Like a true king, the Sun will wear an exceptional “crown” to make the highly anticipated total eclipse unique which today, Monday 8 April, will be visible from North America: its outermost atmosphere, the solar corona, «may be 5-6 times larger than the diameter of the same star, due to the concomitance with the period of maximum solar activity”, as explained by Roberto Ragazzoni, professor of astrophysics at the University of Padua and new president of the National Institute of Astrophysics.
Observing the eclipse live or through the numerous live broadcasts available online will be an opportunity not to be missed, also because in Italy we will have to wait another three years to admire a similar show.
«The appointment is for August 2, 2027, when a total solar eclipse will be visible above Lampedusa», recalls Ragazzoni. The one on Monday 8 April could show us our star in a rather familiar guise.
According to Ryan French, a solar physicist at the National Solar Observatory in Boulder, Colorado, the filamentary protuberances of the corona will extend not only from the equatorial region, as in periods of minimum activity, but from the entire solar disk, branching out in every direction just as in the drawings some children. Predicting the shape of the solar corona is not just a pastime to while away the wait for the eclipse, but a real scientific research activity.
A team of NASA experts who deal with predictive science has in fact developed a computational model that produces updated forecasts in almost real time, thanks to data relating to the magnetic field of the solar surface (photosphere) collected by the Solar Dynamics Observatory space telescope. The model, developed by NASA's Pleiades supercomputer, will be compared with the images of the eclipse that will be taken on Monday to verify how much we really know about the dynamics that move the electrically charged gas (the so-called plasma) of the corona.
Knowing this part of the solar atmosphere is crucial, because it gives rise to wind and solar storms that can affect the Earth, causing spectacular phenomena such as the aurora borealis but also interference with the normal functioning of satellites, GPS, radio communications and electricity grids.
Monday's eclipse will be an important test for current theories, as has already happened for other eclipses in the past that have marked the history of science. One of the most memorable was that of May 29, 1919, which allowed the general theory of relativity developed by Albert Einstein only a few years earlier to be tested.
«By measuring the position of the stars around the lunar disk it was possible to demonstrate that the immense gravity of the Sun bends and distorts the light arriving from more distant stars as predicted by relativity», recalls Ragazzoni. «It was the true consecration of a theory that until then had remained confined to a narrow scientific field and which today is the basis of many everyday technologies such as GPS».