Astronomers classify planetary systems into four different categories based on the size and placement of the planets. After all, the structure of our own solar system is the most unusual.
Decades of telescopes dedicated to searching for worlds around stars other than our own Sun have so far yielded more than 5,300 exoplanets contained in 3,910 planetary systems. The abundance of data has allowed astronomers to classify these planets into different groups based on their characteristics. Rocky planets, gas giants, super-earths, mini-Neptune, water worlds, and more.
But can the planetary system itself be classified in a similar way? And if so, how does our own solar system stack up on a cosmic scale? was the goal of a new study by Swiss scientists who examined data from all 853 systems known to contain
From this analysis, the team settled on four major classes (similar, ordered, anti-ordered, and mixed) into which planetary systems are classified based on the size and placement of the planets. A similar system, the most common arrangement, is one in which the planets are all approximately the same size. For example, the TRAPPIST-1 system, which contains seven roughly Earth-sized rocky planets. An ordered star system is one where the inner planets are small and rocky, giving way to the gas and ice giants on the outskirts. Our own solar system falls into this group, and the team says it’s the rarest configuration.
Disordered systems are the opposite: the bigger the planet, the closer it is to the star, and the farther away, the smaller it is. And finally, there’s the mixed system, where there seems to be no rhyme or reason to the placement of the planets.
So how do planetary systems come to have these different configurations? Like many things, the team says it’s a mixture of “nature and nurture.” These include the mass of the planet-forming dust and gas disks and the heavy metals of the host star. It also partly depends on the planetary dynamics during the lifetime of the system.
“A ‘similar’ planetary system emerges from a fairly small, low-mass disk or star that contains very little heavy elements,” said lead author Lokesh Mishra. “Large, giant disks containing many heavy elements in stars give rise to more ordered and anti-ordered systems. The dynamic interaction of the will influence the final architecture.”
The more we learn about other planetary systems, the better we can understand our place in the universe.
The study was published in two studies in the journal Astronomy and Astrophysics.
Source: University of Bern
