It's tricky to definitively say which solar system is the "second smallest" because we haven't discovered and characterized all the solar systems in the universe.

However, based on our current knowledge, the Kepler-37 system is a strong contender for being one of the smallest. It's home to Kepler-37b, which is smaller than Mercury and is the smallest confirmed exoplanet discovered so far.

Keep in mind that new discoveries are made all the time, and there might be even smaller solar systems out there waiting to be found!