# Computing Jupiter's Thermal Time Scale!

1. Oct 24, 2012

### jkrivda

1. Jupiter radiates more energy than it receives from the Sun by 8.7x10-10L0. Jupiter's radius is 7.0x109cm and its mass is 1.9x1030g. Compute its thermal time scale. Could gravitational collapse power this luminosity for Jupiter's entire lifetime of 4.5 Gyr?

2. Kelvin-Helmholtz (aka thermal) timescale equation is given by: t=ΔEg/L . ΔEg=GM2/R ... so, t=GM2/RL

3. Not sure what to sub in for "L" in the timescale equation. I'm guessing I have to use the 8.7x10-10 to figure that out. Any tips in the right direction would be greatly appreciated!

2. Oct 24, 2012

### bossman27

L for the timescale equation is just the luminosity of Jupiter. 8.7x10-10Lo is referring to the intrinsic luminosity of jupiter as a fraction of the solar luminosity. Astronomical units that have that subscript that looks like a dot with a circle around it are solar units.

3. Oct 24, 2012

### jkrivda

so i just convert the solar luminosity fraction to erg/s and then plug and chug?