Upsilon Andromedae b appears to be responsible for increased chromospheric activity on its parent star . Observations suggest that it is a " hot spot " on the star around 169 ° away from the sub @-@ planetary point . This may be the result of interactions between the magnetic fields of the planet and the star . The mechanism may be similar to that responsible for the activity of RS Canum Venaticorum variable stars , or the interaction between Jupiter and its moon Io .