The total solar eclipse of April 8 promises to delight the millions of curious people who will mass along the band of totality, from Mexico to the island of Newfoundland, and whose view will not be obstructed by the clouds. But the eclipse will also be an opportunity for researchers to advance our scientific knowledge on various subjects. Quick overview.
There was a time, from the invention of the telescope until the beginning of the 20the century, where total solar eclipses were the occasion for major scientific discoveries, whether the exploration of the solar corona or the confirmation of a key prediction of Einstein’s general relativity, namely the deviation of the trajectory of light rays passing close to large masses.
Today, the major discoveries come more from solar telescopes, observation satellites and space probes, but there are still areas of knowledge to explore by taking advantage of these brief encounters between the Moon and the Sun.
Solar crown
The solar corona constitutes, in a way, the atmosphere of the Sun. This region, which begins above the visible surface of the Sun and extends millions of kilometers into space, is normally invisible because of its low luminosity, compared to that of the solar disk. During an eclipse, it appears as a ghostly halo around the silhouette of the Moon.
A great mystery about the corona continues to challenge astronomers: the temperature of the corona increases as one moves away from the surface of the Sun, when it should rather be the opposite. Scientists will take advantage of the April 8 eclipse to examine the different layers of the corona in the hope of finding answers to their questions. This will be all the more interesting as the Sun is currently near maximum activity and its corona is therefore likely to be more extensive and more dynamic than usual.
To carry out these observations, NASA plans to fly a stratospheric plane packed with scientific instruments in the direction of the movement of the Moon’s shadow, in order to take advantage of an eclipse lasting more than six minutes. Since this plane will fly much higher than commercial planes, it will be above the clouds and most of the Earth’s atmosphere, allowing cameras to take sharper images of the corona and capture lengths waves that do not reach the ground, such as infrared.
Ionosphere
The ionosphere is a layer of the Earth’s atmosphere that extends from approximately 100 km to 1000 km altitude. It is strongly affected by solar radiation, which ionizes the atoms present in this region of the atmosphere during the day (hence its name). The ionosphere plays an important role in the propagation of certain radio waves by reflecting them beyond the horizon, but it can also disrupt GPS signals and therefore distort the location of users.
During a total solar eclipse, the part of the ionosphere that is temporarily inside the shadow cone created by the Moon is suddenly deprived of ionizing radiation coming from the Sun. This provides researchers with a unique opportunity to study the ionosphere and its response to sudden changes in solar radiation.
To do this, scientists will use various instruments, such as sounding rockets that will pass through the ionosphere at the time of totality, GPS receivers and radar systems, to measure ionospheric variations during the eclipse, which will allow us to improve our understanding of the dynamics of this important part of the Earth’s atmosphere and its link with radiation from the Sun.
Animal behavior
Several research teams, in the United States and here in Quebec, at the Granby Zoo, will observe the behavior of animals during the eclipse. Observations will also take place a few days before and after the event, in order to establish a basis for comparing their “usual” behaviors with what they will do during the event.
Given the rarity of eclipses above a given location, this type of study is infrequent, but promises to teach us more about the behavior of animals in “unusual” situations, which could allow us to better understand how some of the species studied perceive the world around them.
On this subject, moreover, the public is invited to participate in citizen science projects led by NASA as well as by Adam Hartstone-Rose and his team at North Carolina State University. In the case of NASA, the public is invited to record the sounds of nature during the eclipse in order to highlight changes that could be linked to this astronomical phenomenon.
Adam Hartstone-Rose’s team launched the Solar Eclipse Safari project aimed at collecting behavioral data from pets, farm animals or animals living close to humans (such as birds that live near feeders, for example) during the eclipse.
Although the documentation is only available in English, Quebecers are invited to participate in large numbers in this research project, and the author of these lines has it on good authority that Adam Hartstone-Rose would personally be delighted to receive data compiled in the language of Molière!