UMass Amherst Public Sunwheel Event Marks the Autumnal Equinox

The public is invited to observe sunrise and sunset associated with the day of the autumnal equinox among the standing stones of the UMass Amherst Sunwheel on Monday, September 22 at 6:30 a.m. and 6 p.m. These events mark the astronomical change of seasons when days and nights are nearly equal in length in the Northern Hemisphere.

From the Sunwheel, observers standing at its center will see the sun rise and set over particular stones placed to mark the equinoxes.

UMass Amherst astronomers will discuss the celestial cause of the sun's changing position during the hour-long gatherings. They will also explain the seasonal positions of Earth, the sun and moon, and answer other questions about astronomy.

The exact minute of the autumnal equinox this year is 2:19 p.m. Eastern Daylight Time on Sept. 22. This marks the moment that the sun crosses the celestial equator from north to south as seen from Earth, ushering in the beginning of fall in the Northern Hemisphere. On the day of the equinox (for equi, "equal" and nox, "night"), an observer located on Earth's equator will see the sun pass directly overhead at local noon, and it marks the beginning of six months of daylight at the South Pole and six months of nighttime at the North Pole. On every day other than the equinox, either the Earth's Northern or Southern Hemisphere is tilted toward the sun.

For observers, except those at the North and South Poles, the sun on the equinox rises due east for 12 hours and sets due west for 12 hours.

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 should be prepared for wet footing, and mosquito repellent is highly recommended. Heavy rain cancels the events, but the talks will be given if there are clouds or light rain. For last-minute changes, please check https://www.umass.edu/sunwheel.