Exoplanets. Science fiction writers have assumed that other stars had planet from almost the beginning. However, it wasn’t until 1988 that Canadian astronomers Bruce Campbell, G. A. H. Walker, and Stephenson Yang published a paper about their discovery. That was fifteen years after the first Star Wars movie.
Since then, the entire subject of exoplanets has exploded. There are 1931 planets in 1222 planetary systems including 484 multiple planetary systems as of 14 June 2015. And some of those exoplanets are far stranger that science fiction writers imagining.
Consider Kepler-16b. This planet with a mass of about 1/3 of Jupiter orbits a binary star system. From its surface you could see two suns in the sky.
Kepler-11 has six planets orbiting in circles smaller than Venus’ orbit. Furthermore five of those planets are even closer to their parent star than Mercury is to our sun. Crowded. This stellar system could force revisions to the current theories about planet creation.
The term Hot Jupiter refers to Jupiter sized planets so close to their star that their year can be measured in days or hours.
Some of the Jupiter sized planets are significantly larger than you would expect. The largest to date is twenty-nine times larger than Jupiter. Is that a planet or a brown dwarf star?
What about a planet that is entirely made of water? It’s possible.
The impact of these discoveries to modern thought particularly touches on two viewpoints. One is the ‘rare earth theory’, which posits that the planet Earth is a unique combination of conditions. The other is Fermi’s Paradox. In 1950 Fermi commented on the size of the universe and exclaimed “Where are they?” Two different sides to the same question about the rest of the universe.
In November 2013 astronomers estimated that 22±8% of Sun-like stars have an Earth-sized planet in the habitable zone. Assuming 200 billion stars in the Milky Way, that would be 11 billion potentially habitable Earths, rising to 40 billion if red dwarfs are included.
40 billion! Imagine that.
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