Professor Don Pollacco comments on the rare 'hybrid' solar eclipse happening this week
".... However it is slightly inclined to Earth’s orbit so instead every 12-18months the moon eclipses the sun and the rest of the time it passes either above or below the sun in its orbit.
“By a quirk of nature the apparent size of the Moon and the Sun are much the same (the Moon is tiny compared to the sun but is very close to the Earth) and when an eclipse happens, if you stand where the alignment is best (every 12-18months), you can see the Sun’s disk completely covered by the Moon – this is called a Total Solar Eclipse. These events are amazing as you can see the atmosphere of the Sun at that time and, of course, it gets dark as the sun is blotted out.
“The path of totality on the Earth is thousands of miles long but only about a hundred miles wide. Away from the track and the Moon doesn’t completely cover the Sun, you see a partial eclipse which is no-where near as exciting to watch. While a total eclipse occurs every year or so the likelihood of it occurring from any particular place is low. Often they are visible from remote places and rarely over large cities.
“The Moon’s orbit around the Earth isn’t quite circular but is flattened into an ellipse slightly. Consequently, sometimes the Moon can be slightly closer or further away from the Earth at the time of total eclipse. If the Moon is closer, it appears slightly bigger and the eclipse last a few minutes (the longest total eclipse is about seven minutes). If the Moon is slightly further away, it seems to be smaller than the Sun disk. At this time, you can see a ring in the sky called an annular eclipse. These eclipses are more like partial eclipses, as you don’t see the Sun’s atmosphere.
“Very occasionally, the Moon is at the right distance so that it appears exactly the same size as the Sun disk. In these cases, a total eclipse that last just few seconds may occur. This is called a hybrid eclipse. While very short in duration, they can be very dramatic as the sun at the central part could be shining through valleys on the lunar disk and also the Sun’s atmosphere. If you were unlucky, you may just see an annular eclipse. In fact, along the track, which will be very narrow, you could see a total eclipse and then an annular eclipse in different places.”