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An international team of astronomers, including Dr Christian Thalmann of the University of Amsterdam, has discovered a ‘Super-Jupiter’ planet orbiting the subgiant star Kappa Andromeda. The discovery is important in helping to understand how planets are born.


The team have obtained images of the planet by detecting its heat radiation using the Subaru telescope on Hawaii. Kappa Andromeda is a subgiant star around 2.5 times the size of the sun, and is to date the largest star which has been found to have a planet in its orbit using this method. The team will publish its findings in the Astrophysical Journal Letters.



Planet formation around stars

Many astronomers have long thought that a planet system orbiting a large star such as Kappa Andromeda might be much like our own solar system, only bigger. But others predicted a maximum mass: if the parent star were too large, the intensity of the star's radiation would prevent the formation of planets. The discovery of this Super-Jupiter, or very light brown dwarf Kappa Andromeda b, shows that planets can form in the orbit of stars 2.5 times the size of our own sun. 


Discovery made using infrared imaging

The discovered Super-Jupiter is 12.8 times the size of Jupiter and the temperature on the surface is 1,430 Celsius. Kappa Andromeda is part of the young Columba constellation. As it is only 30 million years old, Kappa Andromeda b is still emitting heat from its formation and is easier to detect in the infrared spectrum.


Nevertheless, it is unusual for planets to be discovered using infrared imaging, especially where the distance between the planet and its parent star is comparable to just twice the distance between the sun and Neptune. Astronomers managed to filter out the light from the star by making a series of infrared images. By hiding the glare from the star in this way, the planet became visible.


For more information and photos, see the website of the Netherlands Research School for Astronomy.