Jan 12, 2011 06:59 GMT  ·  By
An artist's rendition showing how an exoplanet transfer angular momentum to its host star
   An artist's rendition showing how an exoplanet transfer angular momentum to its host star

At the 217th American Astronomy Society (AAS 2011) meeting in Seattle, a team of astronomers announce a discovery that could help experts explain how a certain class of solar systems appeared and developed. The exoplanet they analyzed in the research is a hot Jupiter-class gas giant.

Apparently, this space body is capable of feeding momentum into its host star, which basically means that it can make it rotate faster. The findings were presented by astronomer Edward Guinan, who is based at the Villanova University.

This discovery is very important because astronomers have thus far identified a very large number of star systems containing hot Jupiter planets. In fact, most of the 500+ exoplanets found to date are gas giants, Space reports.

It would appear that small rocky worlds, such as Earth, Mars and Venus, are the exception in our galaxy, rather than the norm. Only a handful of Earth-like planets has been discovered thus far.

During the study that led to these conclusions, astronomers looked at an exoplanet called HD 189733b, which can be found about 63 light-years away from Earth. It orbits a dwarf K type star in the constellation Vulpecula, which is about 80 percent the mass and diameter of the Sun.

However, the exoplanet orbits around its star at only 0.3 astronomical units (AU), the distance between Earth and our star. This means that a year at HD 189733b takes only about 2.2 days.

Such a close proximity most likely causes the entire system to be tidally locked. This means that the planet most likely always keeps the same face oriented towards the star, due to the gravitational tug the latter exerts. Our Moon is subjected to the same influences.

What sets this particular system apart from our own is the fact that the parent star appears to rotate twice as fast as the Sun does. Experts believe that the same magnetic and tidal interactions that keep the exoplanet locked are also causing the star to spin faster.

But there is a catch to this cosmic ballet, experts say. As the planet transfers its angular momentum to the star, it slowly grinds to a halt itself. This may explain why, in such systems, hot Jupiter planets orbit so close to their parent stars.

“One of the most amazing results of our team's research is that a planet-size body that is only 1/1000 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,” Guinan said.

“This study may help explain how and why hot Jupiters form and evolve. It may help explain this whole class of planets,” the expert concluded.