|Exoplanet Orbital period vs. age of host star|
However, what if not all the Hot Jupiters result from natural processes? After all, it didn't happen with any of the four gas giants in our solar system. They migrated over time, but nowhere near that far in. Once we have more statistics on exoplanets we should be able to see if older stars are acquiring hot Jupiters, which would be weird and raise questions, which is what we like here.
A Hot Jupiter's orbit has very low energy compared to the energy of a cool Jupiter. We are talking really massive amounts of energy. The amount of energy a planet in a circular orbit has in its orbit increases as its distance from it's star decreases, so you have to take energy out of the orbit to move it inward. That energy has to go somewhere.
If you took our own Jupiter (a middlin' mass as Hot Jupiters go), and sucked energy out of its orbit until it was one tenth as far from the sun as the Earth (that would be a rough time for the Earth on the way in, so let’s don’t), the amount of energy you would have to remove would be a bit more than 40 trillion trillion kiloWatt hours. If you took a million years to do it (say, until the next time the Cowboys win a Superbowl), this would be require a rate of energy loss a million times the power output of the Earth's electrical generating capacity (approximately 2 Terawatts at present). That is roughly 10 times all the solar energy falling on the Earth. Some of the hot Jupiters out there could have given up quite a bit more energy than that, depending on how far out from their star they began their orbit, their mass, and the mass of the star.
With that kind of local energy generation capacity, what could you do? My first thought: antimatter. Antimatter (say, positrons) is inefficient to make, but is a great way to store energy compactly for interstellar flight. Even more exotic things might be possible - small wormholes, or even warp drives. No doubt, it would be something I haven't thought of. Once again, the question is more interesting than answer.
Do I believe this has happened? No, but I don't know why it's impossible, and as we search for large scale evidence of advanced civilizations, Hot Jupiters are low hanging fruit. The test is to see if there are any older solar systems in the process of acquiring a Hot Jupiter - a big planet with an unexplainable decreasing trend in its orbital period. We probably haven't been observing these planets long enough to measure that, but I hope we'll have observations with smaller error bars over longer period of time before I am too old to appreciate it.
BTW, the exoplanet data is nicely curated over at http://exoplanet.eu/ . Go over and have a look.
The Dream of an Open Channel by Paul Carr is licensed under a Creative Commons Attribution- ShareAlike 3.0 Unported License.