by Bob McDonald
When our sun reaches this stage of its life, that will be the end of the Earth and all life on it. The sun will completely fill our skies. Temperatures on Earth will quickly rise until the oceans boil into steam, forming thick clouds around the whole planet. The heat of the big sun will burn these clouds off into space, giving the Earth a long, white tail like a comet. As the hot gases from the swollen sun surround the Earth, mountains will melt into valleys until the whole planet turns into a molten ball of boiling rock that will eventually become a burned-out cinder inside a dying star.
But let’s look at the upside: with one final dying gasp, the sun will blow off its outer layers, along with the debris from what was our solar system, all of which will drift off into space, forming a brand-new nebula. From the death of stars comes the life of new stars and planets.
If you’ve ever wondered what happens to stars when they stop shining, touch your face. We are made of stardust. Today we live, but one day we will die. The atoms in our body will be incorporated into the ground, and then, a long time from now, the Earth and everything on it will be vaporized and cast out into space, where parts of it will reform into beautiful nebulae.
Who knows? Perhaps one day, way in the future, the atoms that make up your body will become part of a planet going around a new star. Maybe life will evolve on that planet and one of those life-forms will look up into the night sky and wonder where it all came from.
ON THE DRAWING BOARD
Here’s a wild idea: we might someday build a spaceship called the interstellar ramjet that uses clouds in space as rocket fuel. It would be a very large ship sent far away to other star systems. If the journey involved passing through a giant hydrogen cloud, the ship would extend an enormous invisible scoop made of a magnetic field. The field would gather up some of the gas floating in space and funnel it into the ship’s engines. There, the hydrogen would be burned and blown out the back end of the ship, making it go faster. A ship like this could theoretically go faster than any vehicle ever made, cutting down the travel time to the stars. There’s just one little problem we still have to solve: Once you get a ship this large traveling that fast, how do you stop it?
To a faraway alien astronomer four billion years from now, our sun’s nebula will probably look like a ring or a shell. That’s because our sun is a fairly average-sized star. But there are giant stars out there, much bigger than our sun, and when they die, they go out with a bang called a supernova.
Supernovas are so violent and hot, they act like giant blast furnaces, forging heavy elements like nickel and gold. Think about that. When you see a gold ring or any piece of gold jewelry, you’re looking at an element that was made not by the Earth but inside a dying star during a supernova explosion billions of years ago.
You can see an awe-inspiring nebula with your own eyes. All you need to do is find the constellation Orion. Orion comes around every winter and is the most easily recognized star pattern after the Big Dipper. The three stars in a row are the belt. Hanging from it is a sword marked by three more stars pointing downward. With binoculars, you’ll see that the middle point of the sword looks a bit fuzzy. The misty part isn’t actually a star but a nebula. This gigantic cloud, almost 1,500 light-years from Earth, is a cosmic nursery containing hundreds of stars still in the process of forming, plus other stars already born. Four of them, together known as the Trapezium, are baby suns that flared to life less than a million years ago. The intensely hot Trapezium stars are what make the Orion Nebula glow.
4 What Is Dark Matter?
Space seems to be mostly empty and dark. At least, that’s how we thought about it for a long time. But now astronomers think something is hiding in the darkness. It’s everywhere, it’s powerful, and no one knows what it is.
They call it dark matter. And when scientists say “dark,” that really means, “We don’t know, but we’re working on it.”
The first clue that there’s something out there in the darkness came from watching how things move in space. Almost everything in space moves in circles. Planets go around stars. Stars clump together and swirl around in galaxies, and galaxy clusters spin around one another like bugs flying around a light.
About eighty years ago, though, an astronomer named Fritz Zwicky discovered an anomaly. He was studying a group of about a thousand galaxies known as the Coma Cluster. He wanted to know just how much gravity it took to hold that particular cluster together. Gravity comes from mass, and when Dr. Zwicky calculated the mass of all the galaxies, something didn’t add up. The galaxies simply didn’t have enough mass by themselves to produce enough gravity to hold the group together. Those galaxies should have been flying away from one another!
So what was holding them together? Dr. Zwicky figured there had to be something else in that cluster that he couldn’t see, some sort of invisible mass that was producing extra gravity. And the astounding part was that there seemed to be more of that mystery material in the galaxies than there were stars.
Scientists aren’t very good at naming things. Whatever was holding everything together was invisible—or dark. And since it was something, it might be matter. So “dark matter” is what it was called.
But how do you study something invisible? Astronomers have found galaxies in space that have been bent out of shape or stretched into long, thin arcs that look like eyebrows. The light from those distant galaxies is distorted by invisible dark matter that lies between us and those galaxies. So even though dark matter is invisible, it gives itself away by distorting light.
Scientists think dark matter could be made of invisible particles that are so small they pass right through the Earth, the same way light (which is also made of waves of particles) goes through a window. Scientists have found some invisible particles in space called neutrinos. They come from the sun and other stars in the galaxy. But there are not enough neutrinos in the universe for them alone to make up all dark matter. There must be something else.
