Astronomy

What is a Planet?

Introduction to the Planet

Planets are something every person has heard of, whether it’s a kid or adult. You might wonder what is a planet. It is known that Earth, Jupiter, and Mars are planets.

The Pluto and the Ceres were also planets earlier. However, a new discovery now triggers scientific debate about how to best describe them in a perfect and complete way.

what is a planet

Definition of Planet

A planet is an astronomical body. It orbits any star or any kind of stellar remnant.

Further, it is massive enough to be round through its own gravity, is not massive enough for causing the thermonuclear fusion. Moreover, it also clears of its neighbouring region of planetesimals.

The term planet is an ancient word. A naked can see five planets in the Solar System. As scientific knowledge became advance, the perception of humans changed.

In the year 2006, the International Astronomical Union i.e. IAU officially started a resolution defining planets in the solar system. This definition is controversial because it does not include many objects of the planetary mass that are based on where and what they orbit.

Although eight of the planetary bodies that are present since 1950 are planets under the current definition. Some celestial bodies are no longer visible as planets under the current definition of a planet. Thus, it is hard to tell what is a planet.

Planets are generally having two main types that are large low-density giant planets and the smaller rocky terrestrials. There is a total of 8 planets in the Solar System. In order of the increasing distance from the sun, they are 4 terrestrials, Mercury, Venus, the Earth, and Mars.

Also, the 4 giant planets are Jupiter, Saturn, Neptune, and Uranus. One or more than one natural satellite orbit six of the planets.

What is a Planet Made of?

We know, what is a planet but we are not sure how these planets are formed. The prevailing theory states that they are made during the collapse of a nebula into a thin disk of gas and the dust. A protostar forms at the core that is having the surroundings of the rotating protoplanetary disk.

Through the accretion, the dust particles in the disk accumulate steadily mass to form ever-larger bodies. Local concentrations of the mass we call planetesimals form, and these accelerate the process of accretion by drawing in additional material by their attraction by gravity.

These concentrations become denser ever until they collapse inward under the gravity for making protoplanets. After a planet reaches a mass that is nearly larger than the mass of Mars.

It begins to accumulate an atmosphere that is increasing. It greatly increases the capturing rate of the planetesimals by means of the atmospheric drag.

Depending on the accretion history of gas and solid. A giant planet, an ice giant, or a terrestrial planet might result.

The Planets in Order

There is a total of 8 planets in the solar system that are in increasing distance from
the Sun:

  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune

Furthermore, Jupiter is very large among all, whereas the mercury is the smallest. It is at 0.055 earth masses.

The planets in the solar system are divisible in categories that are based on their composition:

  • Terrestrials
  • Giant Planets
  • Gas Giants
  • Ice Giants

Attributes of Planet

Although every single planet is having unique physical characteristics. Furthermore, a number of broad commonalities are present between them.

Moreover, some of these characteristics like the rings or the natural satellites have only as to observable in planets in the solar system. Whereas others are also commonly observable in extrasolar planets.

Solved Question for You

Ques. The correct ascending order of distance of planets from the sun is:

(A). Mars, Earth, Jupiter, Saturn.
(B). Earth, Mars, Jupiter, Saturn.
(C). Earth, Mars, Saturn, Jupiter.
(D). Earth, Jupiter, Mars, Saturn.

Ans. (A). Mars, Earth, Jupiter, Saturn.

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