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Burning questions about the sun? Check out these five facts

Sunlight shining through the canopies in a line of trees.
(Photo via Shutterstock)

The sun is the center of everything, and that's not just something we say to show how important it is. The sun is quite literally in the center of our solar system, and everything else — planets, comets, asteroids, even space garbage — revolves around it. The sun is what keeps everything in its place.

The sun is itself a star, one of about 100 billion in the Milky Way galaxy, but it's an extremely important one for all the living things on Earth. Without it, we — and all other living things — would cease to exist, National Geographic reports. We have the sun to thank for the seasons and ocean currents, and it also influences the weather. 

We learn at a very young age how important the sun is to the health of our planet and even ourselves. But that's about where the education ends for most us. But we've got some burningly interesting facts to share about the sun to round out your knowledge.

It's our nearest star neighbor

The sun is a star, and it's the closest star to Earth, according to NASA. Of course, close is a relative term, and even though it's our closest star neighbor it's really nowhere near Earth. It's more than 93 million miles away from our home planet. Let's compare that to Venus, our closest planetary neighbor. When Earth and Venus are at their closest point to each other, they are about 38 million miles apart, much closer to us than the sun. Earth and Venus are usually much farther away from one another than 38 million miles, however. In fact, many times Mercury is closer to us on Earth than Venus. 

If you think back to your elementary school science class, you might recall a mnemonic device you learned to help you remember the planets in the order they are in the solar system. Maybe the sentence "My (Mercury) very (Venus) educated (Earth) mother (Mars) just (Jupiter) served (Saturn) us (Uranus) nine (Neptune) pizzas (Pluto)" rings a bell? Of course, kids today have to learn a new phrase, because Pluto was demoted to dwarf planet status in 2006. No matter how you remember the order of planets, what you're remembering is the order of how close the planets are to the sun. Mercury is closest, about 35 million miles from the sun, and Neptune is the farthest, more than 2.7 billion miles away. And for old time's sake, let's not forget about Pluto, which is 3.7 billion miles from the sun.

So how long would it take to travel to the sun? On a plane flying 550 mph, it would take 19 years. But a spacecraft can fly much faster than a plane. Consider that NASA's Mars Curiosity rover took between eight and nine months to reach the red planet, traveling at about 8,400 mph. At that speed, it would take a little more than 15 months to reach the sun.

It's got a lot of star power

Not only is the sun the closest star to Earth, it's the only star in our entire solar system. It's also the largest object in the solar system, so large that you could fit 1.3 million Earths inside it, NASA reports. Put another way, the sun is 100 times as wide as Earth and 10 times as wide as Jupiter, the largest planet in our solar system. And you would need more than 330,000 planets the size of Earth to equal the mass of the sun. 

And you know the sun is hot, but do you know just how hot it is? At its core, temperatures reach about 27 million degrees Fahrenheit, which is hot enough to sustain nuclear fusion, NASA reports. All that heat is essential because it creates the pressure needed to support its mass. Without that pressure, the sun would collapse on itself. 

You know that saying "as hot as the surface of the sun"? While it certainly may be a good way to get your point across about how hot something is, it's a little bit of a misnomer because the sun doesn't actually have a surface. Instead, it's a giant ball of plasma. What we perceive to be the "surface" of the sun is a photosphere, which is sort of like an envelope around a star from which the light and heat radiate.

It won't last forever

All good things must come to an end, and the sun won't shine forever either. It's been burning bright for more than 4.5 billion years, but eventually it will burn out when it runs out of fuel, according to NASA.

The sun burns hydrogen for fuel, and lots of it — several hundred million tons every second, according to Live Science. Lucky for us, there's plenty of hydrogen left in the sun. Experts believe the sun has enough fuel to burn bright for another 5 billion years.

When the sun runs out of hydrogen in its core, it can no longer support itself. It will continue to burn the hydrogen around the core and expand into a red giant star, NASA reports. When this happens, it will completely engulf Mercury and Venus — the two planets closest to the sun — and will likely engulf Earth as well. At the same time, the sun will begin burning all the helium it contains, a process that may take 100 million more years. At this stage, it is considered a red supergiant. As time goes on, the sun will lose its mass, eventually leaving behind a carbon core. Once the carbon core cools, the sun will be a white dwarf, which is the remnant of a star.

It's not that big by star standards

The sun is the biggest, brightest object in our solar system, but among the billions of stars in the Milky Way galaxy it's just average, classified as a medium-sized star, according to Space.com. There are stars out there that are much bigger than the sun, much, much bigger.

Consider the star called Betelgeuse. It's 700 times larger than the sun, and 14,000 times brighter, Space.com reports. The largest known star so far is one called UY Scuti, which has a radius 1,700 times larger than the sun's. Can't fathom how big that is? Well, 5 billion stars the size of the sun could fit inside UY Scuti. Of course, if the sun is a medium-sized star, there must be plenty of smaller stars out there as well. Some stars are quite small by the sun's standard, only about a 10th of the size. 

It rotates just like the planets

All the planets in our solar system revolve around the sun, and they also all rotate on an axis. Each rotation is the length of a day, and each revolution around the sun amounts to a year. On Earth, a full rotation takes about 23 hours and 56 minutes, and a full revolution takes about 365.25 days, according to NASA. Different planets rotate and revolve at different speeds. On Venus, a day lasts 5,832 hours, while a day on Neptune lasts 16 hours. A year on Venus is 225 days, and a year on Neptune lasts 60,190 days. 

While all this rotating and revolving is taking place, the sun itself is rotating on its axis too. (It doesn't revolve, though, because it is the center of the solar system — the thing everything else revolves around.) Because the sun is not a solid object, it doesn't spin like Earth does. It spins faster at its equator than it does at its poles. At its equator, it takes the equivalent of 25 Earth days to complete a rotation, and on its poles one rotation takes 36 days.

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