‘Ring of fire’ solar eclipse this week: What is an annular eclipse?

annular-eclipse-zion-national-park(GEOFF HORNER/ GEOFF HORNER PHOTOART)

On Thursday and Friday, skywatchers in parts of Australia and the Pacific region will be treated to a spectacular “ring of fire” solar eclipse, in which the moon blots out all of the sun except for its outer edge.

Here’s what you need to know about this stunning skywatching event, which is also known as an annular solar eclipse.

What is an annular eclipse?

The orbit of the Earth around the sun is an ellipse, not a circle. This means that sometimes Earth is closer to the sun than at others. The same goes for the moon’s orbit around Earth, which is also elliptical rather than circular. [See Spectacular Photos of a ‘Ring of Fire’ Solar Eclipse]

We are fortunate to live in a time when the sun and the moon are very close to the same apparent size in our sky. This is an illusion of perspective: The moon is small (2,159 miles wide) and close by (238,855 miles away) while the sun is large (865,278 miles wide) and far away (92,955,808 miles).

Notice that the sun is about 400 times larger than the moon in diameter. It is also about 389 times farther away. This explains why the two appear to be almost the same size in the sky. But “almost” is not exact, which explains why there are different kinds of solar eclipses — partial and total.

 

Fox News has the full article

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