Questions by kids: ‘How old is the sun, and how much older will it get?’

Learning is all about asking questions, and children ask the best questions. Boise State is home to more than 1,400 faculty members and researchers who are eager to answer these amazing questions.

"This photo was taken at Kitt Peak. I am sitting on an old telescope mirror test dummy or "the concrete donut" that was repurposed to be a mural. These dummies are used to test where actually telescope mirrors would go. They are of the same size and weight as what the mirrors would be," said Garcia Soto.

Today, astrophysics postdoctoral researcher Aylin Garcia Soto answers a child's question: "How old is the sun, and how much older will it get?"

At Boise State, Garcia Soto is part of Professor Brian Jacksons' research team, which studies the short period planet group or S(u)PerP(i)G/"Superpig".

"We search for planets around other stars that are spiraling into their star, such as WASP-12b," Garcia Soto said. "This planet is estimated to be absorbed or engulfed by its star in about 3 million years."

How old is the sun?

Just like we grow from a baby to a child, a teenager, an adult and eventually an elderly person, the Sun has a lifecycle, too. It's just billions of years longer than ours.

Right now, the Sun is a middle-aged adult star at about 4.6 billion (4,600,000,000) years old. Astronomers call this stable, adult phase the Main Sequence stage. The real change will happen in another 5 billion (5,000,000,000) years. The Sun will look completely different!

The Life Cycle of the Sun shows that earth is about 4.5 billion years old, and that over time it will gradually get warmer until it becomes a Red Giant star (a little over 5 billion years in the future). In the following 4 billion years, the Sun will run out of fuel, and slowly fade into a planetary nebula, then finally a white dwarf. Art Credit: NASA/JPL-Caltech

The Sun runs on fuel, much like a campfire made of gas. To start a campfire, we begin with small twigs. For the Sun, this starter fuel is made up of light hydrogen atoms inside a giant space cloud called a stellar nebula. This hydrogen fuel combines to create heavier, helium atoms, producing light and heat. The fuel also pushes outward, balancing gravity so the Sun doesn't collapse under its own weight.

To keep a campfire going once the twigs burn out, we have to throw in heavier piles of wood like logs. For the Sun, once the hydrogen starter fuel runs out, the fuel switches to burning those heavier logs (helium)! Just like a roaring fire, burning the heavier fuel makes the Sun hotter on the inside, causing it to swell into a massive Red Giant star.

Once the Sun becomes a Red Giant, it will grow so big that it gobbles up Mercury, Venus and maybe even Earth. The Sun will continue creating heavier elements for fuel until its core is filled with carbon, and it grows huge. During its absolute biggest phase, which Astronomers call the Asymptotic Giant Branch, the Sun's surface may even reach the orbit of Mars.

Mars will then turn into a hot, lifeless desert of molten rock. Luckily, the outer planets like Jupiter, Saturn, Uranus, and Neptune are safe. The Sun's changes will cause the giant planets to drift into larger orbits, becoming even colder than they are today.

When will the sun burn out?

At that point, the Sun cannot continue to grow or burn. The Sun does not have enough mass or power to burn carbon, so it has finally run out of fuel. At this point, the outer layers of the Sun will float away into space like colorful puffs of smoke, forming a glowing cloud known as a Planetary Nebula. Contrary to the name, a planetary nebula does not create planets.

Just like the embers left at the end of campfire fire, the Sun leaves behind its hot and glowing core. These embers will slowly cool off for trillions (1,000,000,000,000) of years! Scientists call this final stage a White Dwarf.

For more info and activities…

For kids space games, videos, crafts and more, visit:

• NASA Kids
• NASA Sun Facts

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