Various astronomers have surmised that planetary pebbles were the original building units. That is for the heavenly bodies we see in the night sky.
How did such huge heavenly planets as Saturn and Jupiter form? Well, scientists have that one figured out now. They have found out that the largest planets were the first ones to get formed.
Both Jupiter and Saturn are composed of hydrogen and helium. They accumulated gas around a central core. The gas disks of planets usually last a million to 10 million years. That is the average life span of planetary disks.
The latest paper on the 'pebble-accretion' scenario, published in the 20 August issue of Nature.
“It really is a paradigm shift for how planets form,” says lead author Harold Levison, a planetary scientist at the Southwest Research Institute in Boulder, Colorado.
The earth took 30 million years in its formation. Others surmise that it may even have taken 100 million years to accumulate its layers. So the obvious question in everyone’s mind is how Jupiter and Saturn could have taken such a short time in their formation.
This is where the core accretion model comes in handy. Around a central core of ice and rock a mass of gas starts to accumulate. Yet this hypothetical postulate is full of holes. The first bone of contention is the original rock that the dust and gas formed layers around. How did such a large piece of core material come about in the first place.
It was thought that rocks merge with rocks. And mountains of material coalesced with other masses of stuff. However, this conjecture is shaky at best. The time span is too small for such large cores to form.
The duration dilemma has dogged the steps of researchers and experts right from the beginning. There seems to be no alternative to explain the time lag. The existence of Jupiter and Saturn thus remained a mystery.
But the new theories prove that the process was a little different than what it was hitherto thought to be. By a gradual and constant accumulation of small pebbles the solid cores got formed.
That is over a period of time that was roughly 10 million years. These planetary pebbles were objects that were frozen. As they gravitated towards the core they coalesced with the central portion.
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Over time the process became more efficient and so the largest planets of the solar system got formed. The action was a rare one. That is why there are only a few giant planets in the solar system. The rest of the planets are dwarves in comparison with Jupiter and Saturn.