12 May 2023
The GREGOR solar telescope just started its new observing season on Tenerife, using, among others, a modern imaging instrument recently developed by scientists from the Leibniz Institute for Astrophysics Potsdam (AIP). The presented image is a showcase for the high-resolution capabilities of the instrument, approaching the theoretical limit of the telescope.
The new improved instrument called HiFI+ is installed at the 1.5-metre GREGOR solar telescope at Observatorio del Teide on the island of Tenerife and began its observations in 2022. The collage shows a best-of collection of various scenes on the solar surface including pores, sunspots, and quiet-Sun regions. These were observed in an area of near-infrared light, which contains spectral absorption lines formed by the titanium oxide (TiO) molecule. Bright points in the images are indicative of small-scale magnetic fields. The scientists used image restoration methods to improve image quality so that the smallest visible features approach the theoretical resolution (diffraction-limit) of the GREGOR telescope, which is about 0.1 seconds of arc or 70 km on the solar surface. Time-series with one restored image every 6–12 seconds allow scientists to study the solar atmosphere at different heights. The high-resolution TiO images assembled in this collage offer a first glance at the performance of HiFI+ and provide an outlook of what is to come in the 2023 observing season. HiFI+ was developed by AIP’s Solar Physics Section. The team (Carsten Denker, Meetu Verma, Ioannis Kontogiannis, Alex Pietrow, Aneta Wisniewska, and Robert Kamlah) commissioned the instrument in 2022/23, developed the data processing pipeline, and created a common research environment, which makes science-ready data available to the GREGOR consortium, scientists from other institutes, and the public.
HiFI+ consists of three camera control computers with two synchronized cameras each, which record images at a rate of up to 100 frames per second. These high frame rates are needed for frame selection (“lucky imaging”) and image restoration. The instrument thus achieves near-diffraction-limited imaging in six spectral windows across a field-of-view of about 55,000 km × 44,000 km on the solar surface. One channel isolates the core of the hydrogen Hα line showing structures about 1500 km above the solar surface, one channel in the blue part of the spectrum is used to estimate the blackbody temperature of the Sun, and four channels observe spectral signatures of small-scale magnetic fields at different heights in the atmosphere.
The GREGOR solar telescope was built by a German consortium under the leadership of the Leibniz Institute for Solar Physics in Freiburg with the Leibniz Institute for Astrophysics Potsdam (AIP), the Institute for Astrophysics Göttingen, and the Max Planck Institute for Solar System Research in Göttingen as partners, and with contributions by the Instituto de Astrofísica de Canarias and the Astronomical Institute of the Czech Academy of Sciences.
[Image]
Collage with an overview of all solar features observed with HiFI+ during the 2022 observing season at the GREGOR solar telescope: pores, sunspots and the quiet Sun.