Wednesday, May 22, 2013

The Gang is all Here!

A few days ago I advised you to look to the west
to watch the beginning of the biggest sky grouping of the year.  Last night's clouds blocked the last guest, but tonight's mostly clear skies revealed the last of the trio, Mercury, to the evening sky!  For the next week if you have a clear western horizon you should easily be able to spot the giant planet Jupiter slowly sinking towards the sun, the brilliant Venus slowly getting higher night by night, and slightly fainter Mercury popping up over Venus the next couple nights.  Jupiter won't tarry long and continue towards the sun, leaving just Venus and Mercury to rule the evening sky, Mercury staying above Venus for almost a month!  Most of the world's population has never seen the innermost planet Mercury, and this is an excellent chance to spot it during this planetary alignment.  For a starting guide, the left image was taken after sunset this evening, the right image is the same one with labels to let you know the players...  Click on the images to load the full-size view.

The best time to look for the trio is about 30 minutes after sunset.  The window lasts about 30 minutes - by that time (1 hour after sunset) they are getting too low to see.  Note that while the three planets will appear very close to each other in the sky, fitting in a single binocular field for a night or two, in actuality they are close only viewed from Earth's perspective.  Jupiter is some 550 million miles away, Venus and Mercury, while still on the far side of the sun from us are 150 and 110 million miles away.

Meanwhile, get out every clear night to take in the show.  The next triple planet conjunction is at least 2 years away, so get 'em while they last!

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