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.
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.
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).more