* Astronomy

Some solar flares may be caused by dark matter particles called axions spewing out from the centre of the Sun, new calculations suggest.
Solar flares are sudden changes in the Sun's brightness thought to be caused when twisted magnetic fields on the Sun snap and reconnect explosively.
But they could also be caused by dark matter, the mysterious entity that makes up most of the universe's mass if it is made up of theoretical particles called axions.

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Title: The photospheric solar oxygen project: I. Abundance analysis of atomic lines and influence of atmospheric models
Authors: Elisabetta Caffau (GEPI), Hans-G. Ludwig (GEPI, CIFIST), Matthias Steffen (AIP), Thomas R. Ayres (CASA), Piercarlo Bonifacio (GEPI, CIFIST, INAF-OAT), Roger Cayrel (GEPI), Bernd Freytag (CRAL), Bertrand Plez (GRAAL)

The solar oxygen abundance has undergone a major downward revision in the last decade, the most noticeable one being the update including 3D hydrodynamical simulations to model the solar photosphere. Up to now, such an analysis has been carried out only by one group using one radiation-hydrodynamics code. We investigate the photospheric oxygen abundance considering lines from atomic transitions. We also consider the relationship between the solar model used and the resulting solar oxygen abundance, to understand whether the downward abundance revision is specifically related to 3D hydrodynamical effects. We perform a new determination of the solar photospheric oxygen abundance by analysing different high-resolution high signal-to-noise ratio atlases of the solar flux and disc-centre intensity making use of the latest generation of CO5BOLD 3D solar model atmospheres. We find 8.73 < logNoxygen/Nhydrogen +12 < 8.79. The lower and upper value represent extreme assumptions on the role of collisional excitation and ionisation by neutral hydrogen for the NLTE level populations of neutral oxygen. The error of our analysis is ±0.04 ± 0.03 dex, the last being related to NLTE corrections, the first error to any other effect. 3D ``granulation effects'' do not play a decisive role in lowering the oxygen abundance. Our recommended value, considering our present ignorance of the role of collisions with hydrogen atoms on the NLTE level populations of oxygen, is log(Noxygen/Nhydrogen) = 8.76 ± 0.07. The reasons which have led to lower O abundances in the past are identified as (1) the lower equivalent widths adopted, and (2) the choice of neglecting collisions with hydrogen atoms in the statistical equilibrium calculations for oxygen.

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NASA's sun-focused Solar Terrestrial Relations Observatory, or STEREO, twin spacecraft unexpectedly detected particles from the edge of the solar system last year. This helped scientists map the energised particles where the hot solar wind slams into the cold interstellar medium.
The two STEREO spacecraft were launched in 2006 into Earth's orbit around the sun to obtain stereo pictures of the sun's surface and measure magnetic fields and ion fluxes associated with solar explosions. From June to October 2007, sensors aboard both STEREO spacecraft detected energetic neutral atoms originating from the same spot in the sky, where the sun plunges through the interstellar medium.

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Australian National University (ANU) astronomers have found there is nothing special about the Sun after conducting the most comprehensive comparison of it with other stars adding weight to the idea that life could be common in the universe.
Scientists have long argued about whether or not the Earth has some special characteristics that led to the evolution of life. PhD researcher Jose Robles and Dr Charley Lineweaver from the Planetary Science Institute at ANU contend that this is a difficult question to answer because we dont have information about other Earth-like planets.

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