As if we haven’t had enough excitement with the recent partial solar eclipse and coming transit of Venus and partial eclipse of the moon, you can now add one more event to your calendar – a conjunction of Venus and Mercury. That happens today at 3 p.m. Central time when the sun is high in the sky over the U.S. The two planets will be only 1/5 of a degree apart at the time. Very close!
Amateur astronomers who have the ability to precisely point their telescopes at a particular spot in the sky day or night can attempt to see the planetary pair in broad daylight. Once Venus is found, Mercury will be in the same field of view just north of the much brighter planet.
Take great care to avoid the sun, which will be only 6 degrees to the west. If you succeed, you’ll also witness one of the thinnest Venus crescents ever. A mere 0.7 % of the planet will be illuminated by the sun at the time. A word of caution: Do not attempt to find this with binoculars or you may accidentally point them at the sun and damage your eyes.
European observers are more fortunate. The conjunction happens around the time of sunset with the sun safely out of the picture. A wide-open horizon to the northwest, haze-free skies and a pair of binoculars will show brighter Venus, and next to it, the planet Mercury, shining at magnitude -1.6. That’s as brilliant as Sirius, the brightest star, but being so near the sun, the planet will appear much fainter.
U.S. observers can also watch the pair shortly after sunset; they’ll still be close together though not as tight as during the afternoon. Venus’ big crescent should be plain in almost any pair of binoculars.
I found slender goddess and star-like Mercury with my 4-inch refractor earlier this morning by using a solar filter to center the sun and then offsetting from it the appropriate distance. Venus was amazing as you might imagine, with Mercury easily visible to the west in the same field of view.
Although the two planets look like they might bump into each other, Venus is in the foreground in front of the sun 27.3 million miles from Earth, while Mercury’s in the background on the opposite side of the sun 120.5 million miles away. Their different locations in relation to sun and Earth also mean their phases aren’t the same: Venus is a crescent, Mercury looks like a tiny full moon through a telescope.
With each passing day, Venus gets closer and closer to transit time. We’re all excited about the event as we anticipate the rare and curious sight of a planet silhouetted against sun. The last pair of transits happened in 1874 and 1882, and most of us won’t be around for the next pair in 2117 and 2125. If Venus’ orbit were exactly in the same plane as Earth’s, we’d have a transit every 8 years when the planet passed through inferior conjunction. That’s when the two planets lie on a line on the same side of the sun.
Instead, the planet’s tilted orbit guarantees that most of the time Venus misses the sun when we line up, passing a little north (above) or south (below) it. How nice to finally hit the nail on the head next Tuesday.