Happy Valentine from our Sun

German-Norwegian team of scientists observes heart-shaped sunspot with GREGOR, the largest European solar telescope.

This heart-shaped sunspot was part of the active region 12338. It was recorded with GREGOR in the 'g-band' at 430 nm on May 7th 2015 close to the center of the solar disk.

Scientist-'selfie' inside the GREGOR telescope facing the 1.5m wide main mirror. From left to right: Morten Franz (KIS), Shahin Jafarzadeh (UiO) & Sven Wedemeyer (UiO)

The Kiepenheuer Institut für Sonnenphysik led the construction of the GREGOR telescope at the Observatorio del Teide on Tenerife. With a main mirror of 1.5 meter in diameter, it is one of the largest solar telescopes worldwide and allows scientist to study the physical processes on the Sun with unprecedented accuracy.

Sven Wedemeyer and Shahin Jafarzadeh from the University of Oslo and Morten Franz from the  Kiepenheuer Institut für Sonnenphysik in Freiburg were able to observe this heart-shaped sunspot with GREGOR on May 7th 2015. The picture was taken in the 'g-band' at 430 nm and shows a part of the active region 12338.

A sunspot develops in regions where a strong magnetic field disturbs the solar energy transport from the interior and radiative cooling decreases the solar surface temperatures of 6000 °C. In the center of the spot, you can see the dark, here heart-shaped, umbra, which is still about 4000 °C hot. In the umbra, the magnetic filed is oriented perpendicular to the surface. The umbra is surrounded by the brighter penumbra, which appears if the magnetic field bends and runs rather parallel to the solar surface. Then long and narrow strands develop, the so-called penumbral filaments. Since the magnetic field is weaker, more energy can reach the surface, and the penumbra is brighter. On the edge of the picture, you can see the structure of the undisturbed solar surface. The so-called granules are the visible top of Bénard cells, which develop due to the convective energy transport in the outer layers of the Sun.

Acknowledgements: "The 1.5-meter GREGOR solar telescope was built by a German consortium under the leadership of the Kiepenheuer-Institut für Sonnenphysik in Freiburg with the Leibniz-Institut für Astrophysik Potsdam, the Institut für Astrophysik Göttingen, and the Max-Planck-Institut für Sonnensystemforschung in Göttingen as partners, and with contributions by the Instituto de Astrofísica de Canarias and the Astronomical Institute of the Academy of Sciences of the Czech Republic. The observing campaign was supported by SOLARNET for the project "Vortex flows in the solar atmosphere". The SOLARNET Trans-national Access and Service Programme is supported by the European Commission (FP7, Grant Agreement 312495).“