Knowing the level of a planet's magnetic field can be an important fact to know in the study of how they interact. But studying the fields of an exoplanet, outside of our solar system and orbiting a foreign star, can be a difficult task that researchers have not yet been able to achieve. Though in nearly two decades of looking past our solar system to investigate exoplanets, researchers have developed several methods to estimate magnetic fields at quite a distance.
And in a new study published this week in the journal Science, researchers from Lomonosov Moscow State University in Russia say that they have managed to estimate the magnetic moment of the planet HD 209458b, just outside of our solar system - an achievement that the team hopes will someday help us better estimate which exoplanets may inhabit life. By analyzing the magnetic moment and the shape of the planets' magnetosphere, in comparison to that of Earth, astronomers and computational physicists will better be able to assess not only the state of the planets' atmospheres, but also whether they are suitable to sustain life.
Known as "Osiris", Planet HD 209458b, is a hot Jupiter-like planet though only one-third the size and mass. It's a hot gaseous, giant planetthat is relatively well studied. In fact, it was the first planet where an outer atmosphere was detected, which made it a perfect model obsject for the scientists to develop their hypotheses about magnetic fields and the role they play in atmosphere maintenance.
"We modeled the formation of the cloud of hot hydrogen around the planet and showed that only one configuration, which corresponds to specific values of the magnetic moment and the parameter of the stellar wind, allowed us to reproduce the observations" co-author of the study Kristina Kislyakova says. And using this model, the researchers were able to pinpoint an exact value to match their observations.
That data utilized in the study was originally collected by the Hubble Space Telescope in the hydrogen Lyman-alpha line at the time of transit, when the planet crossed the stellar disc in between it and the Earth. After initially studying the absorption of the star radiation by the atmosphere of the planet, they were able to estimate the size and configuration of the gas cloud surrounding the hot Jupiter, as well as the magnetosphere.
To further add precision to their model, researchers considered multiple covariants that alter the interaction between the stellar wind and the atmosphere of the planet, including: ionization, gravitational effects, pressure, radiation, and spectral line broadening. And what the researchers found was that indirect observations of Osiris revealed an even smaller magnetosphere than what they expected before. And that their new methods, while not exact, were successful in given fairly accurate results for distant exoplanets.
"The planet's magnetosphere was relatively small being only 2.9 planetary radii corresponding to a magnetic moment of Jupiter" Kislyakova said. "This method can be used for every planet, including Earth-like planets, if there exist an extended high energetic hydrogen envelope around them."
