Comments on: Eris menggeser Pluto dalam ukuran dan massa http://langitselatan.com/2007/06/17/eris-menggeser-pluto-dalam-ukuran-dan-massa/ weblog astronomi indonesia Tue, 06 Jan 2009 09:58:16 +0000 http://wordpress.org/?v=2.7 hourly 1 By: astronomsableng http://langitselatan.com/2007/06/17/eris-menggeser-pluto-dalam-ukuran-dan-massa/comment-page-1/#comment-172 astronomsableng Sun, 17 Jun 2007 19:50:15 +0000 http://langitselatan.com/2007/06/17/eris-menggeser-pluto-dalam-ukuran-dan-massa/#comment-172 Definisi planet menurut IAU sebenarnya banyak dikritik oleh astronom-astronom lainnya. Ini salah satu kritik dari Scott Tremaine, pakar dinamika planet, misalnya (gue kopi langsung dari presentasi doski dia ya): <blockquote>Bad definition 4 (IAU): A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite. All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". Bad points: really complicated only works for the solar system hydrostatic bodies are not necessarily spherical (e.g., many asteroids)</blockquote> Yang paling penting, menurut Scott, adalah bahwa benda-benda yg setimbang secara hidrostatis tidak mesti berbentuk bola. Problemnya memang, menurut Scott, pengetahuan kita tentang proses pembentukan planet masih sangat minim. Definisi planet menurut IAU sebenarnya banyak dikritik oleh astronom-astronom lainnya. Ini salah satu kritik dari Scott Tremaine, pakar dinamika planet, misalnya (gue kopi langsung dari presentasi doski dia ya):

Bad definition 4 (IAU):
A “planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

A “dwarf planet” is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.

All other objects except satellites orbiting the Sun shall be referred to collectively as “Small Solar-System Bodies”.

Bad points:
really complicated
only works for the solar system
hydrostatic bodies are not necessarily spherical (e.g., many asteroids)

Yang paling penting, menurut Scott, adalah bahwa benda-benda yg setimbang secara hidrostatis tidak mesti berbentuk bola. Problemnya memang, menurut Scott, pengetahuan kita tentang proses pembentukan planet masih sangat minim.

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