The amount of the gravitational force doubles.
According to Newton's law of universal gravitation, the gravitational force \( F \) between two objects is given by the equation:
\[ F = G \frac{m_1 m_2}{r^2} \]
where \( G \) is the gravitational constant, \( m_1 \) and \( m_2 \) are the masses of the two objects, and \( r \) is the distance between their centers. If the mass of one object (let's say \( m_1 \)) doubles, while the other mass (\( m_2 \)) and the distance \( r \) remain the same, the gravitational force will also double because it is directly proportional to the masses involved.