This paper suggests that tidal evolution may destroy some Hot Jupiters. It points to the age of transiting planet stars as being younger.
Planetary Transits and Tidal Evolution
http://arxiv.org/abs/0809.1855 - Abstract wrote:
- Transiting planets are generally close enough to their host stars that tides may govern their orbital and thermal evolution of these planets. We present calculations of the tidal evolution of recently discovered transiting planets and discuss their implications. The tidal heating that accompanies this orbital evolution can be so great that it controls the planet's physical properties and may explain the large radii observed in several cases, including, for example, TrES-4. Also because a planet's transit probability depends on its orbit, it evolves due to tides. Current values depend sensitively on the physical properties of the star and planet, as well as on the system's age. As a result, tidal effects may introduce observational biases in transit surveys, which may already be evident in current observations. Transiting planets tend to be younger than non-transiting planets, an indication that tidal evolution may have destroyed many close-in planets. Also the distribution of the masses of transiting planets may constrain the orbital inclinations of non-transiting planets.
I would presume though that this might be extensible to any hot Jupiter system, not just transiting ones.
I did a tally of all the hot Jupiters from the Extrasolar Planets Encyclopedia whose ages were known (I excluded any hot Neptunes and hot SueprEarths). And found that with,
2 planets with periods less than two days. Average star age = 2.28 Gyr
11 planets with periods from 3 to 2 days. Average star age = 3.3483 Gyr
20 planets with periods from 4 to 3 days. Average star age = 3.9245 Gyr
8 planets with periods from 5 to 4 days. Average star age = 4.235 Gyr
6 planets with periods from 7 to 5 days. Average star age = 5.388 Gyr
7 planets with periods from 10 to 7 days. Average star age = 4.257143 Gyr
6 planets with periods from 20 to 10 days. Average star age = 3.765714 Gyr
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