Do planets form around lone stars, multiple stars, or both? Do we know this yet? Since about 1990 astronomers been able to detect planets around other stars, using a couple different techniques, which is amazing.

By this point, do we know whether planets form only around single systems, only around multiple systems, or both??

(Surprisingly you can't find this general issue explained in popular writing. I think it's "obvious background knowledge" to experts, hence just doesn't get outlined explicitly in popular writing.)

So, as of mid 2016:

(i) About how many exoplanets do we know of (say, with good certainty),

(ii) In fact, how many (if any) of these are around single-star systems?

(iii) How many (if any) are around multiple-star systems?

If indeed it is possible to have planets in multiple systems: is it just a planet going around one of the stars, or is "all the way around both" known?
There are currently 3424 planets identified (including those in the Solar System and unconfirmed exoplanets). Of these, 3310 are confirmed exoplanets.

Out of the 3424, 180 are in binary (or multiple) star systems. Of those, 28 are circumbinary. I am not certain if any circumternary planets have been identified, though I know some circumternary disks have.

It is more difficult to identify circum-n-ary planets than those that only revolve around one star, so these numbers might not precisely represent the actual proportions.

Source:


Open Exoplanet Catalogue