Other star systems are ordered, with planets that seem like peas in a pod. However, our solar system seems to be special in more ways than one.
Why is our solar system a little messy?
The other known star systems in the galaxy are varied and diverse, and of course, quite different from ours. Their host stars differ from ours, their planet numbers and sizes differ from ours, so many other qualities differ from ours. Among all these glaring and interesting differences is the fact that the planets in other systems are usually close in size, with regular orbits around their stars. Perhaps this is something that we haven’t given much thought to because of the other compelling ways in which other systems are different, but it’s something that does bear exploring.
Explore that difference is exactly what a team of researchers set out to do, thereby discovering that our solar system isn’t as ordered as we may think it is.
The TRAPPIST-1 planets fit neatly together.
If you take a look at illustrations or diagrams of the solar system, you’d see that there isn’t much uniformity to be had among our planets. Our planets vary wildly in size, and the spacing of their orbits vary as well. Mercury’s radius, for example, is about 2,414 kilometers. Jupiter’s, meanwhile, is over 64,374 kilometers.
For a time, scientists thought that the way our solar system was ordered was the norm. However, a new study has found that numerous other systems have similarly sized planets running on evenly spaced orbits, much unlike ours. Since learning more about exoplanets, our view of our home system has changed.
Researchers reviewed the data on several exoplanets discovered by the Kepler observatory and obtained the high-resolution spectral data of 1,305 stars with 2,025 planets orbiting them. The data allowed the researchers to measure the size of the planets during their transit across their host stars. When the planets pass before their stars, the starlight dims.
The researchers were able to measure the size of the planets using the information on the dimming. The study included 909 planets from 355 multi-planet systems, all of which were located 1,000 to 4,000 light years away from Earth.
An illustration of a protoplanetary disk [Image by ESO/L. Calçada]
According to the findings, the size and orbital distances of planets in a system can be predictable if you know the size of just one of the planets or just one orbital distance. There was also apparently a weak correlation between the mass of the host star and the size of the planet, meaning that the size of the host star doesn’t influence the size of the planets. If there is some size variation among the planet, it’s because the planet closest to the sun is usually smaller.
Planets are formed from a disc of dust and gas surrounding a young star. It stands to reason, the researchers say, that if the disc is largely even, it would result in planets that are close together in size and have regularly spaced orbits. However, the researchers think that in the case of our solar system, gas giants Jupiter and Saturn may be to blame for the lack of uniformity. The two giants may have formed early on and disrupted the solar system. The next step would be to look for Jupiter-like exoplanets in multi-planet systems to see if there’s any weight in this theory.
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