Eclipses explained

What is a ‘hybrid’ solar eclipse?

A rare hybrid solar eclipse will next occur in 2031. Here’s what that means and how it will affect eclipse-chasers

What once-a-decade phenomenon next happens on November 14, 2031, in the Pacific Ocean? A hybrid solar eclipse (HSE), of course, is a bit of both a total solar eclipse and an annular solar eclipse. Sometimes they’re called an annular-total or total-annular eclipse.

A hybrid solar eclipse explained

“A hybrid eclipse is one which is annular when the path first touches the Earth, and/or leaves the Earth, but which becomes total for a period in-between,” says Australian astronomer Dave Herald. So how come it becomes total? “The shadow of totality is a cone,” he says. “For a total eclipse, the point of the cone passes below the Earth, and for an annular eclipse, the point of the cone passes above the Earth, never touching it.” It’s all down to the curvature of the Earth.

Understanding the ‘shadow cone’

Hybrid solar eclipses are a bit of both those kinds of solar eclipses. “For a hybrid eclipse the point of the cone passes through the Earth,” says Herald, “For some locations, the point is above the Earth’s surface, and the eclipse is seen as annular, and in other locations it passes below the surface of the Earth, and the eclipse is seen as total.”

Why is an HSE rare?

The difference between a shadow cone passing above and below Earth is slight, making hybrid eclipses unlikely. “Hybrid eclipses are rare because the range for the location of the point of the cone is quite small,” says Herald.

The three HSE experiences

All this means there are three forms of eclipse experience during a hybrid solar eclipse, depending on exactly where you stand. The first is a true annular eclipse, with an unbroken ring of light, and the third is a true total eclipse. However the scenario in the middle – viewable at the transitional point between an annular and a total eclipse – is the most interesting (and least seen). “It’s a broken-annular eclipse, where the ring of light is broken by lunar mountains,” explains Herald. “It is effectively a series of Baily’s beads around the complete circumference of the moon (where) the number of Baily’s beads increases, then decreases, as one moves from the point of full annularity to the point of full totality.”

Hybrid solar eclipses are relatively rare. After November 14, 2031, two come along in quick succession in 2049 and 2050. However, for most eclipse-chasers heading to the Path of Totality in 2031 – likely on a cruise ship – it will be just a normal total solar eclipse … if there is such a thing!

Pic credit: Pixabay