You are here

Annular Eclipse

February 26, 2017

Skywatchers in parts of South America and Africa are in for a treat today: a solar eclipse. Unfortunately, though, it’s not a total eclipse, but an annular one. That means a thin but bright ring of sunshine will outline the intervening Moon.

Solar eclipses occur when the new Moon passes directly between Earth and the Sun. When the alignment is just right, the Moon covers the entire solar disk, briefly turning day into an awe-inspiring twilight.

But the Moon follows a slightly elongated path around Earth. So if an eclipse occurs when the Moon is farthest from us, the Moon isn’t quite big enough to cover the entire Sun, leaving a ring of sunlight.

And that’s just what happens this morning across a narrow path that stretches from South America, across the Atlantic Ocean, and into southern Africa. The Moon will cover up to 98 percent of the Sun, leaving plenty of sunlight. Still, the sky will turn dusky, the air will get cooler, and beams of sunlight shining through leafy trees will project bright rings on the ground — good clues that something important is happening in the sky.

This is the first of two solar eclipses this year. The second takes place in August. It will slice across the width of the United States. Even better, it’s a total eclipse, so the Moon will cover the entire Sun. That will briefly expose the Sun’s hot but faint outer atmosphere, known as the corona — one of the most awe-inspiring of all astronomical sights.

More about the Sun tomorrow.


Script by Damond Benningfield

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.