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Sandwiched planet formation may arise as the result of gas and dust being squeezed between large planets
Smaller planets might be born when gas and dust are squeezed between larger worlds, like the S filling in a cosmic sandwich. The newly suggested process, dubbed ‘sandwiched planet formation’, would occur in the massive discs of planet-birthing gas and dust that swirl around stars in their infancy. Around 4.5 billion years ago, the Solar System itself would have existed as one such disc around the infant Sun, from which the planets arose.
This new theory of planet birth was developed by researchers at the University of Warwick. According to sandwiched planet formation, two large planets already present in the protoplanetary disc would restrict the flow of dust inwards through the flattened cloud of gas and dust. This results in matter collecting between the planets, with dense patches of the protoplanetary disc collapsing to birth planets. This gathering of gas and dust between the original two large planets would then form a middle planet smaller than its two outer companions. The theory put forward by the team still needs to be confirmed, but if it is, it could explain how smaller planets like Mars are born.
It could even account for the creation of planets like Uranus, which themselves are quite large, but are still surrounded by even more massive worlds. “In the last decade, observations have revealed that rings and gaps exist in protoplanetary discs.
The gaps are where we expect planets to be, and we know from theory work that planets cause dust rings to form just exterior to them,” University of Warwick associate professor Farzana Meru said. “What exactly is happening in those rings poses an important question to astronomers around the world.”
Meru explained that sandwiched planet formation differs considerably from currently favoured models of planet formation that see planets form in sequence – starting at the inside of protoplanetary discs before moving to their outer regions – in addition to suggesting planets should get more massive further out in the disc. “What is also really interesting is that there are examples that we have found from exoplanet observations that actually show this sandwiched planet architecture – here the middle planet is less massive than its neighbours; it’s a reasonable proportion of the
