Scientists suggest that the solar system's biggest planets, the colossal gas giants Jupiter and Saturn, have apparently began to form as tiny pebbles. In the astronomical sense, "pebbles" can also pertain to fractions of an inch to some few feet across, according to researchers from the Queen's University in Canada and the Southwest Research Institute in Texas.
More popular theories of how gas giants were formed include that their cores were formed during extreme cosmic collisions with other massive objects that are measured to be hundreds of kilometers in diameter.
However, this new study suggests that if these theories are correct, then the cores of the gas giants will not form rapidly enough to suck in and capture all the gases present in the solar system during that time which makes up most of their atmospheres today.
Prior studies already suggested that these gas disks on these planets will first form and last for about 1 to 10 million years where rocky planets such as Earth will take at least 30 million years and even 100 million years to form via a slow accretion process as larger material is bound to turn up later in the evolving solar system.
However, it is still an enigma to scientists how Jupiter and Saturn could amass so much material of this early solar system gas that can disappear faster than larger material. According to lead author of the study, Hal Levison from the Southwest Research Institute, this timescale of how gas giants and rocky planets were formed has been problematic for scientists, especially how Jupiter and Saturn could exist in the solar system.
Researchers now suggest in this new study that the accumulation of these cosmic "pebbles" have allowed their cores to build up faster, as opposed to the accretion theory of larger bodies.
Using computer simulation models, Saturn and Jupiter could have formed within the 10 million year timeline as they slowly accumulated a population of smaller planetary pebbles and even icy objects than average at a foot in diameter.
However, the team notes that this pebble accretion is not carried out in a rapid manner or else, the growing and evolving planets will not acquire enough gravitational forces to interact with each other. According to SRI scientist Katherine Kretke, if these pebbles form too fast, this pebble accretion will lead to the formation of hundreds of icy Earths. Their expanding cores then needed some time and space to compete with other pebbles where only two gas giants were formed in the end.
After gathering data from this new model, researchers have successfully predicted that this pebble formation process can also be observed in Neptune and Uranus and even the Kuiper Belt where millions of icy objects are floating that are solar system formation remnants.
This new study is published in the journal, Nature.