The Solar System is unlike any other: the "strangeness" we have attributed to distant exoplanets may be a matter of our own
The Solar System hosts, as far as we know today, eight planets: four small rocky planets, Mercury, Venus, Earth and Mars, and four huge gaseous planets, which answer to the names Jupiter, Saturn, Uranus and Neptune.
As for a possible Planet 9, the research is still open. But our Solar System is starting to look different from the others in an increasingly obvious way: with the analysis of more numerous solar systems, scientists seem to agree on one fact. Those exoplanets dubbed "cosmic oddities" are perhaps more standard than some of the planets orbiting the Sun.
How Solar Systems Form
We have yet to find a solar system that resembles our own. There are now plenty of solar systems found outside our galaxy, about 3600, but nothing like what happens around the Sun.
Gas giants have been found with orbits very close to their stars, rocky planets many times larger than Earth, and just about every other possible combination - except the one that forms our Solar System.
This has contributed to a peculiar question within the scientific community: what if the "cosmic strangeness" is not in the features encountered outside the galaxy, but is actually in our own system?
The first suspicions date back to the 1990s, with the discovery of the first exoplanets orbiting "normal" stars, called hot Jovian planets, orbiting their star so close that a year lasts just a few hours.
Accepting the ancient model that planets maintain nearly stable orbits from the point where they form, then the existence of gas giants close to their star would not make sense: the heat would vaporize everything, on this the scientific community has no doubt. The problem could be solved by adopting the so-called Nice model, formulated in 2005: the gas giants could migrate to the outermost orbits starting from positions very close to their star.
The theory of migration of planets would explain their position and also the formation of celestial groups such as Trojans orbiting Jupiter and the Kuiper belt, as well as give reason for the size of Uranus and Neptune - always considered too large to occupy orbits so far from the Sun. They may have gotten there.
The Great Turning Hypothesis holds that after its formation, Jupiter would have migrated inward into the system, then reversed course and headed for outermost orbits after capturing Saturn in an orbital resonance. The migration of Jupiter and Saturn could explain the current "strange" conformation of the Solar System.
But not even the model of the great turn can dispel doubts about the origin and evolution of our Solar System. It does not justify for example the composition of the planets: according to Stephen Mojzsis of CRiO (Collaborative for Research in Origins), "if Jupiter has migrated inward, then everything must have mixed, instead the Earth and Mars have completely different chemical compositions."
Not to mention that the Solar System is the only one of all the known ones to have no half-measures: there are small rocky planets and gas giants, but not even a single medium-sized celestial body, if you don't consider the hypothetical Planet 9.
Considering that these "medium" planets alone make up more than half of all known planets, it is rather strange that there are none in the Sun star system. The absence could still be explained by the migration of Jupiter, which may have "disturbed" the formation of a super-Earth or other "medium" planets.
It would seem increasingly clear that the "strangeness" so far attributed to exotic exoplanets detected in the depths of space is instead to be attributed to our Solar System, a "space oddity" of which we can only look for traces in other solar systems.