Three Planets Dance in the West After Sunset

By Phil Plait

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Posted Monday, May 27, 2013, at 2:14 PM

Speaking of sunsets, over the past few days and for the next few as well, the planets Jupiter, Venus, and Mercury can be seen together in the west just after the Sun slips below the edge of the Earth. This is called a conjunction, and you don't need any fancy equipment to see it; just your eyes, and a clear view to the west.

If you pick your spot carefully, the foreground might enhance what you see, though. The brilliant astrophotographer Thierry Legault went to the northwest coast of France, and on May 26, 2013 took this ridiculously beautiful picture:

Three planets over a tidal island. Click to conjunctivate.
Photo by Thierry Legault, used by permission.

Mon dieu! That's Mont-Saint-Michel, a tiny island off the French coast. It's a tidal island; the causeway connecting it to the mainland is submerged at high tide and exposed during low tide. A monastery sits upon it, making it look like something out of a fantasy story. I've never been to that part of France, but it's on my list now!

In the sky above and around it you can see Venus (lower right), Mercury (upper right), and mighty Jupiter (to the left). All three are unresolved dots at this magnification, but they may look different sizes because of their varying brightnesses. If the size variation were real, Jupiter would look three times bigger than Venus, and five times bigger than Mercury in the picture! Currently, all three are on the other side of the Sun, making them appear smaller than they can be. Mercury is actually the closest right now, about 170 million kilometers (105 million miles) distant, compared to 250 million km (150 million miles) for Venus and 910 million km (565 million miles) for Jupiter.

Think on that: Jupiter is so flipping big that even though it's nearly four times farther away from us than Venus, it still looks much bigger through a telescope!

Photographer Ken Griggs also had a great view of the conjunction on May 26 in Lehigh Valley, Pennsylvania, and this photo appears to be celebrating it:

Celebrating the planetary conjunction. Click to enpyrenate.
Photo by Ken Griggs, used by permission.

I'll note it's actually a composite of two different photos; both had the fireworks and planets in them but added together made the picture even more pleasing.

As the days go on, Jupiter will sink lower to the horizon after sunset as Venus and Mercury climb higher, so this configuration will constantly change. It's best this week, though, so go out and take a look. It's a rare opportunity to watch these three worlds dance together in the sky.