Discovering the Magic of Twilight: A Meteorologist’s Insight into Civil, Nautical, and Astronomical Twilight

A breathtaking display of nature, sunrise and sunset are the most beautiful times of the day. But what happens before and after these stunning moments? GBH meteorologist Dave Epstein recently shared insights with Morning Edition co-hosts Jeremy Siegel and Paris Alston about the science behind these wonderful displays of nature.

From civil twilight to astronomical twilight, there are different phases that occur before and after sunrise and sunset. Civil twilight is the period just before sunrise and after sunset when the sun is situated zero to six degrees below the horizon. This is a favorite time of the day for many people because it still provides light without the sun being visible. Sunrises and sunsets during civil twilight can be absolutely breathtaking, occurring approximately 30 minutes before sunrise or 30 minutes after sunset.

Nautical twilight follows civil twilight and takes place when the sun is six to 12 degrees below the horizon. During this time, the brightest planets and stars start to become visible. Animals are also more active during nautical twilight, with Epstein referring to it humorously as “coyote time” due to the increased activity of crepuscular animals like deer, which can sometimes lead to accidents with cars.

Astronomical twilight then occurs when the sun is between 12 and 18 degrees below the horizon. This is a time when faint objects, including the Milky Way, can be observed, but it is still not considered nighttime. In summer months like June, astronomical twilight occurs very early and late, resulting in short nights, particularly in northern New England where true nighttime may not begin until late evening and astronomical twilight is in the early morning hours.

Overall, understanding the different phases of twilight can enhance our appreciation for the beauty of sunrises and sunsets and provide insight into