VTF achieves first light with support from IRSOL

A telescope alone is not enough. Even if it has a 4-metre primary mirror - indeed especially if it has such a mirror! - a telescope cannot operate unless it is equipped with state-of-the-art instruments. Such as the Daniel K. Inouye Solar Telescope (DKIST), which the US National Science Foundation installed in 2022 on the Hawaiian volcano Haleakala and which in recent days, after 15 years of project development, saw the activation of the Visible Tunable Filtergraph (VTF), the world's largest and most precise spectropolarimeter. A success to which IRSOL in Locarno also contributed.

It is what astrophysicists call "first light": the first image obtained from a new astronomical instrument. In the case of the VTF and DKIST, it is a 25,000-kilometre region of the Sun at a sunspot, taken at a wavelength of 588.9 nanometres. Each pixel corresponds to only 10 kilometres: a resolution never achieved before.

Sunspots are cooler regions of the photosphere, the region of the Sun from which the light we see comes. They form because intense magnetic fields prevent the 6,000-degree plasma from rising from the depths of the Sun. It is precisely the magnetic fields that can trigger the violent geomagnetic storms that sometimes strike the Earth, in the best case producing beautiful polar auroras, in the worst case causing even severe damage to the human technological infrastructure on which essential services depend. This is why the study of the Sun's active regions is one of the frontiers of astrophysics, not only for the knowledge it produces but also because of the need to perfect the predictive capabilities of space weather and protect sophisticated but fragile human civilisation.

With its high spatial, temporal and spectral resolution, the VTF will offer solar physicists new possibilities for understanding phenomena on the photosphere and in the layer above it, the chromosphere. It will be able to determine the temperature, pressure and velocity of the plasma and the intensity of the magnetic field at different altitudes.

Such an ambitious project is always the product of an international collaboration. In the case of the Visible Tunable Filtergraph participated,  in addition to the Institute of Solar Physics (KIS) in Freiburg and the Max Planck Institute for Solar System Research (MPS) in Göttingen, also the Aldo and Cele Daccò Solar Research Institute (IRSOL) in Locarno, affiliated to the University of Lugano in Switzerland. Indeed, IRSOL is home of the ZIMPOL, a high-precision spectropolarimeter. The knowledge and experience of IRSOL researchers proved indispensable in adding a new tool for mankind to protect itself.