Exoplanet

Exoplanets are planets outside of our solar system. Exoplanetary systems comprise of an exoplanet and a companion star. Exoplanetary systems vary greatly in terms of sizes and orbits. Exoplanets have been found using the transit technique on data collected by NASA’s Kepler spacecraft. They are found by collecting brightness data on stars and looking for periodic drops in brightness which would likely occur when an exoplanet blocks the star (Howell, 2015). The first exoplanet orbiting a star was found in 1995, merely over two decades ago. The possibility of the existence of another solar system, especially one like the earth and sun, was unrealistic at the time (Dunbar, 2015). NASA, along with various other organizations from all over the world, are searching for an exoplanetary system where there is a planet that is the same size as planet Earth, and is orbiting a sun-like star in the habitable zone (Howell, 2015). Over the years, this search has shown hope for a real exoplanetary system duplicating the Earth and the sun. Twelve of the new planets discovered using the Kepler spacecraft orbit in their star’s habitable zone. Of these, nine orbit stars are similar to the sun in terms of size and temperature (Kepler and K2, 2015). This essay discusses, Kepler-425b, the most Earth-like exoplanetary system known to planet Earth, to date.

Kepler-452b is an exoplanetary system which most closely resembles our solar system. It is commonly referred to as a super-Earth because outside of countless similar characteristics between Kepler-452b and planet Earth, Kepler-452b is much larger and much older. The planet’s diameter is 60 percent larger than Earth’s and it is 20 percent brighter. It is 6 billion years old, which is 1.5 billion years older than our planet. Based on past planetary research, Kepler-452b’s large size creates a greater likelihood of the planet being rocky, which is essential in order for life to arise (Austin, 2015). It orbits a sun-like star at a 5 percent greater distance than the Earth orbits the sun (Kepler and K2, 2015).

Kepler-452b was discovered in may of 2014 during a test run of the Kepler Science Operations Center when a performance assessment of the Center’s ability to inspect small, cool planets was being conducted. The very first transit signature of Kepler-452b featured four 10.5 hour long, deep transits spaced 385 days apart, a radius of 1.1 R, and an equilibrium temperature of 221 K. These characteristics supported the planetary nature of Kepler-452b even though the radius and equilibrium temperature were overstated in the first transit signature. Due to overly aggressive automatic consistency checks, this transit signature had not been identified in the Kepler data during the four years prior to its discovery (Discovery And Validation of Kepler-425b , 2015).

Kepler-452b is in the habitable zone (NASA, 2015). Being in the habitable zone means that the temperature is in the right zone (273K to 373K) where water can exist in its liquid form on the surface of the planet (The Habitable Zone , n.d.). Kepler-452b has been in the habitable zone of its star for 6 billion years. This provides tremendous opportunity for the start of life on this planet. Furthermore, the type of star that the Kepler-452b planet orbits is a G2 star which is a G class star. Only 3.5% of all stars are in the G class. Coincidentally, the sun is a G2 star, similar to the star of Kepler-452b. These stars have a surface temperature of 5,800K and a lifetime of 10,000 million years (The Classification of Stars, n.d.).

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