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Tuesday, February 26, 2013

The Story of Ceres Becoming a Dwarf Planet

Ceres image taken from the Hubble  
Space Telescope in 2004. (Picture from:  
http://burritojustice.com/)
Currently Ceres, the largest object space located in the asteroid belt and has a length of about 950 kilometers, which has been included in the group of dwarf planets even though there are some large asteroids (Vesta, Pallas, and Hygiea) can be classified as a dwarf planet by considering size. Five dwarf planets (not asteroids) which was first introduced is Ceres, Pluto, Eris, Makemake and Haumea. Revision Ceres with native status as an asteroid later in the class of dwarf planets took place in 2006, along with the revision of Pluto with original status as a planet.

Families of the solar system is now divided into three, the planet (consists of 8 planets), dwarf planets, and Small Solar System bodies. The term minor planet to asteroid was abolished. Asteroids are space objects orbiting the sun and evenly distributed among the orbits of Mars and Jupiter. Ceres is one of the space objects ever of its status as the largest asteroid.

Ceres cutaway(Picture from:  
http://commons.wikimedia.org/)
Ceres is the largest object that inhabit the asteroid belt between the orbits of Mars and Jupiter. Based on the analysis in 2008, Ceres mass of about 9.4 x 1,020 kilograms. With the size of mass, comparable to one-third the mass of Ceres all that inhabit the asteroid belt asteroid, or about 4 percent of the mass of the Moon. The mass of Ceres enough to produce a nearly spherical shape due to its hydrostatic equilibrium. Ceres shape is very different from other large asteroids, such as Pallas, Juno and Hygiea, which have irregular shape. Ceres is included in the C-type asteroid, the asteroid that most elements of its content in the form of carbon.

Giuseppe Piazzi. (Picture from:  
http://www.daviddarling.info/)
Ceres was first discovered by an Italian astronomer Giuseppe Piazzi (1746-1826), on January 1, 1801. And then Piazzi named his discovery object as Ceres Ferdinandea. Ceres name taken from the name of the Roman goddess of agriculture, while Ferdinandea taken from the name of the king of Naples from Sicily, the King Ferdinand IV, as Piazzi tribute to the his king's. Furthermore, the object is more commonly known by the name of Ceres.

Before Ceres found, Johann Bode, a leader of Berlin observatory, through law known as Bode's law has predicted the existence of a planet between the orbits of Mars and Jupiter. Once Ceres discovered, then astronomers believe that Ceres (as stated Bode law) is "missing planet" is located between the orbits of Mars and Jupiter. Karl Friedrich Gauss, German mathematician, utilize Piazzi research results. Then Gauss calculating Ceres orbital period is 4.6 years or 4 years and 220 days.

When found in 1801, Ceres status as a planet. But then considered not a planet. The story of Ceres strikes as a planet after seven-year write-off, is similar to the story of Pluto strikes as a planet after 76 years (jump to related article). Once Ceres considered "missing planet", according to Bode law cause its orbits located between Mars and Jupiter. But then the question because Ceres was not large planet. Coupled after the discovery of many other similar objects that came to be known as the asteroid. Therefore Ceres categorized as an asteroid, not a planet.

For over a hundred years only known two groups of celestial objects, the planet as objects that are large and minor planets as small objects, including asteroids. The boundary between planets and minor planets during which there is no clarity. Limitation of size or large to distinguish between planets and asteroids were not based on physical considerations, but based on practical considerations to keep the asteroid Ceres and Pluto as a planet.

Then in 2006, the IAU (International Astronomical Union) create a new definition of planet. Broadly stated that the planet is a celestial with the characteristics as follows:
  1. Orbiting the sun,
  2. Has sufficient mass so that the force of gravity to overcome other external force, and with its hydrostatic balance has a nearly round shape,
  3. Had to get rid of other objects around its orbit.
The statement can be summarized that the planet is a celestial bodies around the sun, has a spherical shape, and is the sole dominant object in its orbit.

As for the dwarf planet even contain the word "planet" but it's really not a planet. Dwarf planet is defined as celestial bodies are characterized by:
  1. Orbiting the sun,
  2. Has sufficient mass so that the force of gravity to overcome other external force, and with its hydrostatic balance has a nearly round shape,
  3. Not to get rid of the other objects around its orbit,
  4. Not a natural satellite (moon).
With reference to the above definition, then Ceres, Pluto and Xena catagorized as dwarf planets. Other objects in the Solar System outside planets and dwarf planets are classefied as Small Solar System bodies. *** [EKA | FROM VARIOUS SOURCES | DEDE NURROSYID | PIKIRAN RAKYAT 14022013]
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