Finally, the day has arrived. The total solar eclipse that will sweep a wide strip of the north of the Peninsula and the Balearic Islands this Wednesday at sunset has unleashed a true eclipse mania, as for many people, it will be the first time they can enjoy this spectacular astronomical phenomenon. The last time it could be seen on the Peninsula was in 1912, and in the Canary Islands, in 1959. However, the 1912 eclipse was brief and affected little territory so not many people could enjoy it. The last one that a large number of people in Spain could see was in 1905, which was quite similar to today's, although longer: totality lasted almost four minutes.
In the regions where the solar eclipse will be total, the period of maximum darkness on August 12 will last between half a minute and one minute and 48 seconds. Only when the solar disk is completely hidden and the totality phase has begun can you look directly at the sky without the glasses for a few moments. The areas of Spain that will be outside of totality will see a partial eclipse, meaning the Moon will not completely cover the Sun so at no time can you look at our star without the protection of special glasses. On this website of the National Geographic Institute, you can check how and for how long it can be seen in the area where you are.
These are the key moments of this historic eclipse in the totality zone.
From around 7:30 p.m., the Moon will begin to cover the Sun little by little. The darkening process begins approximately an hour before totality. About 20 or 30 minutes before the concealment, the change in light is already noticeable, taking on a metallic hue.
As the solar disk decreases, the radiation it emits will also decrease, so the temperature will drop noticeably when there are 40 or 50 minutes left for totality. It will depend on the area, but it is usual for temperatures to drop between three and six degrees.
During the 10 minutes before the complete hiding of the Sun, our perception of colors may change due to the sudden drop in light, and the effects that the light transition causes in the retina. Our eyes quickly transition from a vision dominated by cones, typical of the day, to one in which rods also participate.
This causes bluish and greenish tones to appear brighter to us while reds seem to fade and darken, perceiving them as black. This phenomenon is called the Purkinje effect.
When there are only a couple of minutes left for the Sun to be out of our sight, we will see the lunar shadow, a kind of dark spot that our satellite projects onto the Earth's surface. We will feel that it is projected onto us.
It is one of the most anticipated moments, and it occurs just before totality - between 15 and 10 seconds before. Only a bright point remains visible, while the rest of the Sun disappears from our view. It is called this because the image may resemble a ring with a very bright diamond set in it. People who have seen a total solar eclipse describe this moment as spectacular, so capturing this instant is one of the goals of eclipse chasers. It is the last sign before totality begins and the solar corona reveals itself in all its splendor.
The diamond ring only lasts for one or two seconds, but we may see it fleetingly again when totality ends. Remember that during this phase, you should keep your eclipse glasses on.
Moments before totality - less than 10 seconds before - we will see how solar light filters through the lunar valleys, creating around our satellite a chain of bright points of light reminiscent of a luminous necklace made up of small bright beads suspended in space. Its name pays homage to the British astronomer Francis Baily, who first described this phenomenon during the solar eclipse of 1836. They are also called Baily's beads. During the diamond ring and Baily's beads phases, we may observe reddish or pinkish areas coming from the chromosphere, one of the layers of the Sun (the solar corona and the chromosphere make up the solar atmosphere).
Those reddish or pinkish colors are due to the emission of hydrogen (remember that the Sun is a large gas sphere composed mainly of hydrogen and helium).
The solar disk is completely hidden. We will only be able to see the solar corona, which is the outer part of our star. In this eclipse, this phase will begin between 8:28 p.m. and 8:31 p.m. approximately, depending on the area where we are, and will last between half a minute and one minute and 48 seconds.
Only in this phase could you take off the eclipse glasses to observe the Sun, although there are ophthalmologists who recommend not taking them off, or if you decide to do so, only for a few moments. Look around you, at the landscape and the people around you, and perceive the changes in colors, temperature, and the reaction of people and animals.
BAILY'S BEADS AND SECOND DIAMOND RING
When the totality phase ends, the Moon will start uncovering the Sun. From then on, we can experience in reverse the entire process leading up to totality. The Sun reappears with a bright flash. We will see again Baily's beads and the diamond ring with the pinkish tone of the chromosphere.
Between 8:30 p.m. and 9:30 p.m., the Moon will move away from the solar disk, so daylight will gradually return. As in much of the country, it will coincide with sunset, we will see a sunset with the Sun partially eclipsed.