Bright Planetary Conjunctions Liven Up This Week’s Evening Sky

by Bob King on May 22, 2013

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Three bright planets gather in the northwestern sky this week. This map shows the sky 30 minutes after sunset from the middle latitudes. Stellarium

Three bright planets gather in the northwestern sky this week. This map shows the sky 30 minutes after sunset from the mid-northern latitudes. Venus stands about 6 degrees high at that time. Stellarium

Planning a barbecue this weekend? You may want to top it off with a look at three bright planets shuttling about the western sky at dusk. Jupiter, Venus and Mercury gather for nearly a week of delightful alignments including three separate conjunctions staring right now. Mercury and Venus pair up on Friday; Mercury and Jupiter on Sunday and Venus and Jupiter on Monday. All three form a series of ever-changing triangular arrangements as the nights go by.

Three bright planets will highlight the northwestern sky this week and early next. Mercury is shown in pink and Jupiter in yellow. Stellarium

Three bright planets will highlight the northwestern sky this week and early next. Mercury is shown in pink and Jupiter in yellow. Time is 30 minutes after sunset facing northwest. They’ll be closest together – less than 3 degrees apart – on the night of the 26th. Stellarium

Brightest of the bunch is Venus followed by Jupiter and then Mercury. The key to seeing them all is a clear sky and unobstructed view of the west-northwest horizon. Best time for viewing is a half hour to 45 minutes after sunset. Although the diagrams make the planets look like largish disks, difference in size is a device to show their brightness. Bigger means brighter.

Mercury gradually climbs higher in the coming days, Venus will remain in nearly the same spot and Jupiter slowly drops off toward the horizon. Seeing three planets bunch up isn’t rare, but it is unusual – all the more reason to go for a look if your skies are clear. Alignments like this occur because all 8 planets lie in essentially the same flat plane. As we look across the solar system, sometimes near planets and far planets lie along the same line of sight and appear side-by-side in the sky. They may look close to each other but of course they’re millions of miles apart.

Positions of the planets on May 27. The arrow shows our point of view from Earth. Notice that the line of sight through all three takes our gaze near the sun. That's why they're only visible shortly after sunset in a bright sky. Click image to see a cool, interaction planet display. Credit: dd.dynamicdiagrams.com

Positions of the planets on May 27. The arrow shows the point of view from Earth. Notice that the line of sight through all three takes our gaze near the sun. That’s why they’re only visible shortly after sunset in a bright sky. Click image to see a cool, interactive planet display. Credit: dd.dynamicdiagrams.com

This week Venus is 154 million miles (248 million km) from Earth, Mercury 113 million (182 million km) and Jupiter a distant 562 million (904 million km). The planet position diagram above will give you a sense of their current arrangement in space.

Whenever you go planet-seeking in bright twilight, I always recommend bringing along a pair of binoculars. They penetrate haze and make finding these bright little dots much easier. Enjoy the show!

About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

Gadi Eidelheit May 23, 2013 at 1:15 AM

I took a photograph of them yesterday. Will try today as well.
http://www.thevenustransit.com/2013/05/jupter-venus-and-mercury.html

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