For hundreds of years, astronomers believed that our sun was the only star in the universe with planets. As strange as that sounds today, scientists felt that the conditions which predicated the existence of planets only existed in our own solar system. In fact, the idea of planetary exploration was so preposterous in science that few astronomers or physicists were willing to risk their careers in this endeavor. As late as the early 1990s, planetary exploration was not considered a serious area of study. But that changed forever with a shocking discovery in 1995.
51 Pegasi b
According to nationalgeographic.com, Michel Mayor and Didier Queloz discovered a planet orbiting a star outside of our solar system in 1995. The planet was named 51 Pegasi b because it orbits the star 51 Pegasi. The planet is extremely large, yet is located even closer to its star than Mercury is to the sun. Almost overnight, the study of planetary exploration exploded on the scientific scene. Numerous other planets were discovered in just a few years. But the main question being asked was whether or not any of these planets could support life.
Initially, the detection methods used in planetary exploration were primitive. Hence, most of the planets being discovered were extremely large and very close to their sun. This led to them being called hot Jupiters. As astronomers continued to find fault with the discovered planets, they noted a humorous parallel to the famous fairy tale “Goldilocks and the Three Bears” that led to the phrase Goldilocks Zone.
The Goldilocks Zone
In the story, Goldilocks finds fault with the porridge, the chairs and the beds. Everything is too hot, too cold, too big, too small, too hard or too soft. Finally, she finds one that is just right. Therefore, scientists working in planetary exploration say that a planet that is not too small, not too big, not too hot and not too cold exists in the Goldilocks Zone. More simply put, a planet that is in the Goldilocks Zone is said to be habitable (by our standards.)
According to Nicole Gugliucci, the most likely candidate for a planet lying in the Goldilocks Zone may be Gliese 581 g. Discovered in 2010, there is still a high level of disagreement among astronomers as to whether this planet is within the Goldilocks Zone and whether it even exists. Another planet in that system, Gliese 581 d, may be in the Goldilocks Zone because although it is considered too far from its sun, its large mass may hold an atmosphere dense enough to support life. Regardless of the viability of the Gliese 581 planets, the explosion of planetary exploration research makes it a virtual certainty that a number of planets in the Goldilocks Zone will soon be found.
“Alien Earths,” nationalgeographic.com
Nicole Gugliucci, “Gliese 581g and the Nature of Science,” discovery.com
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