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The public is invited to join University of Massachusetts Amherst astronomers to observe sunrise and sunset on the longest day of the year among UMass Amherst Sunwheel’s standing stones on Friday, June 20 at 5 a.m. and 7:30 p.m. UMass Amherst astronomer Stephen Schneider, who will lead this event for the final time after doing so for the past 14 years, will explain the astronomical cause of the solstice and how the Sunwheel works.

At 10:43 p.m. EDT on June 20, the sun will reach its northernmost position relative to the stars as seen from Earth. This marks the astronomical start of summer in the Northern Hemisphere and winter in the Southern Hemisphere. On the solstice, daylight is longest and nighttime is shortest in the Northern Hemisphere. The sun also reaches its highest point all year at local noon for everyone living north of the tropics. The sun passes straight overhead, on this day only, for people living along the Tropic of Cancer.

From the center of the Sunwheel, the sun rises and sets farthest north at spots along the horizon marked by tall standing stones. Other standing stones mark the changing positions of the sun and moon throughout the year, much like ancient calendar-stone sites such as Stonehenge where thousands gather to view the summer solstice sunrise.

The sun’s northerly position changes so gradually around the date of the solstice that it rises and sets at almost the same position for more than a week. This is the origin of the word solstice, which means “sun stationary.” Sunwheel visitors who stop in on their own will be able to see the sun rising and setting over the summer solstice stones from roughly June 15–25.

At the evening session, if the sky is clear, a solar telescope will be set up to safely view the surface of the sun. During this period of strong solar activity, sunspots and solar prominences are often visible.

The UMass Amherst Sunwheel is located south of McGuirk Alumni Stadium, just off Rocky Hill Road (Amity Street) about one-quarter mile south of University Drive. Visitors to the Sunwheel should be prepared for wet footing and mosquitoes. The events will be canceled in the event of heavy rain. For more info, please visit the Sunwheel website.