Detection methods for finding exoplanets are somewhat biased towards exoplanets in particular orbital alignments, or which are close to their host stars, or which are very massive. So, depending on what statistical and physical assumptions are made, there are numerous estimates of the average number of planets around each star in our Galaxy.
However, based on various studies, an average of between one and two exoplanets per star seems to be the most likely answer, giving as many as 400 billion planets in our Galaxy.
- Could two planets share the same orbit without colliding?
- Who really discovered the first exoplanet?
- How large does an object need to be for something to orbit it?
- What is the smallest known star in the Universe?