AMHERST, Mass. – The public is invited to observe sunrise and sunset live, but remotely online, on the day of the autumnal equinox among the standing stones of the UMass Amherst Sunwheel on Tuesday, Sept. 22 at 6:30 a.m. and 6:15 p.m.
UMass Amherst astronomer Stephen Schneider plans to hold the two online public events to mark the change of seasons when days and nights are nearly equal in length around the world.
Details for joining the online events will be posted on the UMass Amherst Astronomy Department’s website at www.astro.umass.edu and the Sunwheel website at www.umass.edu/sunwheel the day before the event.
Weather permitting, the sun will be observed as it rises and sets over the eastern and western standing stones of the Sunwheel. Via web broadcast, Schneider will discuss the astronomical cause of the sun’s changing position. He will also explain the design and history of the Sunwheel and how it marks the changing positions of the sun and moon.
The precise astronomical time of the autumnal equinox this year is 9:30 a.m. Eastern Daylight Time on Sept. 22. This marks the moment when the sun crosses the celestial equator from north to south as seen from Earth, ushering in the beginning of fall in the Northern Hemisphere and spring in the Southern Hemisphere. It marks the beginning of six months of daylight at the South Pole and six months of night at the North Pole. On any day other than the equinox, either the Northern or Southern Hemisphere tilts toward the sun.
On the equinox (for equi, “equal” and nox, “night”) the sun very nearly rises due east and sets due west and stays up for 12 hours and down for 12 hours, except as seen from the North and South Poles, where the sun circles the sky, skimming the horizon. From the Sunwheel in Amherst, observers standing at the center of the standing stones see the sun rise and set over stones placed to mark the equinoxes.