Observations of binary systems have confirmed ideas about the 'rejuvenating' effect of hot jupiters on their parent stars. The presence of a close and massive planet causes them to rotate faster and exhibit the high activity that is characteristic of young luminaries.
Hot Jupiters are exoplanets with a mass comparable to that of Jupiter but which are much closer to their stars than Mercury is to the Sun. This makes them extremely red-hot: even iron evaporates on such planets. However, the presence of hot Jupiter can have a 'rejuvenating' effect on stars. Such conclusions were reached by scientists from the Potsdamer Institute for Astrophysics (AIP), whose paper was published in the journal MNRAS.
The young star can be identified by its high activity, which is accompanied by frequent outbursts of material and powerful flares, including those in the X-ray range. However, the presence of a nearby massive planet also results. The tidal forces cause the star to rotate faster than it 'should' and its activity increases. This may lead to incorrect estimates of the age of distant stars.
Nikoleta Ilic and her colleagues at AIP have studied this "rejuvenating" effect, using the Chandra and XMM-Newton space telescopes. They have observed binary systems in which one of the partners has a hot Jupiter. The stars in such pairs are of the same age, so by comparing them to each other, the effect that the presence of a massive and nearby planet has on one of them can be highlighted. And to rule out the influence of stars on each other, scientists have only considered systems where the distance between participants is large enough.
X-ray observations have made it possible to assess the behaviour of stars in almost 30 such pairs. And they confirmed that in the presence of a hot Jupiter, the star looks and behaves more actively than its partner of the same age. "Before, we only had some curious indications (of this effect. - Ed.)," says Marzieh Hosseini, one of the authors of the paper. - Now we have statistical evidence that some planets can actually affect their stars and keep them young.
