When the Moon passes between the Earth and the Sun, it casts a shadow on Earth that temporarily obscures part or all of the Sun's disc. This is called a solar eclipse. When the entirety of the Sun is blocked out by a New Moon, it's referred to as a total solar eclipse, and only happens when these three celestial bodies are properly aligned. If the Moon is too far away during the eclipse, the darkest part of its shadow, or umbra, may not completely reach the Earth; therefore, only a partial eclipse takes place.
On average, a total solar eclipse is visible from somewhere on the Earth's surface every eighteen months. The sky show can last several hours, although totality may range from a few seconds to approximately eight minutes. Only places that are located in the Moon's umbra can see a total solar eclipse; and the longest one thus far in the 21st century occurred on July 22, 2009, when totality was recorded at six minutes and thirty-nine seconds.The next eclipse is slated for December 14, 2020, and will be visible for some folks in Southern Africa, much of South America and parts of Antarctica.
On this day in 1851, the first scientific photograph of a total solar eclipse was captured by Julius Berkowski at the Royal Observatory in Königsberg, Prussia. This particular image caught a still of the Sun's corona, which is normally invisible due to the brightness of the solar disc. Berkowski was specifically commissioned by the observatory because he was a skilled daguerreotypist, and with these talents, he was able to make an eighty-four second exposure shortly after the beginning of totality.
Fun Fact: The eclipse image was entered as member 14 in a photographic series called Solar Saros 143, which contains various pictures of seventy-two events, including partial and total eclipses, annual eclipses and hybrid events (when the distance between the Earth and Moon is so balanced that the curvature of the Earth is brought into the equation). So, now ya know, friends!