Seven Wonders beyond the Solar System

Seven Wonders beyond the Solar System — page 3 — 1 The Tarantula NEBULA The Tarantula Nebula is a birthplace for new stars

Seven Wonders beyond the Solar System — page 4 — STARS ARE HUGE BALLS OF GAS IN SPACE THAT GIVE OFF LIGHT HEAT AND OTHER KINDS OF ENERGY THE SUN BELOW IS A STAR THE UNIVERSE CONTAINS BILLIONS AND BILLIONS OF STARS Like people stars are born Unlike people stars are born inside clouds The clouds that give birth to stars are vast areas of dust gas and ice in space Most of the gas is hydrogen The universe is filled with millions of such clouds Some are small and some are enormous These clouds are called nebulae Nebula referring to only one cloud means cloud in Latin The Tarantula Nebula is the biggest nebula anyone knows about It is trillions of miles wide

Seven Wonders beyond the Solar System — page 5 — THE SEEDS OF A STAR All substances including the gases inside nebulae are made of tiny particles Some of the smallest particles are called atoms Groups of atoms are called molecules Inside a nebula molecules are spread very far apart But the molecules have gravity the force by which one substance attracts another So the molecules inside a nebula attract one another They start to drift together The nebula begins to contract or shrink The contraction begins where the gas and the dust are a bit denser than elsewhere in the nebula Once the contraction starts it cannot stop Molecules of dust and gas start drifting toward the center of the nebula which has more material and therefore more gravity As the gravity increases more particles come together The molecules bump against one another Every time this happens a little heat is created As the nebula continues to contract its molecules continue to move closer together More and more molecules bump against one another The nebula grows even warmer Eventually the dust and the gas start sticking together in a lump The lump grows larger and larger This lump of contracting gas and dust is just a very small part of a much larger nebula Other small knots of contracting gas and dust might also be SEE FOR Yourself Gases grow hotter when they are compressed or squeezed together You can see this process for yourself by inflating a bicycle tire As you press more air a gas into the small space of the tire you'll feel the tire get hotter The same heating occurs when gases squeeze together inside a nebula Nebulae glow with light from new young stars

Seven Wonders beyond the Solar System — page 6 — Nothing else can be so pretty A cluster of vapor the cream of the milky way a sort of celestial cheese churned into light Benjamin Disraeli British political leader remarking on the creation of a star 1847 forming at other places in the nebula The small knots might eventually become stars A STAR IS BORN At the center of the nebula the gas and the dust become very dense or tightly packed together The center grows hotter as more and more gas and dust fall into it As more material falls in the gravity at the center of the nebula grows greater The more gravity the nebula has the more tightly packed the material becomes In just one year a nebula can shrink to one ten thousandth of its original size Soon the nebula reaches 3,000°F 1,650°C This is hot enough to vaporize or turn into gas any grains of ice or dust the nebula contains The densely packed nebula begins to glow dim red like a hot coal As the core of the nebula continues to heat up the nucleus center of each hydrogen atom presses against the one next to it The atoms fuse or stick together like two balls of clay being squished together When hydrogen atoms fuse the hydrogen turns into a different kind of gas helium The process of hydrogen becoming helium is called nuclear fusion This process creates vast amounts of energy Fusion is not easy to achieve It requires tremendous pressure and a very high HIGH Power Fusion creates huge amounts of energy Every 2.2 pounds 1 kilogram of hydrogen that turns into helium inside a star creates about 400 trillion trillion watts of energy That's enough energy to light 10 trillion trillion 40 watt lightbulbs The Tarantula Nebula

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