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September 12, 2010

'A Solar System Is Born'

June 21, 2012|By Diane K. Fisher
(ESA 2010 MPS for OSIRIS Team. )

Besides our one beautiful star, the sun, we have eight planets, several dwarf planets, dozens of moons, millions of asteroids, a trillion comets and — most important of all — us! We call it: our solar system. How did our solar system even get here? What were the ingredients that made the sun and all the planets and other objects?

How can we find out?

What if we could watch a video and see it all unfold again? When the video starts, we see a huge, wispy cloud of gas and dust swirling slowly throughout a huge region of space. Slowly, the clouds of gas and dust begin to shrink and thicken. Gravity causes the matter to grow closer and closer together. Eventually, the matter becomes a flat, spinning disk. The smaller and more compact the disk becomes, the faster it spins. The stuff at the center of the disk is the densest (most squished together). Gravity pulls everything inward. The dense center of the disk heats up as the energy of all the particles squeezes into a smaller and smaller space. Finally, the material at the center of the spinning disk is so dense and so hot that the atoms of gas fuse together and boom! Nuclear fusion begins! Huge amounts of energy blast forth. A star is born! Hooray! But the birth of the new star has eaten up almost all the material in the disk. Everything else in the solar system, including the planet to be named Earth, must be made of the leftovers.

The leftover particles collide and stick together. When these stuck-together pieces grow large enough, gravity goes to work pulling some of them together into small rocks and chunks of ice. After a few million years, many of the objects grow large enough to become planets and moons. Bringing us to the present.

Not all the materials were used in forming the planets and moon. Some materials remain as small, rocky objects called asteroids. There are millions of them that orbit in the asteroid belt between Mars and Jupiter. All of them piled together would be smaller than our moon. Farther out, beyond the orbit of Neptune, is another region of leftover icy objects called the Kuiper [KI-per] Belt. Pluto lives out there. Sometimes the gravity of a larger object flings one of these smaller objects toward the sun. These icy travelers become comets. As they get closer to the sun, they heat up. Gas, dust and ice boil off, giving the comet a long, wispy tail. How do we get close enough to these small, distant objects to study them?

We send smart, well-equipped detectives like the Rosetta spacecraft. Rosetta's final destination is Comet 67P/Churyumov-Gerasimenko. It will reach this comet in 2014. It will orbit the comet for two years and study how the comet changes as it gets closer and closer to the sun. Rosetta will also drop a small lander to study the nucleus (the solid core) of the comet up close. On the way to the comet, Rosetta has already studied a couple of asteroids up close. Recently (July 10, 2010), Rosetta took some amazing pictures of asteroid Lutetia and took measurements of many of the asteroid's features.

The European Space Agency manages Rosetta. NASA built several of the important scientific instruments. Rosetta will unlock the mysteries of the oldest building blocks of our solar system — the comets and asteroids. Rosetta will allow scientists to look back 4.6 billion years to the birth of our very special solar system.

Visit our solar system page on The Space Place, and play the Rosetta Comet Encounter mini-game. Go to and click on the comet.

This article was written by Diane K. Fisher and provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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