During your school days, you must have come across your science teachers talking about the Sun and its nine planets (which BTW are just eight now). Your teachers must have mentioned that the Sun, which is a giant star, is being orbited by planets, their moons, asteroids and comets. They must have told you that the Solar System, which is centred around the Sun, forms just a part of the Milky Way galaxy.
But have you ever wondered how big our Solar System actually is?
Before we begin explaining how gigantic the Solar System is, there are a few things that you should know beforehand. For starters, 1 Astronomical Unit (AU) is the distance between the Earth and the Sun, which is 149,597,870.700 kilometres.
1 AU (astronomical unit) = 149,597,870.700 kilometres or 149,597,870,700 meters.
Coming back to the Solar System, the distance up to 3.5 AU is called the Inner Solar System (consider it like some sort of secret society, only in this case it’s not a secret). This comprises of Mercury, Venus, Earth and Mars, which extend up to 1.5 AU. Beyond 1.5 AU lies the Asteroid Belt, which extends to 3.5 AU (523,592,547.45 kilometres) and contains the dwarf planet Ceres and proto-planet Vesta.
As we traverse further, we encounter the region that is called the Outer Solar System. This region is spread between 3.5 AU to 30 AU (4,487,936,121 kilometres) and contains the planets Jupiter, Saturn, Uranus and Neptune and Centaurs (which are the small bodies between Jupiter and Neptune).
Solar System at a glance (Photo: NASA)
Now comes the fun part. The region between 30 AU to 150 AU is the home to many mysteries and harbours the Kuiper Belt (the region beyond Neptune that consists of small bodies made of ice) from 30 to 50 AU. Between 40 to 150 AU (22,439,680,605 kilometres) lies the Scattered Disc region, which is the region of icy rocks where most comets originate from.
The region from 100 AU to 2,000 (299,195,741,400 kilometres) AU is like a mystery box. However, we did end up discovering a dwarf planet Sedna there. As we travel further, the region between 2,000 to 20,000 AU is the region of the Inner Oort Cloud, while the region between 20,000 to 100,000 AU is the region of the Outer Oort Cloud, which is where nearly all comets originate.
Heliosphere (Photo: NASA)
Our sun is like a giant ball of gases and it constantly emits charged particles into space. This is called the solar wind. It is so powerful that it can strip atmosphere off the planets and even produces stunning auroras on the Earth. The solar wind forms a bubble around the Solar System, which is called the Heliosphere. The region in the outer heliosphere where the solar winds become denser and hotter is called the Heliosheath and the boundary where the solar winds terminate is called the Heliopause.
Beyond this point, space is filled with the cosmic rays gases that mainly comprises of Hydrogen, Helium, Neon, Carbon and Oxygen in their ionic, molecular and atomic forms. As of now, NASA’s spacecraft are traversing in the Heliosheath region of the Solar System, which is the farthest region where mankind has ever reached.
