What Happens When the Sun Gets Bigger

The Sun may seem eternal, but it won’t stay the same forever. In about 5 billion years, the Sun will go through a major change — it will become much bigger than it is today. This is a normal part of a star's life cycle.

Right now, the Sun is in the "main sequence" stage. That means it's steadily burning hydrogen into helium in its core to produce light and heat. But over time, the Sun will run out of hydrogen fuel. When that happens, the core will shrink, and the outer layers will expand. The Sun will turn into a red giant — a huge, cooler, and brighter version of itself.

As it grows, the Sun could expand so much that it swallows the inner planets, including Mercury and Venus. Earth might be next. Even if it escapes being swallowed, the heat from the red giant Sun would boil away Earth’s oceans and destroy all life.

After a few million years as a red giant, the Sun will shed its outer layers into space, forming a glowing cloud called a planetary nebula. What’s left behind will be a small, dense core known as a white dwarf — no longer producing energy, but still glowing with leftover heat.

It’s a dramatic future, but nothing to fear right now. The Sun still has billions of years left before this happens. For now, it continues to shine and support life on Earth every single day.