A gigantic exoplanet 63 light-years from Earth is doomed, slowly spiraling into its host star. But it's going out with a bang, funneling orbital enemy into its star and making it spin faster and faster, creative massive magnetic disturbances.


The planet in question has the snappy name of HD189733b, and it orbits the equally memorably named dwarf star HD189733A. The star is a small one, only about 80% the size of the Sun, while the exoplanet is slightly bigger than Jupiter. That said, the difference in sizes is enormous, as the star is roughly a thousand times larger than its planet. And yet the death throes of this planet are altering its parent star in a major way.

The planet is incredibly close to its star, only 3% the distance Earth is from the Sun, and it completes a rotation ever 2.2 days. Its star is sapping the planet of its orbital angular energy, which is causing the star to speed up its own rotation so that it's now spinning twice as fast as our Sun.


The faster the star spins, the greater its magnetic field, and the star and planet are forming an increasingly warped connection of magnetic and gravitational forces. Indeed, we know the planet is falling into its star and most likely doomed, but its possible these powerful forces could create a tidal-magnetic lock that stabilizes the planet's orbit and allows it to survive.

If we take this process back in time, we can start to see why a planet this big would get so close to its parent star in the first place. The planet has probably been stuck in a vicious circle for eons, as its star saps it of more and more orbital momentum the closer it gets, which causes the planet to fall still closer toward the star. The only question now that the planet has gotten so incredibly close to its star - it's at a distance less than ten times the star's own radius - is whether the magnetic and gravitational turmoil it's created will be enough to save it.

Chief researcher Dr. Edward Guinan explains that there are probably other planets out there that are having just as dramatic an effect on their parent stars, and indeed this finding could help explain the existence of all Hot Jupiters:

"Planetary systems like HD 189733 with short period, "hot-Jupiter" planets are very common – over a hundred have been discovered so far. HD 189733 and dozens of other planetary systems like it, many of which were recently discovered by NASA's Kepler mission, may also be undergoing the same process of strong magnetic interactions between their close-in large planets and their host stars. This study may help explain how and why hot Jupiters form and evolve. It may help explain this whole class of planets."


Although the planet is probably approaching its endgame, this is a story long in the making, as Villanova researchers estimate this star system has been around for over five billion years. The planet has had lots of time to earn its designation as a "Hot Jupiter", as other research has tabbed its average temperature at an incredible 1,500 degrees Fahrenheit.

Still, even if this phenomenon is common, as Dr. Guinan suspects, that doesn't make it any less extraordinary that a planet can affect a star so immensely bigger:

"One of the most amazing results of our team's research is that a planet-size body that is only 1/1000x times the mass of the host star can make such a large impact by magnetically interacting with its host star to the extent that it causes the star to spin up, activating a strong magnetic dynamo of the star that produces the observed strong X-ray coronal emissions, large starspots and other phenomena."


[217th AAS Meeting; artist's conception of planet's fate from presentation by Dr. Edward Guinan]