Now, I think this is something that many of you might not know or even might not have heard about it! You might now think of it as an ordinary cloud that we just see in the sky. But wait, my friend more has to come.
The Oort Cloud is a theoretical spherical cloud of predominantly icy planetesimals believed to surround the sun at distances ranging from 2,000 to 200,000 AU. It is the most distant region of our solar system, found far beyond Pluto, in the most distant edges of the Kuiper Belt.
If those distances are difficult to visualize, try using time as your ruler. At its current speed of about a million miles a day, NASA’s Voyager 1 spacecraft won’t enter the Oort Cloud for about 300 years and it won’t exit the outer edge for maybe 30,000 years. Even if you could travel at the speed of light, a journey to the Oort Cloud would require that you pack for a lengthy expedition.
While the planets of our solar system orbit in a flat plane, the Oort Cloud is believed to be a giant spherical shell surrounding the Sun, planets, and Kuiper Belt Objects. The Oort Cloud was discovered in 1950, and named after its discoverer Jan Oort, who resurrected it independently and hypothesized its existence to explain the behavior of long-term comets.
Although it has not yet been proven through direct observation, the existence of the Oort Cloud is widely accepted in the space science community.
Formation
A simple idea about the formation of the Oort Cloud is that these icy objects were not always very far from the Sun. After the planets formed 4.6 billion years ago, the region in which they formed still contained lots of leftover chunks called planetesimals. Planetesimals formed from the same material as the planets did. The gravity of the planets (especially Jupiter) then scattered the planetesimals in every way. Some planetesimals were removed from the solar system entirely, while others were tossed into eccentric orbits where they were still held by the Sun’s gravity, but were quite far that the galactic influences also pulled on them. Unlike the Kuiper Belt, which is concentrated along the solar system’s plane, the Oort Cloud envelopes the Solar System.
Structure and Composition
The Oort Cloud is thought to extend from between 2,000 and 5,000 AU (0.03 and 0.08 ly) to as far as 50,000 AU (0.79 ly) from the sun, though some estimates recognize the outer edge to be as far as 100,000 and 200,000 AU (1.58 and 3.16 ly). The Cloud comprises two regions.
1. A spherical outer Oort Cloud of 20,000 – 50,000 AU (0.32 – 0.79 ly),
2. A disc-shaped inner Oort (or Hills) Cloud of 2,000 – 20,000 AU (0.03 – 0.32 ly).
The outer Oort cloud may possess trillions of objects larger than 1 km (0.62 mi), and billions that measure 20 kilometers (12 mi) in diameter! Its total mass is not known to date, but assuming that Halley’s Comet is a typical representation of outer Oort Cloud objects, it has a combined mass of roughly 3×1025 kilograms (6.6×1025 pounds) or five piles of the earth!
The Oort Cloud-Comet relation
The Oort Cloud is made up of icy pieces of space debris. Sometimes that debris is jolted out of the cloud and falls toward the Sun, becoming comets. It can take thousands of years for an Oort Cloud comet to revolve around the Sun. In layman’s terms, we can say that the Oort Cloud is the region from where all long-period comets originate.
At last, a question might pop up now, What are these long-period comets? Long-period Comets are the ones that take more than 200 years to complete an orbit around the sun.
Author – Rinaan Guleria
Ignition Science 
Never knew about a layering for Solar System.
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