Comets have been a source of much intrigue for man throughout the ages. From associations with divinity, literary metaphors and idioms to doomsday predictions through them by Hollywood (remember Deep Impact and Armageddon), yes they have acquired iconic status of lore. But from where do they exactly come from? This article will attempt to solve that mystery for you. But remember that as times change so does the theories of cosmologists.
They originate majorly from two areas of the solar system- the Oort cloud and the Kuiper belt. Each contains billions of these but such is the vastness of space in between them that each is separated from other by spaces as large the distance between the sun and earth.
The Kuiper Belt
Beginning just beyond Neptune’s orbit, it is about two billion miles or 3.2 billion km in width. It is separated from the sun by 4.8 billion km or 3 billion miles of space and extends to about 8 billion km or 5 billion miles. It seems to be flat disk comprised of icy debris. It lies in the ecliptic plane or the plane of the planet’s orbit. According to scientists their formation took place outside our solar system’s planetary part.
Apart from comets, the Kuiper Belt is home to much larger objects called KBOs or Kuiper Belt Objects in scientific nomenclature, some of which are large enough to be moons. Indeed some like Ceres, Pluto or Eris have indeed been conferred the status of “dwarf planets”.
The Oort Cloud
In contrast the second hub of comets way out at the extremities of the solar system a whopping 30 trillion km or 18 trillion miles from the sun, only 2 light years away from Proxima Centauri, the sun’s nearest peer. Unlike the Kuiper belt it is round in shape.
It just might so happen that such icy bodies are pulled of their orbits by a passing star and becomes a part of the solar system of that particular star and metamorphose as a comet. Such varieties are called long-period comets and have large orbits which are greater than 200 years.
Where Did that Particular Comet Originate From?
It is held that long-period comets or those travelling at angles to the eclipctic plane hail from Oort Cloud while the others originate from Kuiper Belt.
What About Jupiter?
Jupiter’s massive gravity is legendary in scientific circles and it sucks in comet like bodies from Oort Cloud or Kuiper belt into its own planetary family. They have solar orbits of 3-20 years.
How Were they Formed?
Some scientists hold that gravity assist of the big four Saturn, Jupiter, Neptune and Uranus helped these objects to be catapulted to the Oort Cloud. Some were thrown completely out of the solar system. And those who did not go the distance formed the Oort Cloud. Another theory as held by scientists is that comets owe their origin to dense molecular clouds to be found in interstellar space which was eventually caught by the Sun and thus the Oort Cloud was formed.