Dawn Serves Up Mercury With A Splash Of Orion Sauce

Look for Mercury this week in the dawn sky. It shines low in the northeast below Castor and Pollux in Gemini. I set the date on the chart to Aug. 8, but it will be in nearly the same location all week and next, growing brighter throughout. Stellarium

The aurora will do what it will do. And it didn’t do anything last night. A no-show. While that can be frustrating, especially if you made a special trip to the country in hopes of seeing it, isn’t that nature’s way? Always a little cagey, refusing to be pinned down. I hope at least you got an eyeful of the stars and the sinking moon. We had a mix of clouds of stars at my home.

Guess who’s out at dawn? Be-boppin’ Mercury, the solar system’s fastest planet, that’s who. You can see it if you’re willing to sacrifice a little sleep. There’s always the bonus of catching a sunrise, too. Mercury is currently near its greatest elongation — as far west of the sun as it gets — and visible low in the northeastern sky about 45 minutes before sunrise.

To see it, find out your local sunrise time and back off that time one hour. You’ll also need to stand somewhere where you can see low down in the northeastern sky. Mercury will hover not quite a fist above the horizon and shine around magnitude 0 or equal to Vega, the brightest star in the Summer Triangle asterism. It won’t look that bright though because of low altitude and competition from the dawn light, but assuming clear skies, you should be able to seize a view. (Update: Right now (Aug. 6,7) it is still a little faint because of twilight but easily found in binoculars below Castor and Pollux. It should become easier to see without optical aid in the coming week as it brightens.)

This is probably the earliest I’ve seen Orion come up in the east. I took this photo on July 30 at mid-dawn as one-by-one the stars rose over Lake Superior. It was so cool to watch the three belt stars in binoculars come up almost vertically. Orion will be higher up now — a full week later — and easier to see. Bob King

Stick around for sunrise, too. When was the last time you saw a sunrise? I’m embarrassed to admit it’s been at least a month for me. I promise to follow my own advice later this week when I head out on my personal Mercury mission. Now, if you’re out a little more than an hour before sunrise, you’ll get a taste of winter. That’s because Orion is returning to the morning sky after several months of invisibility. Look off to the southeast to find orangey Betelgeuse (altitude ~15°) and below it the Belt and Rigel.

(Left): In June the sun shines from the same part of the sky as Orion so we can’t see the constellation. Once the sun has moved away — due to Earth’s orbital motion around the sun — Orion becomes visible at dawn in August (right). Stellarium

Earth’s motion around the sun makes the sun appear to move across the sky day-to-day, week-to-week and month-to-month. Right now the sun is in the constellation Cancer and will cross over into Leo on Aug. 11. Whatever constellation the sun is near is invisible — lost in the glare of daylight. Orion was lost in that glare during May, June and July because the sun shone from Taurus and Gemini, constellations not far from Orion. The Earth has since moved along its orbit, placing the sun in Cancer the Crab and far enough away from our favorite winter constellation so it can finally roam free in the pale dark of dawn. As the sun continues to move eastward, Orion will rise earlier and earlier and grow brighter and easier to see.