Hot Jupiters have mis-aligned orbits ?

[Widdekind]

Employing the online exoplanets.org plotter, i played around, looking for parameters that distinguish Hot Jupiters (HJ) from "normal" planets. HJs hug their central stars; they have small orbital radii, and short orbital periods. So, i used "orbital period" on the X-axis of the plotter. Then i tried various other parameters, for the Y-axis. Inexpertly, one parameter does distinguish HJs from conventional worlds. That parameter is "spin-orbit misalignment" (SOMA). Unlike "normal" worlds, which tend to orbit in the equatorial plane of their host stars, the SOMA of HJs spans the range, from [math]-180^{\circ} < \lambda < +180^{\circ}[/math]. Inexpertly, HJs, and only HJs, tend to orbit spin-tilted stars, often tilted over entirely, like the planet Uranus in our solar system. Is this correct; is my understanding of "SOMA" accurate? If so, why might mis-aligned star spins & world orbits promote planetary migration, until the HJs spiral in, onto star-grazing orbits ?? For example, if the original proto-planetary disk did swirl around the central star's equator; then the HJ-to-be would have punched up through, and then back down through, said disk, every orbit. What might be the effects, of such "disk crossings" ?? Would some sort of "spiral density waves" tug the planet towards the star??

 

the angle between the stellar spin and the planetary orbit can be measured for transiting planets

 

 

 

http://www.exoclimes.com/topics/changing-views-on-spin-orbit-alignment/

http://exoplanets.org/plots

 

The following figure, from the following article, helpfully visualizes, and emphasizes, that HJs often orbit retrograde (which might make planet migration more likely). Inexpertly, b/c the SOMA of HJ are (apparently) random, roughly half of all HJs orbit (partially) retrograde; and, roughly half of all HJs show signs of "bloating" or "inflation", having planetary radii too "puffed up" for easy explanation. Could retrograde orbits somehow explain HJ inflation??

 

http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full_html/2011/03/aa16331-10/F3.html

http://www.aanda.org/articles/aa/full_html/2011/03/aa16331-10/aa16331-10-fig3.jpg

Edited October 1, 2012 by Widdekind