Does NASA feature anything devoted to the various kinds of
exosolar systems themselves? I know
there's this, but it was last updated in late 2017 and doesn't seem to amount to much.
As of June 1, there's supposedly "
a total of 659 known multiplanetary systems, or stars with at least two confirmed planets, beyond the Solar System." (
List of multiplanetary systems)
There's much ado about how "
our solar system is an anomaly". (1) Others have hot gas giants very close to the sun. (2) Exosolar systems are often much smaller than ours with the orbits of planets packed together within a few million miles rather than distributed across billions of miles. (3) The planets of other exosolar systems frequently feature crazy, eccentric orbits. (4) Most other stars with planets have companion stars rather than being a loner like the Sun.
As
this article asserted 5 years ago via
Eric B. Ford, apparently space scientists still haven't made much headway into developing a significant taxonomy for exosolar systems. "
These days, the challenge for planetary astronomers is to make sense of all these findings. Needless to say, and as Ford told me, it's still premature to put a single figure on of the total number of solar system architectures. We're still trying to make sense of all the planetary systems were finding, so there's not a single number," he noted. "That said, we are already starting to recognize that some architectures are showing up many times in our planet searches." [...] That said, Ford says there are several planet-types and solar system architectures that appear to be fairly common throughout the galaxy."
What he goes to on to tentatively say after that, back then, still pretty much echoes what
Bill Retherford expressed in the Forbes article above 4 years later.
My guess is that the bias towards large exoplanets might be a result of their being easier to detect from Earth, with the methods currently available. I'd speculate that there are lots of smaller planets out there that we haven't detected yet. If we imagine undetected Earth-sized planets, smaller Pluto-like bodies and asteroids, I'd guess that the vast majority of things orbiting other stars is the littler things.
![[Image: FOY9cfPVEAE8uSz?format=jpg&name=large]](https://pbs.twimg.com/media/FOY9cfPVEAE8uSz?format=jpg&name=large)