Seven Wonders beyond the Solar System

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

Seven Wonders beyond the Solar System — page 7 — temperature It takes 10 million years of contraction for a nebula to reach the temperature needed for fusion to begin As soon as the spark of fusion is lit the nebula stops contracting It becomes a full fledged sun It begins running on the energy produced by fusion A star has been bom THE BIGGEST STAR FACTORY If you live in the Southern Hemisphere southern half of Earth you can look into the sky at night and see the Tarantula Nebula It is the largest star nursery anyone knows about Hundreds and perhaps even thousands of new stars are being born within it Powerful telescopes in the Southern Hemisphere allow us to see the young stars inside the Tarantula Nebula

Seven Wonders beyond the Solar System — page 8 — The nebula looks a little like a tarantula a big hairy spider To the naked eye the Tarantula Nebula doesn't look like much It looks like a faint fuzzy blob of light in the constellation star group Dorado When seen through a telescope however the Tarantula Nebula looks like a swirling mass of red and green gases Its shape resembles a tarantula a large hairy spider A light year is the distance light travels in one year Light travels 186,000 miles 300,000 kilometers per second So 1 light year equals about 5.88 trillion miles 9.46 trillion km The Tarantula Nebula is 170,000 light years away from Earth So light from the Tarantula Nebula takes 170,000 years to reach Earth At the center of the Tarantula Nebula is a small cluster of young stars Energy from these stars makes the nebula glow brightly much like electricity passing through the tube of a neon sign makes the gas inside it glow The Tarantula Nebula

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