::Interactive Astronomy::

Oort Cloud

The Oort Cloud is a spherical area of influence over our Solar System. It seems to stretch to infinity, but scientists are extremely convinced that it exists around our Solar System. The density, mass, size of the Oort cloud has not been defined. Small objects, mainly comets make up the Oort cloud. They orbit the Sun in highly elliptical orbits within the Oort Cloud. Comet Hale-Bopp is an object in the Oort Cloud.

In 1950, Jan Oort derived the Oort Cloud’s existence. He had observed that many comets seemed to pass by Earth in a long fixed period pattern of several thousand or million years. He speculated that the comets might be in the orbit of something. Upon observation, new comets seemed to be visible through the telescope regularly each year. Oort thus believed that millions of them existed in orbit of other objects in the Solar System. As the comets pass by Earth in all varying directions, Oort concluded that the “Oort Cloud” as he had named, is a sphere.

By measuring the orbits of certain long trailing comets, scientists believe that the Oort Cloud is huge, between 5000 AU and 100,000AU.

Whether the comets would eventually be affected by some planet’s gravity and suffer a collision is unknown. Their fate is vague.

During the formation of our Solar System, space objects, which fail to form planets, start an initial orbit. They have two paths which will be decided which is which for each of them.

As the objects’ orbits are unstable, they either move and get deflected off a planet’s surface through collision, or have their orbits affected by Solar Radiation pressure (energy like light radiated from the sun which form a force) from the sun. They eventually escape into the Oort cloud. Nevertheless, due to the collisions, these objects low in mass and density in relation.

The rest are those rocky objects which are less dense and massive. They get fully eroded or destroyed by bumps with other objects like plantesimals, or through collisions with planets.

With these newly uncovered facts, the Oort cloud is less massive and dense as we all previously thought.

Besides its spherical shape, little is confirmed of its characteristics and composition.

Comets are balls of ice and dust. The difference between meteors and comets are that meteors occur in flashes while comets seem to move slowly across the sky. Comets are made up of main two parts, the head and the tail. The head is mainly the comet itself. The tail is formed when sunlight heats up the comet, causing the ice to vaporize and the gas as well as dust to escape from the area where the ice vaporized. These form a “mist” behind the moving comet which is known as the tail. A strange phenomenon is that the tail always points away from the direction of the sun. This is due to the Solar Wind which is blowing out from the sun and the debris of the comet in the opposite direction. A comet’s tail looks smooth and has a light yellowish colour as sunlight is reflected from it. The tail debris of a comet could also form a meteor shower when they pass through Earth’s atmosphere.

A more detailed classification of a comet:

Nucleus. A stable solid of ice, gas, dust and other substances.
Coma. A shrouding mist of water, carbon dioxide and other gases sublimed from the nucleus.
Hydrogen clouds. A great envelope of hydrogen gas surrounding the back of the drifting comet.
Dust tail. The most visible part of the comet to the naked eye. Also known as the “Tail”. It is made up of gases blown off the nucleus by the Solar Wind from the sun.
Ion tail. A trail of plasma mixed with rays and streamers behind the comet. It is formed from the chemical reactions between the comet’s chemical surface and the solar wind from the Sun.

The Kuiper Belt

The Kuiper belt is a flat elliptical plane of orbiting objects. It is a path identified by Gerald Kuiper in 1951. It consists of comets, asteroids and planetesimals. The path stretches slightly beyond the orbit of Neptune. The objects here orbit the sun. The bodies are classified into two distinct groups. Those orbiting Neptune in a 3 is to 2 synchronous resonance with a highly eccentric orbit, and the rest orbiting the sun independently in a less eccentric orbit. Pluto is the largest planet in the Kuiper Belt while Ceres is the most massive. These bodies are classified under one category called Transneptunian.

Another group of objects called the Centaur objects are those which are veteran objects in the Kuiper Belt. They orbit on the exterior of the Solar System. This is due to their orbit being gradually influenced by the larger outer planets e.g. Jupiter, over time.