Science behind an astronomy picture of the day photo

ECLIPSE

Science behind an APOD Photo

A rare hybrid solar eclipse: Analyzing the science of a photograph

Although solar eclipses are striking in and of themselves, the 2005 eclipse in the NASA photograph was notable given that "a total or an annular eclipse could be seen depending on the observer's location" causing it to be labeled a hybrid eclipse (Nemiroff & Bonnell 2013). A photograph was captured of a total eclipse with the shadow of the moon covering the sun for a few minutes, as taken by a photographer named Fred Espenak on a ship "about 2,200 kilometers west of the Galapagos, the eclipse was total, the lunar silhouette exactly covering the bright solar disk for a few brief moments. His camera captured a picture of totality revealing the extensive solar corona and prominences rising above the Sun's edge (Nemiroff & Bonnell 2013). In contrast, another photographer from a different vantage point near Panama took a photograph which suggested that the "Moon's apparent size had shrunk enough to create an annular eclipse, showing a complete annulus of the Sun's bright disk as a dramatic ring of fire" (Nemiroff & Bonnell 2013).

Such hybrid eclipses are extremely rare: only 3.1% of all eclipses are of this variety (Nemiroff & Bonnell 2013). The photograph shows two halves of the eclipse, depicting both men's photographic vantage-points. This photograph is worthy of record because of the phenomenon's rarity and also because the fact that both men were able to take such perfect photographs of different sides of the phenomenon. "Today's hybrid solar eclipse is most widely visible beyond the central shadow track as a brief partial eclipse from northeastern Americas through Africa, and along the track in an annular phase for only the first 15 seconds" (Nemiroff & Bonnell 2013). However, through the communication facilitated by the Internet, people in precisely the right locations can take different photographs of the phenomenon, and collectively show its different aspects in ways which were never possible before. Given that this phenomenon "won't be seen again for nearly another 160 years -- in 2172," the photographic dedication of the picture-takers is especially laudable (Sappenfield 2013).

In most instances, eclipses are either annular or total. "If an eclipse occurs when the moon is farther away, the moon as viewed from Earth is not big enough to completely blot out the sun. That means a thin 'ring of fire' is visible around the moon. This is an annular eclipse…If an eclipse occurs when the moon is closer to Earth, and then the disk of the moon is big enough to completely blot out the sun. All that can be seen is the sun's brilliant outer atmosphere, or corona. This is a total eclipse" (Sappenfield 2013). With a hybrid eclipse, thanks to the shape of the earth "curvature of the Earth actually reached up to intercept the point of the moon's umbra" like an annular eclipse but "as the eclipse progressed, the curvature of the Earth actually reached up to intercept the point of the moon's umbra, making it a total eclipse" (Sappenfield 2013).