One of life’s early lessons is to not look directly at the Sun. Astronomers didn’t seem to get the memo, though, because they keep aiming equipment right at it. The latest images to come of our star are from GREGOR, Europe’s largest solar telescope, which just got a makeover.
What did you do during the COVID-19 lockdown?
Most of us might answer that question by talking about learning to bake, doing home projects, or getting really good at using TikTok. For the astronomers associated with GREGOR, located in the Canary Islands on Tenerife, Spain, their answer would involve rebuilding the third-largest solar telescope in the world (after Big Bear and McMath-Pierce in the US).
The telescope had been suffering from something akin to astigmatism, in which the curvature of the eye’s lens is distorted and causes blurry vision. To correct GREGOR’s astigmatism, the team had to replace two mirrors that were polished down to an accuracy of six nanometers, or about 1/10,000 the width of a human hair.
“The project was rather risky because such telescope upgrades usually take years, but the great teamwork and meticulous planning have led to this success,” said Dr. Svetlana Berdyugina, professor at the Albert-Ludwig University of Freiburg and Director of the Leibniz Institute for Solar Physics (KIS). Now we have a powerful instrument to solve puzzles on the Sun.”
Now that GREGOR’s vision is sharpened, it can capture images of the Sun as small as 50 km across. According to KIS, considering that the Sun measures 1.4 million km, this is the equivalent of seeing a needle on a soccer field 1 km away with perfect clarity.
The update has resulted in genuinely striking images of the Sun’s magnetic fields and sunspots (see below), representing the highest-resolution photos of our star ever taken by a telescope in Europe. The researchers say that the redesign will allow GREGOR (named because it is a Gregorian telescope) to enable the study of the Sun’s turbulence, convection currents, magnetic fields, solar eruptions, and more.
Details of the telescope’s reconstruction have been published in the journal, Astronomy & Astrophysics.