# Why don't we detect planets around OB stars and no terrestrial planets around A or early F stars?

Looking at an exoplanet database, I noticed that there are very few planets detected around main-sequence OBA stars, and most of them are gas giants/brown dwarfs. Why can't we detect low-mass planets around these stars?

• Did you just look at a table or a observation bias-corrected occurrence diagram? As it stands at the moment, e.g. in arxiv.org/abs/1902.04493 , OBA stars have significantly reduced giant planet occurrence rates compared to FGK, and the low-mass planets are missing probably due to detection biases (RV being much more difficult due to high stellar mass, and transits rely on large numbers which OBA's don't have). – AtmosphericPrisonEscape Mar 9 at 23:59

Radial velocities: OBA stars are 2-30 times the mass of the Sun. For a given planetary mass and orbital radius this decreases the radial velocity amplitude observed in the star as $$M_*^{-2/3}$$. However, given the precision of current spectrographs this would not prevent the detection of hot Jupiters/Neptune's, or even cool Jupiters. No, the big problem with hot stars is the lack of spectral lines and the broad width of these lines due to the intrinsic rapid rotation of these stars. This prevents achieving the precision necessary to detect exoplanets.