise and sets with the sun, so we don’t see it at night.

No moon means that the light from stars is uninterrupted. It’s the best time for gazing at the stars.

During the week after new moon, the moon is up in the early evening sky and sets a bit later each night.

At the end of the week, we see a half moon, called the “first-quarter.” It doesn’t set until the night is half over and looks like at half-eaten pizza from the Chernobyl Pizza Co. Deep-sky observers must wait impatiently until the moon sets, and that makes for bleary-eyed activities the next day.

The next phase is miserable indeed. The moon is up in the early evening and stays in the night sky, growing fatter and fatter. During this “gibbous” phase, stargazers stay home and polish their telescopes.

At the end of the week, the moon reaches its full, or “second-quarter” phase.

The night of the full moon is great for courtship but lousy for stargazing. The moon rises around sunset and sets around sunrise.

By about a week later, the moon has shrunk again to half its size. The “third-quarter” moon doesn’t rise until the night is half over, so you can get in a little early evening observing.

Over the next week, the moon continues to shrink to a smaller and smaller crescent and rises later and later. On the night of the “new moon,” it again disappears from the night.

The moon does not shine with its own light; it reflects the light of the sun. We see different phases of the moon because we view its illuminated face from different angles as it orbits Earth.

That’s the scientific explanation, but science can be terribly unpoetic.

In the past, most people saw the moon as a goddess whose light brought fertility to the world. She made the crops grow, and her light brought beauty to the faces of women who bathed in her brilliance.

Hindu women laid a bowl of milk under the light of the full moon. It was said that bathing in that milk would keep them eternally beautiful, and drinking the milk would make them capable of bearing many children.

Some island people of Oceana believed that the phases of the moon reflected the cycle of pregnancy and birth. As the moon grew larger, her child grew within her. At the full moon, she was ready to give birth. She then entered a protracted 14-day labor, at the end of which she always died. For a day, no moon lit the sky, and people mourned her death. But the next day, or the day after, her child appeared in the sky as a thin crescent, and the cycle began anew.

If cosmic ardor burns in your heart, I hope you’ll go out and observe the baby moon two days after the new moon.

This month, the new moon, the night when the moon lies hidden, is Wednesday September 20. Two days later, on the night of September 22, you can observe the beautiful, shard-like sliver of the two-day-old moon. Look low in the eastern sky at the place where the sun has just set. As twilight darkens to night, you might be able to glimpse the baby.

It will look, as Chet Raymo writes in The Soul of the Night, “crooked like Cupid’s bow, its arrow aimed at the sun.”

So go out and look if the sky is clear. After all, a lovely, ancient goddess has destroyed herself to give birth to this newborn splendor. Let us not fail to note her passing and revel in the new life.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.