Could the planets around HR 8799 be brown dwarfs?

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We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of 100 Myr, not with the 1 Gyr age proposed from astroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the astroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs.