In about 5 billion years, the Sun will die an amazing death.
As its hydrogen runs out, the Sun will start to burn helium. It will grow into a red giant star so big that it reaches Venus’s orbit. Once the helium is used up, the Sun will collapse. It will become a hot white dwarf star about the size of Earth. Then it will cool.
We know all this from watching other stars. Point a telescope in almost any direction. You’ll see a star’s birth or death in progress. Recently, scientists have found that some stars have planets spinning around them, just as our star does. Maybe somewhere, there’s a planet where creatures are wondering, “Who’s out there?”

Supernovas
▲ The fireworks around the Sun’s death will be small, compared to what happens when a larger star dies. When a massive star runs out of fuel, it explodes. This turns it into a supernova. For a few days, it’s as bright and hot as an entire galaxy. In 1054, Chinese astronomers saw a supernova. It was so bright, they could see it during the day.

Nebulas are clouds of gas, dust, and ice in space. They often form after supernova explosions. They become places where new stars form. Scientists believe the Sun is a recycled star. That’s because it contains heavy elements such as iron. These elements aren’t always found in live stars. This means the Sun was formed out of a gas cloud containing older stars that had died.


▲ Even if there is life somewhere else in the universe, we may never find it. Distances in space are so large that they’re measured in light-years. A light-year is the distance that light can travel in one Earth year. Light travels about 186,000 miles per second. That’s about 6 trillion miles per year. The closest star to our Sun is Proxima Centauri. It’s about 25 trillion miles away. The light we see from Proxima Centauri takes roughly four years to reach us. That means it’s about four light-years away.

◀ A lot of what we know about the universe began with Galileo Galilei (1564–1642). He was the first person to study the universe using a telescope. He also proved Copernicus’s theory: The Earth goes around the Sun, not the other way around. The Inquisition in Rome tried him for that. He spent the last eight years of his life under house arrest. As an old man, he went blind. This was partly because he’d stared at the Sun without eye protection.
Check It Out!
Where do stars go during the daytime?
They’re still in the sky. But the Sun is so bright we can’t see them.

Sun Fact
Rotation
27 days at equator, 30 days at poles. They differ because the Sun’s gases move at different speeds.
Pulsars
When a giant or supergiant star explodes, it does one of two things. If it collapses completely, it becomes a black hole. That’s a place where objects get sucked in, stretched to infinity, and trapped forever. Or it could become a pulsar. That’s a neutron star that spins very quickly. When pulsars were first discovered, their pulses of light seemed like messages from aliens. Scientists half-jokingly called them LGMs—Little Green Men. ▼

This is an X-ray view of the Crab Nebula. You can see a spinning pulsar at its center. This nebula is what’s left of the supernova the Chinese astronomers saw in 1054.
Here are three other views of the Crab Nebula.
