This image shows colliding galaxies.
Click on image for full size
NASA is involved in projects which are designed to find planets outside the solar system. So far about a dozen planets have been found! These are quite large planets, about the size of the planet Jupiter, and probably made of gas, just as Jupiter is. Scientists hope one day to find planets the size of Earth (terrestrial planets).
To read more about terrestrial planets like the Earth, and gas-giant planets such as Jupiter, you can leave the tour and read more about the Earth and Jupiter.
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Shop Windows to the Universe Science Store!
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are also full of classroom activities on different topics in Earth and space science!