The Sky This Week: Welcome, summer!
Summer evening: The summer solstice occurs June 20, bringing the longest day of the year and kicking off the summer season in the Northern Hemisphere.
Friday, June 18
An hour after sunset, the bright red star Antares, located in Scorprius, is visible above the southern horizon. This magnitude 1 star is located in a rich region of the sky rife with star clusters, including M4, a globular cluster less than 1.5° due west of Antares. M4 is an easy magnitude 5.6 and spans about 36'. At just 7,200 light-years from Earth, it’s one of the nearest globular clusters to our planet. Many observers can see a straight “bar” structure of 11th-magnitude stars within the cluster’s core.
Wait a little longer, and two open clusters — M6 and M7 — will appear as Scorpius’ tail clears the horizon. These are much younger, looser groupings of stars than M4, and excellent binocular targets for even beginning observers...