Dear Kristen,

Our sun is really one big star. And there are billions and billions of stars in our universe.

“More than we can even count,” added my friend Phil Lou. He’s an expert on solar energy here at Washington State University. He’s really curious about finding ways to power homes and schools using energy from the sun.

“Most of the energy and life around us that we know is linked to the sun,” he explained. Then we put on our sunglasses, slathered on some sunscreen, and headed out to explore.

Screen Shot 2016-05-06 at 4.08.12 PMAs we walked along, we spotted some grass and plants. Lou pointed out that plants use energy from the sun to help make their own food. A leftover from this process is the oxygen that we breathe.

Humans can also get energy when they eat plants—or eat the animals that once ate the plants. The sun also puts energy into the oceans and evaporates water, which helps keep water moving through the planet. The sun heats land and air which causes wind and weather. All this energy from the sun is really important to support life on Earth, Lou explained.

“It also makes Hawaii and Fiji great places to go,” he added. It sometimes makes for nice sunny catnaps here where I live in Washington state, too.

Even the oil, coal, and gas we get from the ground and use to power cars and make electricity started with energy from the sun. These kinds of fuels came from old decomposing animals and plants—animals and plants that got their energy from the sun’s rays.



Stars, like the sun, can come in all kinds of colors, shapes, and sizes, too. Scientists put them in different categories depending on their size, brightness, and other characteristics. According to these rules, the sun falls into the category of a yellow star.

Scientists have also calculated that it’s about 27 million degrees Fahrenheit inside the sun’s core and more than 9,000 degrees Fahrenheit on its surface. Thankfully, we are 93 million miles away, so we get just the right amount of warmth and energy from it.

Although our sun might be the closest star to us on Earth, it certainly is not the biggest or brightest star in the universe.

“Our sun is fairly puny compared to some other stars,” Lou said.

In fact, if you put our sun next to the giant star VY Canis Majoris, you could barely see it. It’s a speck, like a grain of sand next to a basketball. Consider the fact that you could fit a million Earths in our sun and you can start to realize just how big some stars can get. We are still learning about different stars and if there might be more sun-like stars out in our universe.

“It gives us something to really ponder,” Lou said. “Isn’t that great?”

We would love to hear more questions from you about solar energy and how it works, too. Or send us your own ideas about how to use energy from the sun to power our world. Write to Dr. Universe at


Dr. Universe