public enum Planet {
	MERCURY(3.303e+23, 2.4397e6), VENUS(4.869e+24, 6.0518e6), EARTH(5.976e+24, 6.37814e6), MARS(6.421e+23, 3.3972e6), JUPITER(
			1.9e+27, 7.1492e7), SATURN(5.688e+26, 6.0268e7), URANUS(8.686e+25, 2.5559e7), NEPTUNE(1.024e+26, 2.4746e7), PLUTO(
			1.27e+22, 1.137e6);

	private final double mass; // in kilograms
	private final double radius; // in meters

	Planet(double mass, double radius) {
		this.mass = mass;
		this.radius = radius;
	}

	public double mass() {
		return mass;
	}

	public double radius() {
		return radius;
	}

	// universal gravitational constant (m3 kg-1 s-2)
	public static final double G = 6.67300E-11;

	public double surfaceGravity() {
		return G * mass / (radius * radius);
	}

	public double surfaceWeight(double otherMass) {
		return otherMass * surfaceGravity();
	}
}