Two days ago, I got my COVID-19 booster and experienced flu-like symptoms with aches and pains. But that wasn't going to stop me from seeking Mercury, so I set the alarm for 6:15 a.m. and drove to a big field with a wide-open eastern view. I expected it might take a minute of searching to spot the planet in the twilight glow. Instead, it shone brightly in the dawn light as a solitary "star" low in the east-southeast sky. So easy!
That's why I'm sharing the news with you. If you've never seen this elusive planet the time has arrived. Now through the first week of November, it makes an excellent appearance at dawn between 90 minutes and 50 minutes before sunrise. Where I live, the perfect viewing window is from 6:15 to 6:45 a.m. Central Standard Time.
Although Mercury is slowly moving back toward the sun (getting lower in the sky) it continues to brighten. Tomorrow morning it shines at magnitude -0.7, brighter than any star visible from mid-northern latitudes except Sirius. Twilight tempers that brilliance to be sure, but not so much that it hinders seeing the planet.
When you look at Mercury, consider its size. At 3,030 miles (4,876 kilometers) across or just 1.4 times the diameter of the moon it's the smallest of the eight planets. Given its current distance from us of about 89 million miles (143.5 million kilometers), it's amazing that we can see it at all — and brightly at that.
Mercury circles the sun in just 88 days, completing more than four orbits during the time it takes Earth to make just one. When it reaches its maximum distance east of the sun, we see it at dusk. When it's west of the sun, it's visible at dawn. We typically have seven appearances (called "apparitions") of the planet each year — several at dusk and several at dawn.
Not all apparitions are equal. The angle the planet's path makes to the eastern or western horizon greatly influences its visibility. If that angle is shallow, Mercury hunkers down close to the horizon, and it's difficult or impossible to see. But when the angle is steep, as it is now, the orb stands well above the sun and climbs high enough to clear the treetops and horizon haze. For northern hemisphere skywatchers, Mercury's current morning appearance is the best of 2021.
Like Venus, the other inner planet, Mercury shows phases. When it swings to one or the other side of the sun we see half its rocky globe illuminated like a half-moon. That's where we're at right now, with Mercury as far to the west of the sun as it will get this apparition. If you have a small telescope that can magnify 50-75x, you'll see its phase slowly change from half to gibbous over the next two weeks.
As our recent warm weather slips away and signs of the coming winter appear, we should be grateful that on Earth, seasonal changes are gradual. Not so on Mercury. With essentially no atmosphere, it's either incredibly hot, with temperatures reaching a scorching 800 degrees Fahrenheit (430 degrees Celsius) during the daytime, or bone-chilling, with nighttime lows of 330 degrees below zero Fahrenheit (201 degrees below zero Celsius). From the planet's surface the sun appears more than three times as big as it does from Earth and sunlight seven times brighter.
And while a day on Earth seems to go by quickly you wouldn't have that problem on Mercury, where one full day-night cycle takes 176 days. Hot, cold, barren and crater-pocked like the moon, it's a forbidding planet, yet its presence at dawn feels strangely welcoming.
You can explore Mercury anytime with just your fingers. In the interactive map below, click and drag your cursor to spin the planet, and scroll to zoom in and out.
"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.