What is Sun’s limb?

The Sun’s limb is like the edge of a giant round cookie you see when you look at it from far away.

Imagine you're sitting on the floor of your kitchen, looking up at a big round cookie on the table. You can see the whole cookie, its top, bottom, and sides. But if you were really small, like a tiny bug crawling along the edge of that cookie, what would you see? You’d mostly see the side of the cookie, that’s like the Sun’s limb.

When you look at the Sun from Earth, sometimes it looks like it's just a round disk in the sky. But if you watch carefully during sunrise or sunset, you can see its edge clearly, that’s the limb! It’s like watching the cookie being lowered slowly out of view.

Scientists study the Sun’s limb to learn about the Sun's atmosphere. Just like how you might notice crumbs on the edge of a cookie, scientists look for clues on the Sun’s limb, things like light and heat that behave differently near the edge than in the middle.