642
For the first time in 18 years all five planets visible to the naked eye will be in the sky together throughout June. Mercury, Venus, Mars, Jupiter and Saturn will appear in sequential order across the night sky.
Planetary alignments of this magnitude happen only once every two decades. The next one won’t happen again until 2040.
To experience this rare event you’ll need to be somewhere with a clear view of the horizon to the east about 30 minutes before sunrise. On June 24 the view will be made even more special with a waning crescent moon appearing between Venus and Mars.
– Carlisle Willard, The Kentucky 100