History of eclipses through a camera lens

The IAFE and the Institute of Astrophysics in Paris have organized an itinerant photo exhibition in collaboration with the Embassy of France in Argentina.

Guillaume Herbrard and Rodrigo Díaz. Photo: CONICET Photography/ Verónica Tello.

Within the Framework of an International project of French and Argentine collaboration to study exoplanets financed by the Centre national de la recherche scientifique (CNRS), the Argentine Institute of Space Physics (IAFE, CONICET-UBA) and the Institute of Astrophysics of Paris (IAP) organized an itinerant photo exhibition on solar eclipses that will be available up to July 14th in the Galileo Galillei Planetarium of Buenos Aires and since yesterday is also present at the Civic Center of San Juan.

The trigger of this proposal, which is expected to be in all the country, is the two solar eclipses that will take place in Argentina between 2019 and 2020 (the first of them, yesterday at 17:40 and the following one on December 14th at noon). Rodrigo Díaz, CONICET associate researcher at the IAFE and Guillaume Herbrard of the IAP are the scientific curators of the exhibition that has panels of experts destined to historical eclipses and pictures of eclipses taken by professional and amateur photographers of France and Argentina.

What is a solar eclipse?

Guillaume Herbrad: a solar eclipse occurs when from the perspective of the Earth, the Moon interposes the Sun. It can be partial if only one part of the Sun is covered and total if it is covered completely. A total solar eclipse is an extraordinary natural event that involves a sudden nightfall in daylight. It is really striking to observe the crown of the Sun -the external part of the solar atmosphere- which is impossible to see in other conditions.

Which are characteristics of this eclipse?

GH: It is going to be partial in all Argentina but within a band of approximately 140 kilometers wide, which goes from downtown San Juan up to the north of the province of Buenos Aires passing through the north of San Luis and the south of Córdoba and Santa Fe, the eclipse will be total. Something similar is going to take place next year on December 14 as there is going to be a total eclipse in some parts of Neuquén and Río Negro, with the advantage that it will happen at a time when the Sun is going to be higher, what will make its observation more impressive.

How does this astronomic phenomenon take place?

Rodrigo Díaz: To understand how it occurs, it is necessary to take into account three bodies: the Moon, the Sun, and the Earth. Both the Moon and the Earth receive sunlight. The arrival of light on Earth marks days and nights, while its effect on the Moon determines the different phases it goes through during the month it takes his return to the Earth (Fourth waning, New Moon, Crescent, Full Moon). Once a month, if we see it from our planet, the Moon is in the same direction as the Sun, but in general it passes above or bellow, so eclipses do not occur very month. But every so often it crosses the disk of the Sun and then an eclipse takes place.

How is a total solar eclipse different from the one that was seen in Argentina on February 26, 2017?

RD: A total solar eclipse occurs when the Moon is at such a distance from the Earth that makes our planet look larger than the Sun from our perespective (it is actually 400 times smaller) so in a certain strip of our planet its light is covered completely. During the annular eclipses, the Moon is at a greater distance, so when aligning with the Sun (always from our perspective), it does not cover it but forms a ring of light. As with total eclipses, outside a determined territorial range, annular eclipses are also seen as partial eclipses.

By Miguel Faigón