Book 3, Question 49
Why Is the Sun So Bright?
The Sun is a giant ball of hot gas, like a huge fusion lamp! Deep in its core, hydrogen slams together and becomes helium. That fusion dumps huge energy as light and heat.
From the book
Page from A Million Whys Book 3
More fun facts
- The Sun is a yellow dwarf star about 4.5 billion years old.
- The Sun is a huge ball of hydrogen and helium, held together by its own gravity.
- When the Sun was young, it was not as bright and gave off less heat than it does today.
- The way the Sun makes its energy causes it to slowly get brighter and hotter over time.
- Scientists wonder how early Earth stayed warm enough for life under the dimmer young Sun. A thick blanket of gases in the air may have helped.
- NASA's Solar Dynamics Observatory watches the Sun and has photographed bright solar flares bursting from its surface.
Sources: NASA Science, NASA, NASA Space Place
Questions kids ask
Was the Sun always this bright?
No. The young Sun was dimmer and cooler, and it has slowly grown brighter over billions of years.