Explore the Universe

Public sunrise and sunset gatherings explore the astronomy of the changing seasons

The public is invited to join UMass Amherst astronomers among the standing stones of the campus Sunwheel on Tuesday, Sept. 22, at 6:30 a.m. and 6 p.m. The sunrise and sunset gatherings will mark the autumnal equinox and offer an opportunity to connect the changing seasons with Earth’s motion around the Sun.

During each hour-long gathering, astronomers will use the standing stones to explain why the Sun’s rising and setting positions change throughout the year, how Earth’s tilt produces the seasons, and how the Sunwheel carries on a long tradition of marking these patterns. There will also be time to discuss the Moon and answer other questions about astronomy. Visitors of all ages are welcome - no astronomy background is needed. Bring your questions and your curiosity. Weather permitting, the evening gathering will also feature views of the Sun through specially filtered telescopes before sunset.

The equinox itself occurs at 8:05 p.m. Eastern Daylight Time on Sept. 22. It marks the Sun’s crossing of the celestial equator, Earth’s equator projected onto the sky, from north to south. This is the astronomical beginning of fall in the Northern Hemisphere and spring in the Southern Hemisphere.

Around the equinox, the Sun rises nearly due east and sets nearly due west. At the Sunwheel, standing stones mark these directions, allowing visitors at the center of the circle to see the connection between the Sun’s position on the horizon and the time of year. Weather permitting, participants will watch these alignments during the gatherings.

Although “equinox” means “equal night,” day and night are not exactly equal in length on the equinox. The Sun’s apparent size and the bending of sunlight by Earth’s atmosphere give us a few extra minutes of daylight. Here in Amherst, the closest balance between day and night comes a few days later.

The UMass Amherst Sunwheel is located south of McGuirk Alumni Stadium, just off Rocky Hill Road, about one-quarter mile west of University Drive. Visitors should dress for the weather and be prepared for wet grass underfoot. Mosquito repellent is strongly recommended. Heavy rain cancels the gatherings. More information and weather-related updates are available at https://www.umass.edu/astronomy/

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