SPACE PLACES
We can study neutrinos, but it’s a tricky process. To capture something that travels right through the Earth, you have to go inside the Earth, which isn’t easy. Deep underground in northern Ontario is the Sudbury Neutrino Observatory. It uses a big ball filled with a special clear liquid, called heavy water, that is used inside nuclear reactors. The atoms in this water give off a tiny flash of light if a neutrino hits them. The observatory saw enough flashes to prove that neutrinos exist. Many neutrinos come from the sun, which means they shine down on your head during the day. But since they pass right through the Earth, they also shine up under your feet at night! Now scientists in the same underground lab can further study the nature of these ghostly particles and are starting to look for others that might be dark matter.
Some scientists think that the answer lies in massive particles that are invisible but not very strong. They call them WIMPs—Weakly Interacting Massive Particles—because they don’t bother interacting with ordinary matter like the stuff you and I are made of.
When you drop a ball on a table, it bounces. That’s an example of interaction. The ball and the table push against each other. But if you drop a WIMP on the table, it won’t bounce. It will pass right through the table. Then it will continue through the floor, through the Earth, and out the other side into space. So even though a WIMP has more mass than a neutrino, it passes through solid matter as if it weren’t there. Remember, this is just a theory. Nobody has actually spotted one of these strange subatomic particles—yet.
If all the dark matter we’re looking for is made of WIMPs, this answers the mystery of what keeps the universe in balance. But if there’s something else out there, we have yet to find it.
Consider this: when you’re outside on a clear, starry night, the blackness you see is what most of the universe is made of. No one knows exactly what that dark stuff is, but it is believed to make up 95 percent of the universe. What constitutes the rest? Galaxies, stars, planets—and us.
5 Why Is the Sun So Hot?
The sun is hot because it is incredibly big. If the sun were a beach ball, the Earth, by comparison, would be the size of a pea.
The sun weighs a billion, billion, billion tons—two quintillion kilograms (yes, that’s a real number). When an object is that big, even if it’s made entirely of gas, its weight squeezes everything together incredibly tightly. And when matter is squeezed together under such enormous pressure, it gets hot—up to fifteen million degrees Celsius, in fact. That’s plenty hot enough for the sun’s gases to turn into a hot plasma.
A plasma is a glowing, electrified gas, like the white hot flash of a lightning bolt. The flame in fire or the glow in neon lights are other examples. But none of these are as hot as the plasma at the center of the sun. Atoms in the sun’s plasma fly around in all directions, sometimes smashing into one another at high speed and fusing together to make bigger atoms. This is similar to the way two water drops might join together in a rain cloud to become a larger one. In the case of plasma, this process of fusion gives off a lot of heat and light, which is the energy that makes the sun shine.
ON THE DRAWING BOARD
Scientists on Earth would like to duplicate the fusion happening in the sun so everyone in the future has lots of clean energy. But replicating the process is hard to do because when you heat up plasma to fifteen million degrees, it melts whatever container you put it in. We’ve managed to create fusion, but only for a second or so inside a nuclear bomb, which is the most powerful bomb there is.
There is a less destructive way to duplicate the sun on Earth, though. The world’s largest fusion reactor is under construction in France. It’s called ITER, which is Latin for “The Way.” It plans to use a donut-shaped chamber to heat a form of hydrogen up to 150 million degrees Celsius, ten times hotter than the center of the sun. All that heat from the fusion will warm up liquids in the walls of the reactor, until that liquid turns to steam that will be used to run generators and make electricity.
The biggest challenge with ITER is that it will require a huge amount of energy to heat the hydrogen plasma up to that temperature. And it will take still more energy to run the powerful magnets needed to keep the plasma floating in the center of the donut without actually touching the walls. Scientists hope that the fusion reactions will eventually sustain themselves the way they do in the center of the sun, producing more energy than what is needed to run the machine. If they succeed, then fusion reactors may provide clean energy for the future.
In a sense, the sun is a big bomb that never stops exploding. So why doesn’t the sun blow itself to pieces?
Because it’s big.
There is a battle between two forces: the endless explosions in the center pushing out and gravity pulling everything back in. Neither force wins. The two balance each other out and the sun continues to shine brightly in our skies.
In case you’re worried that the sun will run out of fuel, know that the sun has so much gas that it will keep burning for at least another four billion years. So don’t worry: it will be there at sunrise tomorrow morning.
THE FUTURE IS NOW
Out in space, when sunlight reflects off an object, it pushes. The push is very tiny, and you wouldn’t feel it on your body, but if you had a mirror large and light enough, you could capture the pressure to sail around the solar system, all for free! The biggest challenge would be building a sail large enough to harness the solar energy. The sail would have to be at least a kilometer across to capture enough energy. Making a sail that large work on Earth would be impossible, but in space, everything is weightless. You could make the sail out of thin, shiny plastic—similar to the plastic used in potato chip bags—fold it into a small package, and launch it into space on a rocket. Then it would unfurl like a flower and take your ship to the moon or Mars purely on the power of sunlight. Imagine a future when solar sailors ride sunbeams to far-off planets.
