Tidal destruction of hot Jupiters?

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Tidal destruction of hot Jupiters?

Post by Sirius_Alpha on 13th September 2008, 12:01 pm

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


Last edited by Sirius_Alpha on 14th September 2008, 12:44 am; edited 1 time in total (Reason for editing : Forgot to add the actual link [rolls eyes])

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Re: Tidal destruction of hot Jupiters?

Post by Sirius_Alpha on 14th January 2009, 9:05 pm

Another article concerning the subject. Looks like HAT-P-2 may be safe, other than that, they're all screwed.

Falling Transiting Extrasolar Giant Planets
http://arxiv.org/abs/0901.2048

Abstract wrote:We revisit the tidal stability of extrasolar systems harboring a transiting planet and demonstrate that, independently of any tidal model, none but one (HAT-P-2b) of these planets has a tidal equilibrium state, which implies ultimately a collision of these objects with their host star. Consequently, conventional circularization and synchronization timescales cannot be defined because the corresponding states do not represent the endpoint of the tidal evolution. Using numerical simulations of the coupled tidal equations for the spin and orbital parameters of each transiting planetary system, we confirm these predictions and show that the orbital eccentricity and the stellar obliquity do not follow the usually assumed exponential relaxation but instead decrease significantly, reaching eventually a zero value, only during the final runaway merging of the planet with the star. The only characteristic evolution timescale of {\it all} rotational and orbital parameters is the lifetime of the system, which crucially depends on the magnitude of tidal dissipation within the star. These results imply that the nearly circular orbits of transiting planets and the alignment between the stellar spin axis and the planetary orbit are unlikely to be due to tidal dissipation. Other dissipative mechanisms, for instance interactions with the protoplanetary disk, must be invoked to explain these properties.

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Re: Tidal destruction of hot Jupiters?

Post by Lazarus on 24th January 2009, 2:14 pm

The question is what happens when the planet actually hits the star.
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