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.).
Extrasolar Planets Essay
Humans have longed to believe in extrasolar planets, as surely there have to be planets elsewhere in the universe. Claims of supposedly discovered extrasolar planets can be dated back to 1855 when Captain S. W. Jacobs from the Madras observatory, claimed that he had discovered a planet orbiting a binary system (Jacobs 1855), all the way up until 1991 when a team of astronomers announced then retracted the alleged discovery of an extrasolar planet around a pulsar star (Lyne and Bailes 1992). Planets are extremely hard to detect as they are a very faint light source and the light from its parent star is much brighter and essentially blocks out light from a planet (Winters 1996). It was not until 1992 when the first exoplanets were confirmed orbiting a pulsar star (Wolszczan and Frail 1992). Finally in 1995, the first exoplanet orbiting a main sequence star, a star like our sun, was discovered (Mayor and Queloz 1995).
The very first extrasolar planets were discovered to be two Earth-like planets orbiting a pulsar star (Wolszczan and Frail 1992). A pulsar star is a neutron star that is constantly emitting beams of radiation, these beams of radiation occur because of a misalignment of the neutron’s star’s rotation axis and its magnetic axis (Pulsars 2011). The misalignment coupled with a neutron stars intense magnetic field and rapid rotation cause it to create intense electric fields where electrons are accelerated to high velocities where they produce radiation in the form of light. Even though pulsar stars are always emitting radiation, they seem to pulsate in relation to far away observers because the rotation of the neutron star causes the radiation within its magnetic field to sweep in and out, “pulsate”, of an observer’s line of sight in a regular interval (Pulsars, 2011). These first extrasolar planets were discovered because of the effects they had on their stars pulsation. Planets have mass and therefore have an effect on their stars orbit causing it to wobble. The wobble in the case of a pulsar star is seen as the periodic delay in the arrival of the pulses from the pulsar star (Wolszczan 1994). Due to the nature of a Pulsar star we can detect perturbations in its orbit through its pulses but to detect perturbations in other stars orbits, astronomers use a stars radial velocity.
The radial velocity method was used to detect the first exoplanet, 51 Pegasi b (51 Peg b) around a main sequence star, 51 Pegasi (51 Peg). The radial velocity method uses the variations in velocity of a star due to the gravitational pull from an exoplanet (Lissauer 2002). Furthermore the velocity isn’t measured in terms of actual speed but in terms of light based on the Doppler effect. The Doppler effect occurs when a star moves. When it moves toward us, its wavelengths of light are shortened and when a star moves away from us, its wavelengths of light are lengthened. Through the continued observation of the Doppler effect on a stars spectrum of light, the...
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