The Sun in X-rays. Past, STIX, Future

Tomasz Mrozek

Fifty-one years ago, on 28 November 1970, an instrument constructed in Wrocław took a solar X-ray image. It was a starting point for developing a solar X-ray group in Poland. At present, the group consists of scientists and engineers from the Solar Physics Division of Space Research Centre Polish Academy of Sciences (CBK PAN) and Astronomical Institute, University of Wrocław. Solar physicists from Astronomical Institute are mainly concentrated on data analysis and numerical modelling. CBK PAN team, apart from data analysis and numerical modelling, constructed instruments that flew outside the Earth’s atmosphere performing imaging and spectroscopy of solar flares in X-ray regime. The sum of experience gathered during all these years resulted in cooperation in the Spectrometer Telescope for Imaging X-rays (STIX) instrument mounted onboard the ESA interplanetary mission Solar Orbiter. STIX is the X-ray imaging spectrometer that is aimed to observe solar flares in the range of 4-150 keV. Its angular resolution is typical for coded aperture imagers, 7 arcsec, but it will approach the Sun as close as 0.3 au. Therefore, the spatial resolution will reach an unprecedented 1500 km. With the high energy resolution, of the order of 1 keV, we expect many exciting discoveries to be made with STIX in the near future. Since launch on 10 February 2020, STIX performs perfectly. Thus, by ESA decision, it is the only instrument onboard Solar Orbiter which is operated nonstop giving opportunity for uninterrupted registration of solar X-rays. More similar instruments are expected to be launched into geocentric and heliocentric orbits in the next few years. This will give an opportunity for stereoscopic hard X-rays (HXR) imaging opening up a completely new era of solar flares observations.

Proceedings of the Polish Astronomical Society, vol. 12, 129-137 (2022)

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