Supernova from space (thanks to NASA and the Hubble Telescope) What is a supernova? Supernovas are exploding stars. Red giant stars explode when they have used up their hydrogen and helium fuel, and converted most of their atoms to iron atoms. A red giant star explodes Red giant stars have a lot of gravity pulling them inward. Normally they don't collapse inward because the nuclear [...]
The Eagle Nebula Stars don't last forever, though they do last for billions of years. And they don't stay the same throughout their existence - they change over time. The earliest beginning of a star is called a nebula. A nebula is a cloud of hydrogen and a few helium atoms hanging in space. Sometimes a nebula just [...]
What are planets? The planet Venus from space Before there were planets For several hundred million years after the Big Bang, there were no planets, only stars. Planets couldn't form until the first stars ran out of fuel and exploded into supernovas, about 14 billion years ago. The supernovas spewed out thousands of tons of carbon, oxygen, iron and other elements into space. Planets [...]
The Eagle Nebula A nebula is a bunch of atoms and molecules floating in outer space, like a cloud of dust. More than one nebula are called nebulae, because -ae is the plural ending in Latin, just as -s is the plural ending in English. Nebula is the Latin word for a cloud. The earliest nebulae formed just [...]
The galaxy M 100, seen through the Hubble telescope What is a galaxy? A galaxy is a group of millions of stars that are relatively near each other. Most stars seem to be in one or another galaxy. Earth's own star, the Sun, is in the Milky Way galaxy. What is the sun made of? What are [...]
Earth from space: How old is the Earth? When did the Earth form? Like Mercury and Venus and the other planets that go around the Sun, the Earth probably formed a little more than four and a half billion years ago. (That's about 4,600,000,000 years ago.) What's the sun made of? How do planets form? All our physics articles What [...]
A comet in the night sky What are comets made of? Comets are balls of leftover rock and ice in space. They started out when a star exploded into a supernova. What is a supernova? More about ice All our space articles When were the first comets? A nebula formed, and then most of the material in our nebula merged together, about [...]