If you could somehow get yourself to the surface of the sun and not be burned up by the scorching temperatures (the sun is cooler on the outside—only 6,000 degrees Celsius), you would not be able to stand up because the sun’s gravity is twenty-eight times stronger than what we feel on Earth. A person weighing sixty kilograms on Earth would weigh 1,680 kilograms on the sun.
I hope this convinces you not to go walking on the sun any time soon. You can always admire the sun by looking at it—just not with the naked eye. Scientists examine the sun using solar telescopes, which have special filters that stop most of the sunlight from getting into the sensitive instruments. One kind of solar telescope—the world’s largest, in fact—uses only a mirror.
The McMath-Pierce telescope in Arizona reflects sunlight down a long tunnel that’s filled with spectrographs—which analyze the sunlight—and mirrors, which capture the image of the sun’s surface on a big white screen near the bottom. The image of the sun on that screen is still so bright that scientists viewing it need to wear special goggles.
So what is it they see? The sun’s face is covered with black spots called sunspots. Most of those spots are larger than the entire Earth and are evidence of the violent activity taking place inside the sun. Scientists watch as the spots grow, hang around for a while, then disappear, only to return again in the course of an eleven-year cycle.
Scientists believe sunspots are formed when different parts of the sun swirl around one another. Because the sun is made of gas, it rotates faster at the equator than it does at the poles. That difference causes the magnetic field of the sun to twist. In some areas, the magnetic field breaks through the surface, reaches into space, and curves back down again. Enormous arcs of hot gas, so big you could pass the Earth underneath them, follow these magnetic lines, connecting the sunspots, which lie at the ends of the arch like pots of gold at the ends of a rainbow.
Sometimes these arches grow so big and tall that they snap, sending gigantic blobs of the sun’s plasma into space at more than one million kilometers per hour. Those projectiles are called coronal mass ejections, and every once in a while one of these blobs heads toward the Earth. They’ve been known to knock out satellites and cause power failures.
If an eruption happens on the sun, scientists send a warning so that companies with sensitive electrical systems can get ready. It’s a new kind of space weather forecasting.
We don’t have to fear these eruptions much. While they can affect our technology, they don’t hurt people because our atmosphere protects us. In fact, we get to see the effects in that beautiful light show called the aurora borealis (or aurora australis in Australia). The particles from the sun hit our air and make it glow the way electricity lights up the gases in neon signs. So if you’re fortunate enough to see the northern lights, you’re actually seeing a rain of light from space. You’re seeing a part of the sun hitting the Earth!
YOU TRY IT! Solar Telescope
WHAT YOU NEED
One pair of binoculars
One sheet of white paper
WHAT TO DO
Turn your back to the sun. (NEVER LOOK AT THE SUN THROUGH BINOCULARS! YOU’LL BE BLINDED INSTANTLY.)
Hold the binoculars on your shoulder with the large end facing the sun.
Hold the paper in front of you until you see the shadow of the binoculars on the paper.
4.Move the binoculars around until two bright spots appear on the paper. While holding them as steady as you can, turn the focus on the binoculars until the circles become sharp. You should see two images of the sun. Can you see any little black spots?
5.You’ll probably see the image shake a lot, which is actually the movement of your body. You can make the image steady by propping the binoculars up on the edge of a table or a pile of rocks instead of your shoulder.
6.You are now looking at the face of the sun.
The little black dots will look small to your eye. In fact, they may be hard to see at all. But remember that you could drop the entire Earth into each one of those dots. The sun is unimaginably huge!
6 Do UFOs Really Exist?
They’re objects moving in the night sky, and most times, you don’t know what they’re doing up there. They’re unidentified flying objects—UFOs—and they’re very real. But that doesn’t mean they’re alien spaceships.
Usually, we’re able to figure out what an object in the sky is. What we might think is a UFO often turns out to be an airliner or a satellite or the International Space Station. Once a UFO is identified, it becomes an IFO—identified flying object.
IFOs are common, of course, but that doesn’t stop many people from believing that what they glimpse is something else entirely. If all you see is a light in the sky, how do you know for sure what it is or isn’t? The idea that alien spaceships could be visiting Earth is not that unreasonable. When you think about the thousands of millions of planets that could be out there orbiting stars just like our sun, the chances are pretty good that some of those planets have life. And if some of that life is intelligent enough to build spaceships, maybe those life-forms would come to visit us. After all, we also strive to explore other worlds.
The idea of UFOs began in Roswell, New Mexico. In 1947, something was found about one hundred kilometers northwest of the city. Rancher Mac Brazel went to check his livestock following a massive thunderstorm. He came across an extensive area of debris the likes of which he’d never seen before. He gathered it all up and brought it to the sheriff’s office. The sheriff didn’t know what it was. Military gear, maybe? At the time, Roswell was home to the Roswell Army Airfield, the only atomic bomb base in the world. The sheriff called in one of the base’s intelligence officers, Major Jesse Marcel, who gathered up all the debris, loaded it on an aircraft, and took it away to a secret base called Area 51.