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That star is a high-energy, small Sun will surprise scientists
A SMALL STAR with a mass approximately equal to the eight percent that of our Sun, was observed to emit a flare very intense (or flare) of x-rays. The star, known with the acronym J0331-27, belongs to the category of dwarf brown-class L. its mass is just enough to trigger the nuclear reactions that produce the energy emitted. The discovery, made by a team led by researchers at the national Institute of astrophysics, thanks to the observations of the space telescope Xmm-Newton from Esa, it is surprising the scientific community. Important also in this case, the contribution to research of Inaf Palermo. Up to now nobody had thought that eruptions of high-energy so powerful could be produced from a star of mass so small. The flare of X-rays produced by J0331-27 was observed on the 5th of July 2008 from the instrument Epic (European Photon Imaging Camera) on board of the observatory for X-ray Xmm-Newton.

In the space of a few minutes, the tiny star has released an amount of energy more than ten times greater than the most intense flares produced by the Sun. Current theories indicate that the flares are triggered by a sudden release of magnetic energy generated inside the star. This causes the charged particles to heat the plasma on the stellar surfaces, releasing this large quantity of radiation in the optical and in the ultraviolet and in the x-ray process allows you to release much of the stored energy in the star: it is precisely on this aspect that the new observations put the puzzle largest for scientists, as they had not expected the dwarf to brown class L could store enough energy in their magnetic fields give rise to explosions of this magnitude. This is because the energy can be placed in the magnetic field of a star only by charged particles, also known as the material ionized.

This material is created in high-temperature environments, but J0331-27, for the class to which it belongs has a very low temperature for a star, only 2100 kelvin (compared to the 6000 kelvin of the Sun). At these temperatures, it was thought it was not possible to generate charged particles-enough to feed so much energy in the magnetic field. "This is the scientifically most interesting discovery," says Beate Stelzer , of the Institute for astronomy and astrophysics of the university of Tübingen in Germany, and now in force at Inaf Palermo. The researcher is in the team which made the study, published in the journal Astronomy & Astrophysics.

How is it possible, then, that a star so the cold is able to produce a flare like that? To this question there is still a certain answer. On J0331-27 was also recorded only one flare, in spite of the star has been Observed, on several occasions, for a total of 3.5 million seconds of Xmm Newton, which is almost a thousand hours. "This fact seems to imply that a brown dwarf of class L uses a time greater than a star bigger to accumulate energy, which is then released suddenly with a flare of great magnitude," adds Stelzer.

The super-flare was discovered by analyzing the vast catalog of about 400 thousand X-ray sources of the XMM-Newton in the framework of the project, Extras, funded by the European Union and coordinated by Andrea De Luca , Inaf, Milan. The team, in search of particular phenomena, he has found bread for his teeth" just with J0331-27. Some stars similar to it were observed to emit flare very powerful in the band of visible radiation, but this is the first detection of unequivocal of a super flare in x-rays The wavelength is significant because it indicates from which region of the star's atmosphere comes from the super flare. The light in the optical range come from the deeper layers of the atmosphere of the star, in the vicinity of its visible surface, while the X-rays are produced in a highest area of the atmosphere. Understand the similarities and differences between this new super flare and those previously observed is now a priority for the team. But to do so, the key is to find other similar events. "There is still much to discover in the archives," says De Luca, "In a certain sense, I believe that this is the tip of the iceberg".

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