If that is a TO220 package as I stated above you will have approx 14 watts across it without a heat sink you can only do approx 2 watts by the data sheet (65C/W). With a heat sink the TO220 package is 5C/W junction to case so 14 X 5 for 70C plus room temp of 25C – 30C for 100C for maybe 25C-50C left. So you need a heat sink that is 50C/14 watts for 3.6C/watt. You could add a series power resistor on the input side of the regulator to cut the power dissipated by the 7809
http://www.fairchildsemi.com/ds/KA%2FKA7809E.pdf