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Scientists have developed a new method of measuring the magnetic field of distant extrasolar planets, called exoplanets. Exoplanets are planets located outside our solar system that gravitate around a star. The researchers found the method by observing and measuring a specific exoplanet named HD 209458 b, situated 150 light-years from our solar system, in the constellation Pegasus.
HD 209458, also known as Osiris, is an exoplanet similar to Jupiter, only two times larger than Jupiter and 220 heavier than Earth. It orbits a star similar to our Sun in a very short period of time – a year on planet HD 209458 lasts just 3.5 Earth days. The planet is also very hot – about 1,800 °F temperature on its surface.
Understanding the magnetic field of such a planet is very important in understanding how it interacts with the spatial body orbiting near them. Planet Earth has also a magnetic field that protects humans and other living creatures from harmful cosmic radiation. The magnetic field also helps animals to migrate and find their way back home during their annual migrations. Thus by measuring the magnetic field of a distant planet, scientist might say if that planet can shelter life.
A group of Austrian scientists and a team of international physicists managed to estimate for the first time the value of HD 209458’s magnetic moment and its magnetosphere’s current shape. The researchers published their findings in the Science magazine. Maxim Khodachenko, Russian researcher working at a nuclear physics institute in Moscow, was also author of these findings.
HD 209458 was particularly used in the research because it is well studied by astronomers, since it is the first exoplanet whose atmosphere was detected. Astronomers usually use this planet as a model when studying other extrasolar planets.
In order to measure its magnetic field, scientists followed a set of steps. First, they observed the planet orbiting its star through the Hubble Space in the hydrogen Lyman-alpha line in the moment the exoplanet crossed its sun’s disc, as seen from Earth. Then they calculated the amount of star radiation HD 209458’s atmosphere absorbed. On theses facts, scientists estimated the volume and shape of the planet’s magnetosphere.
“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 parameters of the stellar wind, allowed us to reproduce the observations,”
Kristina Kislyakova, a Russian researcher in the project said. From now on, astronomers can estimate the size and shape of any exoplanet’s magnetosphere, including Earth-like planets, if they have a high energetic hydrogen cloud around them.