The Importance of Studying Exoplanets
Jesse Short
4/30/17

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The Importance of Studying Exoplanets
Discussion of extraterrestrial planetary bodies is thousands of years old, but it was not until the 1990s that the chance discovery of an exoplanet spurred the establishment of organizations dedicated to searching for and detecting exoplanets.1 Since then, thousands of cosmic bodies have been identified as exoplanets, many of which are potentially suitable for life.1 Most of the first exoplanets discovered were gigantic gaseous planets like Jupiter, but recent discoveries from the Kepler Telescope have elucidated numerous planets similar to Earth in terms of geography and size.2
What Are Exoplanets?
Exoplanets are planetary bodies located outside …show more content…
First, the true mass of the body—regardless of formation—must be less than 13 times the mass of Jupiter.1 Most of the currently confirmed exoplanets are larger than Earth, falling within the category known as
‘Super-Earths’ which are between the size of Earth and Neptune.4 This does not mean, though, that exoplanets are only ever larger than Earth; rather, insufficient detection technologies have demonstrated difficulty identifying smaller cosmic bodies.4 Second, the body cannot throughout its lifetime sustain thermonuclear fusion in its core.1 Cosmic bodies above these cut-off points are termed ‘brown dwarfs’.1 Third, the cosmic body must orbit a star or stellar remnant and not be free-floating as these bodies are termed ‘sub-brown dwarfs’ rather than planets.1 Fourth, the body must ‘behave’ like a planet in that it follows an elliptical path of orbit arounds its sun and is bound by gravity.1

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Despite the immense focus of the last several decades toward detecting and …show more content…
atmosphere) is conducted similarly, apart from the limited breadth of evaluation for exoplanets due to the distance from Earth.1
How Many Exoplanets Exist?
According to astronomers working as part of NASA’s Kepler Mission, 4,496 cosmic bodies are candidates for exoplanet status, 2,331 of which have been confirmed to demonstrate characteristics defining an exoplanet.4 Statistically speaking, though, it is estimated that there is an exoplanet for every star in the galaxy which comes out to roughly one trillion potential exoplanets.2 Of those already confirmed by NASA, though, only 21 are in the ‘habitable zone’.5
The ‘habitable zone’ is the distance between a cosmic body and its sun within which a planet could sustain life.1 This is also sometimes termed the ‘Goldilocks zone’ because it is neither too hot nor too cold. Planets are habitable if they are terrestrial (i.e. have a rocky surface) and can sustain liquid surface water.1 As Seager acknowledges, this definition is based on the assumption that extraterrestrial beings would—as we do—require water to sustain life, but as no extraterrestrial life has yet been found, this definition is incomplete.1
The first confirmed exoplanet was a gaseous cosmic body termed 51 Pegasi b.2