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A Brief Introduction To The Solar System – Part II


In the previous post I described about the sun and the planets in the solar system. But our solar system is not only the sun and the planets. It has many more other objects. In this post I will describe about them briefly.

Our solar system formed 4.5 billion years ago due to a gravitational collapse within a molecular cloud which formed our sun. The majority of the solar system consists of the interplanetary medium. The sun and the other planets resides in this medium. The interplanetary medium includes the interplanetary dust, cosmic rays and hot plasma from the solar wind.

Interplanetary Dust

The interplanetary dust consists of small particles which are important in scattering the sunlight and emitting thermal radiation. They are made during the collisions happened in the solar system. Cosmic rays are the high energy protons traveling through the solar system in the speed of light. They can be originated in the sun or outside of the solar system within our galaxy or nearby galaxies. Solar wind is a stream of charged particles released by the sun. The plasma in the interplanetary medium is made out of those particles. Due to the ejection of particles with the solar wind a geomagnetic storms are created.

Asteroids Belt

The planets in the solar system is divided into two groups. They are inner planets and outer planets. Between these inner planets and outer planets there is an asteroid belt. The asteroid belt consists of a large number of irregular shaped solid bodies. Many of them are smaller than planets. The total mass of the asteroid belt is about 2.39*1021 kg (about 4% that of the moon). They are called asteroids or minor planets. The half of total mass of the asteroid belt belongs to four main asteroids. They are Ceres, Vesta, Pallas, Hygiea. Only Ceres is large enough to consider as a dwarf planet and the other objects are not. The asteroids smaller than one meter are called meteoroids. Collisions between large asteroids occur but most of the asteroids are small and thinly distributed. Except for the main asteroids others are made out of a rocky formula or ice.

Centaurs

Minor planets or Centaur are a small solar system bodies that are located between Jupiter and Neptune. They usually cross one or more orbits in their journey around the sun. Because of these interactions the orbits of these centaurs become unstable and soon they can be ejected from the solar system.

Comets

According to NASA a comet is an frozen leftovers from the formation of the solar system. They are made out of frozen gasses, dust and rocks. Like all other objects the comets also keep orbiting the sun. When a comet get closer to the sun it is heated and releases the gasses. This process is called Outgassing. When frozen a comet has a size of a small town but when it is heated up it spread the gas into a round ball (coma) which is larger than a planet and a tail forms up to millions of miles. As of July 2019 6619 comets have been discovered. click to view comets visible in 2021

Trans Neptunian Objects

Trans Neptunian Objects or TNOs are any minor planet orbiting sun with a distance more than Neptune. Eris is known as the biggest TNO discovered until now. TNOs can vary in color. They are either grayish blue or red. As of 2020 there are 678 TNO that have been discovered.

Pluto

By NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker – http://pluto.jhuapl.edu/Galleries/Featured-Images/image.php?page=1&gallery_id=2&image_id=543, Public Domain, https://commons.wikimedia.org/w/index.php?curid=71082408

The most famous TNO is Pluto, discovered in 1930. Until recently Pluto was named as the 9th planet in the solar system. But since 1992 many objects with the same mass as Pluto were discovered within the region. In 2006 official definition was published to define the term planet and they are,

  1. the object must orbit around the sun
  2. The object must be massive enough to be rounded by its own gravity
  3. The object must have cleared the neighborhood around its orbit

By clearing the neighborhood means that an object is gravitationally dominant that there are no other objects other than its moons. Pluto failed to meet the 3rd condition as the mass of the Pluto was less than the other two objects in its orbit. Now Pluto is considered as a minor planet.

Fun Fact : In 2006 the word “Plutoed” was elected as the word of the year by the American Dialect Society. The word plutoed is referred to demote or devalue someone or something

Kuiper Belt

Kuiper belt is a donut shaped region located in the outer solar system. It is similar to Asteroid belt but larger in size. Many objects in the Kuiper belt are made out of frozen gasses such as methane, ammonia or water. It is home to dwarf planets such as Pluto and some of the planet’s moons such as Triton (Neptune) and Phoebe (Saturn) are suspected to be have originated in this region. Initially it was considered as the main repository for periodic comets.

Most of the solar system is still unknown. There are only theories have developed about the boarders of the solar system. Many space exploration projects were initiated to study about the solar system.

Fun Fact : The farthest known object of the solar system is a dwarf planet known as Farfarout which was first discovered in 2018

I have written about the sun and the planets in a previous post. You can read it here.

26 replies on “A Brief Introduction To The Solar System – Part II”

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