Heena Chotani Hw2-1



Summary:

Planets are defined as celestial objects that’s true mass is ‘below the limiting mass for thermonuclear fusion of deuterium that orbits a star or stellar remnant.’This definition, however detailed, is not satisfactory to envelop the many complexities of space. The author argues an all-encompassing definition would be a formation based definition: planets are bodies formed through core accretion. To accomplish this, the author attempts to identify at what specific mass orbiting celestial objects no longer revolve around metal-rich solar-type dwarf stars. He theorizes that objects less than 10 times the mass of Jupiter formed through core accretion like giant planets, while object with mass greater than this amount through gravitational instability. 

The author used clustering algorithms with 146 systems cataloging the planets forming through core accretion and through gravitational instability. The mass that separates the two clusters is determined to be the maximum mass of celestial bodies that form through core accretion thus should be classified as planets. They then graphed the masses with the metallicity. They also graphed a moving median metallicity as a function of mass.

The results of the second graph with the first graph determined that low mass secondaries no longer only orbit solar dwarf stars when mass is greater than 10 times the mass of Jupiter. Thus it can be deduced  that celestial bodies with a mass greater than 10 times the mass of Jupiter do not form through core accretion. The maximum mass for objects formed by core accretion would be if the mass was greater than 10 times the mas of Jupiter. As a conclusion, the author proposes, due to the inefficiency of the current definition of planet and the outstanding data presented, the definition of planets be changed to his proposed definition and sub stellar objects above the threshold be defined as brown dwarfs.    

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