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Beyond Earthly Skies

Influence of Hot Jupiters on their Host Stars

8 Apr 2014, 22:00 UTC
Influence of Hot Jupiters on their Host Stars
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A star’s magnetic activity allows it to extend its influence far beyond its surface. The Sun’s magnetic field extends billions of kilometres into space, far beyond the orbit of Pluto. Phenomena such as stellar flares and coronal mass ejections are magnetically induced processes that can profoundly influence the atmospheres of close-in exoplanets. It is well established that the magnetic activity of a star depends on its rate of rotation. A star’s rotation gradually slows as angular momentum is carried away by the stellar wind. As a result, the magnetic activity of stars like the Sun decreases over billions of years.Nevertheless, stars hosting hot-Jupiters (i.e. massive planets in close-in orbits) can maintain fast rotation rates and hence high magnetic activity. In a study by K. Poppenhaeger and S.J. Wolk (2014), 5 binary star systems with widely-spaced stars (over 100 AU apart) were observed in X-rays. For each binary system, one star is known to host a close-in massive planet, while the other star does not have a detected planet and acts as a negative control. Using X-ray emission as an observational proxy for stellar magnetic activity, the stars in each binary system were observed with Chandra and XMM-Newton.The 5 binary star ...

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