The exoplanet TrES-4 has been discovered in 2007. Its density is 0.24 gr/cm?? and its diameter is 1.7 times that of Jupiter. The orbital radius is 7.3.109 m and the orbital period is 3.5 days about a star which has a mass of 1.2 M??. It is not known why such low-density planets can exist. Low-density planets should quickly become more dense, due to gravitation.
Keywords: TrES-4, exoplanet, gravitation, gravitomagnetism, rotary star, gyrotation