An artistic illustration of Dwarf Planet shows NASA's Dawn spacecraft arriving at the dwarf planet Ceres.
Image 1: An artistic illustration of Dwarf Planet shows NASA's Dawn spacecraft arriving at the dwarf planet Ceres. Ceres the most massive body in the asteroid belt and the Dawn spacecraft is the first mission to visit a dwarf planet. | Source: NASA/JPL-Caltech

What is a Dwarf Planet?

Dwarf Planet is a type of planet-mass object that is neither considered a complete planet nor a natural satellite, Dwarf Planet orbits a star directly. The gravity of the Dwarf Planet keeps it in a hydrostatically balanced shape.

Word “Dwarf Planet”

The term Dwarf Planet was adopted in 2006 after classifying the Sun’s orbiting bodies into three parts, which was brought about by an increase in searches for objects farther from the Sun than Neptune. These planets are similar in size to Pluto. The removal of dwarf planets from the planetary roster was both praised and criticized by the IAU i.e. International Astronomical Union.

IAU – International Astronomical Union

As of July 2008, the International Astronomical Union has identified five dwarf planets – Ceres in the asteroid belt, and Pluto, Haumea, Makemake, and Eris in the outer solar system. So far five dwarf planets have been discovered in our solar system, namely – Pluto, Ceres, Haumea, Makemake, and Eris.

Only two of these Ceres and Pluto are demonstrated in sufficient detail, that they actually fit the definition of the IAU. The IAU accepted Eris as a dwarf planet because it is more massive than Pluto. He later decided that unnamed trans-Neptunian objects with an absolute magnitude greater than +1 should be named under the assumption that they are dwarf planets. At the time (and still until 2019), the Haumea and Makemake met this secondary test. However, some scientists were still not completely convinced about Haumea.

History of Dwarf Planet

Astronomers discovered Ceres and other bodies between Mars and Jupiter in 1801, which had been considered planets for decades. Around 1851 and after, when the number of planets reached 23, astronomers began to use the term asteroid for small objects, thus naming them or ceasing to classify them as planets. gave.

In 1930, most astronomers reconsidered the planets of the Solar System after the discovery of Pluto, which included thousands of small asteroids and comets with nine planets. Pluto was considered larger than Mercury for nearly 50 years, but with the discovery of Pluto’s moon Charon in 1978, it became possible to accurately measure Pluto’s mass and determine that it was much smaller than earlier estimates Was. It was about one-twentieth of the mass of Mercury, making Pluto considered the smallest planet ever. However, it was still more than ten times the largest object in the asteroid belt. Ceres was also one-fifth of the mass of the Earth’s moon. In addition, some unusual features, such as large orbital eccentricity and a high orbital inclination, made it clear that it was a different object from any other planets.

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Astronomers began looking for objects in space in the 1990s in the same area as Pluto, now known as the Kuiper belt. Many of these shared the major orbital features of Pluto, and Pluto came to be seen as the largest member of a new class of objects, the Dwarf Planet. This led some astronomers to stop referring to Pluto as a planet. Thus many terms, including sub planets and planetoids, now began to be used for bodies known as dwarf planets.

As of 2005, the size of three trans-Neptunian objects was equal to the size of Pluto (Quaoar, Sedna, and Eris). It became clear that either they too would be classified as planets, or Pluto would be reclassified.

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The Eris was then known as the 2003 UB313, which was discovered in January 2005. It was thought to be slightly larger than Pluto, and some reports informally referred to it as the tenth planet. As a result, the issue became the subject of intense debate during the IAU General Assembly in August 2006. The IAU’s initial proposal included Charon, Eris, and Ceres in their list of planets. After several astronomers objected to this proposal, an alternative was drawn up by Uruguay astronomers Julio Fernandez and Gonzalo Tancredi. He proposed an intermediate class for round large objects. Pluto, Ceres, and Eris were also removed, thus removing Charon from the list.

The final resolution 5A of the IAU preserved this three-grade system for celestial bodies orbiting the Sun. –

The IAU… solves the planets and other bodies in our solar system, excluding satellites, which are defined in three different categories in the following ways:

  1. A planet is a celestial body that is (a) orbiting the Sun, (b) has enough mass for its own-gravity to overcome rigid body forces so that it is considered a hydrostatic equilibrium (almost round) shape, and (c) It balances the area around its orbit.
  2. A “Dwarf Planet” is a celestial body that is (a) orbiting the Sun, (b) has enough mass for self-gravity to overcome rigid body forces so that it is considered to be a hydrostatic equilibrium (almost round). (c) has not balanced the region around its orbit, and (d) it is not a satellite.
  3. All other objects, orbiting the Sun, except the satellite, will be referred to as “small solar system objects”.

Although many things arose about the classification of those planets (which revolve around other stars) but no conclusions were drawn, instead it was proposed to decide when such objects would be seen.

Exploration and discovery

On March 6, 2015, the Dawn spacecraft began orbiting Ceres, becoming the first spacecraft to orbit a dwarf planet. On 14 July 2015, the New Horizons spacecraft flew near Pluto and its five moons. Dawn spacecraft has also unearthed the former dwarf planet, Vesta. Saturn’s irregular satellite Phoebe has been discovered by Cassini spacecraft and Voyager 2, which also detected Neptune’s moon Triton. All three are considered to be dwarf planets, and hence their exploration helps in the development of dwarf planets.

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This Article was Published On: 7 August, 2019 And Last Modified On: 17 November, 2020

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