Europe's largest Solar Telescope GREGOR unveils magnetic details of the
Sun

Date:
September 1, 2020
Source:
University of Freiburg
Summary:
GREGOR, the largest solar telescope in Europe, has obtained
unprecedented images of the fine-structure of the Sun. Following
a major redesign of GREGOR's optics the Sun can be observed at a
higher resolution than before from Europe.



FULL STORY ==========================================================================
The Sun is our star and has a profound influence on our planet,
life, and civilization. By studying the magnetism on the Sun, we can
understand its influence on Earth and minimize damage of satellites and technological infrastructure. The GREGOR telescope allows scientists to
resolve details as small as 50 km on the Sun, which is a tiny fraction
of the solar diameter of 1.4 million km. This is as if one saw a needle
on a soccer field perfectly sharp from a distance of one kilometer.


========================================================================== "This was a very exciting, but also extremely challenging project. In only
one year we completely redesigned the optics, mechanics, and electronics
to achieve the best possible image quality." said Dr. Lucia Kleint, who
led the project and the German solar telescopes on Tenerife. A major
technical breakthrough was achieved by the project team in March this
year, during the lockdown, when they were stranded at the observatory
and set up the optical laboratory from the ground up. Unfortunately,
snow storms prevented solar observations. When Spain reopened in July,
the team immediately flew back and obtained the highest resolution images
of the Sun ever taken by a European telescope.

Prof. Dr. Svetlana Berdyugina, professor at the Albert-Ludwig University
of Freiburg and Director of the Leibniz Institute for Solar Physics (KIS),
is very happy about the outstanding results: "The project was rather
risky because such telescope upgrades usually take years, but the great
team work and meticulous planning have led to this success. Now we have a powerful instrument to solve puzzles on the Sun." The new optics of the telescope will allow scientists to study magnetic fields, convection, turbulence, solar eruptions, and sunspots in great detail. First light
images obtained in July 2020 reveal astonishing details of sunspot
evolution and intricate structures in solar plasma.

Telescope optics are very complex systems of mirrors, lenses, glass
cubes, filters and further optical elements. If only one element is not perfect, for example due to fabrication issues, the performance of the
whole system suffers.

This is similar to wearing glasses with the wrong prescription, resulting
in a blurry vision. Unlike for glasses, it is however very challenging
to detect which elements in a telescope may be causing issues. The GREGOR
team found several of those issues and calculated optics models to solve
them. For example, astigmatism is one of such optical problems, which
affects 30-60% people's vision, but also complex telescopes. At GREGOR
this was corrected by replacing two elements with so-called off-axis
parabolic mirrors, which had to be polished to 6 nm precision, about
1/10000 of the diameter of a hair.

Combined with several further enhancements the redesign led to the sharp
vision of the telescope. A technical description of the redesign was
recently published by the Astronomy & Astrophysics journal in a recent
article led by Dr. L. Kleint.

European researchers have access to observations with the GREGOR
telescope through national programs and a program funded by the European commission. New scientific observations are starting in September 2020.


========================================================================== Story Source: Materials provided by University_of_Freiburg. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Lucia Kleint, Thomas Berkefeld, Miguel Esteves, Thomas Sonner,
Reiner
Volkmer, Karin Gerber, Felix Kra"mer, Olivier Grassin,
Svetlana Berdyugina. GREGOR: Optics redesign and updates
from 2018-2020. Astronomy & Astrophysics, 2020; 641: A27 DOI:
10.1051/0004-6361/202038208 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200901112205.htm

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