Other Worlds: Extra-Solar Planets

Over the centuries, our ideas of the universe have come a very long way. In 1610, moons were discovered by Galileo to orbit other worlds, which helped to spread the idea of a sun-centered solar system. In 1801, the first asteroid found was by Piazzi, which helped erase the idea of a "clean" solar system of a star, planets, and moons. And it was less than a century ago in 1923, other galaxies realized by Hubble, which helped to launch modern views of the Universe.

However, despite the discoveries over the centuries, we still had no idea until 1995 if our solar system was a fluke: Were there other planets out there circling other suns? In 1995, the perhaps not-so-startling discovery of an extra-solar planet circling the star 51 Peg was made. Since then, the number of known extra-solar planets has ballooned to over 150 and is still rising.

Dedicated surveys have been launched in the intervening years, and NASA plans on launching a Terrestrial Planet Finder space craft that will search for Earth-like planets around other stars. This is a very cutting-edge field of astronomy, and every new discovery maintains the possibility of revolutionizing the field.

"Extra-solar planet" is a long phrase to say. In recent years, it has been shortened to "exoplanet," which is what the rest of this section will use.

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