Don’t miss rare chance to see Mercury

By Tom Burns - Stargazing

Starting this evening and continuing for a week or so, stargazers get our best chance to see the elusive planet Mercury this year.

Take every clear-sky opportunity you can. Clear nights have been relatively rare these days.

We can only see planets when the sun is below the horizon or just setting because the sun’s glare washes out the sky. Exceptions are the moon and Venus, which sometimes can be seen in daylight.

The trouble with Mercury is that it’s so darn close to the sun at an average distance of only 36 million miles compared with Earth’s 93 million miles.

As a result, Mercury spends most of its time behind or too close to the sun for us to see. We can only see it just before the sun rises or just after it sets, and only when it is as far from the sun from our point of view as it can get.

This time around, you’ll need to go out just after sunset. Also, you’ll have to find a western horizon unencumbered by trees and buildings. Finally, dig up that pair of binoculars you were hoping to use at OSU football games this fall.

Look as soon as you can, tonight if possible. Mercury moves quickly as it orbits the sun. You won’t get many evenings before it disappears again into the sun’s glare.

This time around, the planet can be seen in evening twilight — that period in the evening just after the sun has set but its glow is still in the sky.

Mercury will be an orange-red, star-like point low in the west. Tonight, look for it near the planet Venus, which has shone so brilliantly in the western sky these last couple of months.

If the sky is clear tonight, start observing about 15 minutes after sunset. I cannot emphasize that last part enough. Whatever you do, don’t try to observe Mercury before the sun has completely set. Remember that Mercury is always close to the sun. Even a momentarily accidental view of the sun, especially in binoculars, can be extremely and permanently harmful to your vision.

As the sky darkens, Venus will pop out of the surrounding sky glow first. Now grab your binos and point them at Venus. Scan just below Venus, nodding your head and binoculars very slowly.

You should be able to see an orange-red point of light. That’s Mercury. If you don’t see it the first time, keep trying for about 15 minutes to allow the sky to get darker.

Just one night later (Wednesday evening), Mercury will be even closer to Venus but still below it. By Thursday evening, Mercury will have moved even closer, close enough below Venus that you might be able to fit both planets in a single binocular field if your binos have a wide enough field of view.

By Friday, Mercury has moved just to the left of Venus and slightly above it. By Saturday evening, Mercury is now farther up and to the left.

Let’s hope for a crystal-clear sky on Sunday. The moon will make an appearance as a slim, two-day-old crescent. Find it first. Now find Venus down and to the right. Mercury will appear as a dim point of light right between and equally distant from Venus and the moon.

Your binoculars won’t help you much to see any detail on the planet. Mercury is small — 3,000 miles across compared to Earth’s 8,000 — and it’s tough to see the planet as a disk unless you have a telescope. Even then, you still won’t see much.

Binoculars might help you to spot Mercury, but they won’t be much help on Venus, which is easily visible to the naked eye, of course, but it is too far away to resolve into a disk.

A telescope will help you to see both planets as featureless disks. I know that doesn’t sound like much, but I have seen the disk of Mercury only a few times in my long stargazing career. For starters, you’re looking at the smallest planet.

Even worse, to see objects such as Mercury near the horizon, you must look through a thick layer of our atmosphere. As the air bubbles and boils, it carries the image of the planet with it, making it blurry. It takes a rare, steady night to see Mercury as anything but a blob.

Despite its elusiveness, the planet Mercury has fully established itself in ancient and modern culture.

Because the metal mercury, or “quicksilver,” is liquid at room temperature, it skitters quickly across a surface.

Fickle, erratic, and quick-witted people who change their minds a lot are called mercurial.

The Roman god Mercury, identified with the Greek god Hermes, was the messenger of the gods. He had to travel quickly. The gods got testy when their messages weren’t delivered on time.

Mercury is often pictured with wings on his feet. I have always wondered where he bought his socks. Lately, he’s fallen on hard times. The god business just isn’t what it used to be. He now delivers flowers for a living. (If you don’t get the joke above, try googling “FTD logo.”)

In Roman times, he was also the patron god of public speaking and thus politicians who are quick with their tongues. He was also the god of thieves, especially pickpockets, who are quick with their hands. Any implied connection between the two occupations is totally coincidental, by the way.

When we look in the sky at the planet Mercury, it’s easy to see why the ancients associated it with such a fleet-footed fellow. As the closest planet to the sun, Mercury zips around it once every 88 days.

So there they are, having what must have looked like a very important rendezvous to the ancients. Out of such events came the old superstition called astrology. That’s right, astrologists. You are worshipping gods like Mercury and Venus when you try to predict the course of your life by noticing that the two planets are having an intimate encounter in the constellation Taurus.

Try stargazing instead. If you manage to spot Mercury, you will become one of the select few people living on Earth right now who have seen the closest planet to the sun.

By Tom Burns


Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.