Exoplanets are a fascinating astronomy topic, especially the so-called \u201cHot Jupiters\u201d. They\u2019re overheated massive worlds often found orbiting very close to their stars\u2014hence the name. Extreme gravitational interactions can tug them right into their stars over millions of years. However, some hot Jupiters appear to be spiraling in faster than gravity can explain.<\/p>\n
<\/p>\n WASP-12b is a good example of one of these rapidly spiraling hot Jupiters. In about three million years, thanks to orbital decay, it will become one with its yellow dwarf host star. Both are part of a triple-star system containing two red dwarf stars. The hot Jupiter orbits the dwarf in just over one Earth day at a distance of about 3.5 million kilometers. That\u2019s well within the orbit of Mercury around the Sun. Thanks to that orbit and gravitational influence, one side of the planet always faces the star. That heats only one side and puts the surface temperature at about 2,200 C. Eventually heat flows to the opposite side, which stirs up strong winds in the upper atmosphere. The planet doesn\u2019t reflect much light, and astronomers have described it as a pitch-black world. <\/p>\n As if all that isn\u2019t odd enough, the gravitational pull of the nearby star distorts this hot Jupiter into an egglike shape. It\u2019s also stripping the planet\u2019s atmosphere away. So, it\u2019s no wonder astronomers described WASP-12b as a doomed planet.<\/p>\n According to conventional theory, a hot Jupiter planet like WASP-12b should create strong gravitational tidal waves between themselves and their parent stars. Those waves transfer energy, which tugs at the planet. That pulls the planet right into the star. Such a fiery death is definitely in WASP-12b\u2019s future. But, there\u2019s just one problem: it\u2019s getting sucked in faster than gravitational tidal waves can explain. What\u2019s happening?<\/p>\n A team of scientists at Durham University in England studied WASP-12b and they\u2019ve come up with an interesting idea. What if this hot Jupiter\u2019s fate is determined by magnetic fields? That\u2019s what Durham\u2019s Craig Duguid proposed in a recently published paper. Duguid\u2019s team thinks the strong magnetic fields inside some stars can dissipate the tidal waves generated by orbiting hot Jupiters.<\/p>\n How this works isn\u2019t completely confirmed yet, but here\u2019s the basic idea. Inwardly propagating internal gravity waves (IGWs) (such as those from the nearby hot Jupiter) move through a star. They eventually run into the star\u2019s magnetic interior. If that magnetic field is strong enough, it transforms them into magnetic waves. They move back outward and eventually dissipate. In the process, however, that dissipation causes a huge energy drain. The result is still the same as with gravitational tidal waves: the hot Jupiter loses energy and plows into its parent star. And, it could explain why some hot Jupiters spiral into their stars more quickly than expected.<\/p>\n In the paper, Duguid and his team used models of stars with convective cores\u2014such as F-type stars with masses between 1.2 to 1.6 solar masses. Astronomers suspect these experience weak tidal dissipation. The team used the known properties of these stars\u2019 interiors, along with estimates of their magnetic fields. For these stars, a convective core is the dynamo that generates the magnetic field. Although it\u2019s classified as a type-G star, WASP-12 fits into the study, thanks to its near-solar mass and radius.<\/p>\n So, is it just gravitational tidal waves pulling the planet in, or could the proposed magnetic field action be at work? Duguid and colleagues concluded that the magnetic field idea is very possible. They write, \u201cOur main result is that this previously unexplored source of efficient tidal dissipation can operate in stars within this mass range for significant fractions of their lifetimes. This tidal dissipation mechanism appears to be consistent with the observed inspiral of WASP-12b and more generally could play an important role in the orbital evolution of hot Jupiters\u2014and to lower-mass ultra-short-period planets\u2014orbiting F-type stars.\u201d<\/p>\n It\u2019s an interesting result. There are a great many hot Jupiters in the exoplanet archives, simply because they are the easiest exoplanets to observe. Some of them are spiraling in faster than expected. This leads the authors to suggest that additional studies of similar-type stars and their hot Jupiters could confirm the magnetic mechanism. In addition, future observations could help astronomers also understand the tidal wave theory and help place some constraints on the types of stars where it would operate.<\/p>\n Scientists Explain Why Some Exoplanets are Spiraling Towards Their StarsWhat\u2019s Tugging on Hot Jupiters?<\/h3>\n
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Exploring the Magnetic Mechanism Idea<\/h3>\n
Need More Data about Hot Jupiters<\/h3>\n
For More Information<\/h3>\n
An Efficient Tidal Dissipation Mechanism via Stellar Magnetic Fields<\/p>\nLike this:<\/h3>\n