Photograph © Copyright Jenney Disimon
This week look westward in the early morning to see the daytime moon pale against the blue sky. It will appear higher and higher in the heavens as the week goes on.
The dichotomy of night and day, darkness and light, led many ancient cultures to worship the moon and sun together. But how is it we can sometimes see the brightest object in the night sky when the sun is beaming overhead? In simple terms, the moon is one of the few heavenly bodies whose light is bright enough to penetrate the scattered blue of the sky. However, it is only visible when high enough in
the heavens and when there is no cloud cover.
When the moon is full and at its brightest it sits directly opposite the sun in the sky, which means it is below the horizon while the sun is up. The new moon rises during the day, but sits too close to the sun to be seen. It sets at night, which is why the night sky is dark during the new moon. It is only in the days either side of full moon that conditions are ideal for it to be seen during the day.
In the days before full moon, look for the daytime moon in the afternoon skies; after full moon, look for it in the morning skies.
In some parts of the world the daytime moon is called the ‘children’s moon’. The phrase is reputed to stem either from the fact children rarely stay up late enough to see the moon in the night sky or because their eyesight is sufficiently sharp to spot it in the daytime, even when there is partial cloud cover.
OTHER CELESTIAL BODIES IN THE DAYTIME SKY
If you're looking at exactly the right spot with a telescope, you can see the planets Mercury, Venus, and Jupiter in daylight, along with one or two of the brightest stars, such as Sirius and Aldebaran.
Occasionally, other celestial objects can been seen in daytime with the naked eye. Venus is the most common, especially when it is near its greatest brilliancy, but as it appears as no more than a speck you do have to know exactly where to look against the ‘sea of blue sky’.
Brilliant meteors sometimes flare across the daytime sky. One such meteor blazed a path across America’s Grand Tetons in August 1972. More recently, a daylight meteor was reported over California and Nevada on 22 April 2012. Seen by thousands, it streaked across the sky creating a sonic boom that rattled windows. Astronomers said the meteor began as a small asteroid, the size of a mini-van.
Daytime comets are easier to spot than daytime meteors because they are more likely to be predicted ahead of their appearance. The Sutter’s Mill Comet in 2012, Comet McNaught in 2007 and a bright daytime comet preceding Halley’s comet in 1910 were all clearly visible to the naked eye. The Great Comets of 1843 and 1882 could be seen even when they were right next to the sun and were at least one hundred times brighter than the full moon. In fact, the 1882 comet was compared to the flame emitted by a smelting furnace.
Supernovae - massive stars or white dwarfs exploding at the end of their life cycles - have on rare occasions been visible during the day. Two famous examples are the Guest Star of Taurus in 1054 and Tycho’s Star of Cassiopeia in 1572. The most likely next candidate for a supernova
explosion visible during daytime is the star Betelgeuse.
Unquestionably, it will be visible in the daytime sky when it explodes, but when that will be is unknown. It could be tonight, or it could be tens of thousands of years from now.
There is an ancient and persistent belief (disputed by scientists) that it is possible to see some planets and stars in daylight from the bottom of a well or through a tall chimney. Aristotle mentioned this in one of his essays and Charles Dickens’s Pickwick Papers opens with it. According to lore, such a strictly narrowed field of vision serves to diminish the brightness of the daytime sky, making the ordinarily invisible stars starkly apparent.
By August 4, the moon will be at the last quarter phase – rising around midnight and southward around dawn. Then the moon will turn new on August 11, giving us deliciously dark skies for the upcoming Perseid meteor shower.
To learn more about moon phases and heavenly bodies in the daytime sky visit earthsky.org’s brilliant website.
Copyright © Karen Meadows 2018