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Even under the most ideal conditions, we can never see Mercury more than 28 degrees from the sun, which means it can never appear in a completely dark sky. (Illustration by Creators.com)
In Roman times he was known as the god of trade, travel and theft. The Greeks called him Hermes, the messenger of the gods, when he appeared at sunset, and they called him Apollo when they saw him at dawn.
Today we know it as Mercury – the planet closest to the sun – and this elusive planet returned to our sky at dawn this week for all to enjoy.
I call Mercury “elusive” because it revolves around the sun in just 88 days and, as a result, never stays in our sky for long and never moves away from the sun’s glare. Even under the most ideal conditions, we can never see Mercury more than 28 degrees from the sun, which means it can never appear in a completely dark sky.
This week, however, you can find the planet as long as clear weather stretches to the eastern horizon during the morning twilight.
In what many believe to be an ungodly hour, you’ll have little trouble seeing the dazzling Venus, easily the brightest object in the dawn sky.
Below and to the left of it, you may notice that Mercury appears as a fainter yellowish “star”. If you notice this, you should consider yourself lucky; it has been said that the great 16th-century Polish astronomer Nicolaus Copernicus – who calculated the movements of the planets – had never seen this world with his own eyes.
Don’t be surprised if Mercury seems to glow; the thick column of air through which its light must pass will also do so to a planet, despite what we may have learned in school.
If you have a small telescope, point it at each of these distant worlds. The moon, of course, will be extraordinarily beautiful; the planets, however, will show little more than you can see with the naked eye. This is because Venus is shrouded in clouds and Mercury’s light passes through so much swirling air near our horizon that its details are nearly impossible to discern.
However, before putting the telescope away, try a slightly higher magnification eyepiece. You may notice that Venus is not perfectly round; it appears this week in a “gibbous” phase, just as our moon does just before or after it is full. This will, of course, change as Venus orbits the sun later this fall and winter.
Point towards Mercury now, but don’t be surprised how small it remains and how blurry it becomes. First of all, this planet is barely the size of the continental United States. Second, the extra power amplifies not only the planet, but also the air turbulence and heat currents that rise from our earth’s landscape.
If you are lucky enough to see a relatively stable image, you may notice that Mercury now displays a near “quarter” phase, but for this you will need a fairly stable atmosphere and a more powerful eyepiece.
Keep an eye out for Mercury for the next few mornings as its relatively rapid orbit around the sun will cause its appearance to change to an almost “full” phase before it disappears from our sky once again.
The waning crescent moon will appear to pass just above Venus on November 12 and above Mercury on November 13.
– Dennis Mammana is an astronomy writer, author, lecturer, and photographer working under the clear, dark skies of the Anza-Borrego Desert, inland from San Diego County. Contact him at [email protected] and connect with him on Facebook: @dennismammana. Click here to read the previous columns. The views expressed are his.
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