The third and final solar eclipse of 2019 will be witnessed on July 2, 2019. The eclipse dubbed as the “Great South American Eclipse” will be the only total solar eclipse of 2019. It will be visible to millions of people in South America, especially people in Chile and Argentina witnessing the total eclipse. Neighbouring countries will be able to see a partial eclipse.
If you happen to be in the path of totality you may want to use this rare opportunity to observe these stars and planets that are not otherwise visible during daytime.
How does a Solar Eclipse Occur?
When the moon gets between Earth and the sun, the moon casts a shadow over Earth causing what we call the Solar Eclipse.
A solar eclipse can only occur at the phase of new moon when the moon passes directly between sun and Earth and its shadow falls upon the Earth’s surface.
It depends upon several factors, whether the alignment of moon will produce an annular solar eclipse or total solar eclipse.
Total Solar Eclipse
You may call a total solar eclipse a perfect accident of nature or the result of divine intervention, but the conditions that lead to a total solar eclipse are nothing short of intriguing.
The sun having a diameter of 1.391 million kilometers (864,000 miles) is 400 times greater than the moon which is just about 3,474 kilometers (2160 miles). But the moon is also 400 times closer to Earth than the sun (variation of this ratio occurs as both the orbits are elliptical) making it appear almost the same size as the sun. When the orbital planes intersect and there is favourable alignment of distances, the new moon appears to completely obscure the disk of the sun.
A total solar eclipse occurs on Earth in about every 18 months.
The eclipse casts two types of shadows on earth :
Umbra can be observed to have the shape of a dark, slender cone surrounded by the penumbra, which is a lighter, funnel-shaped shadow from which sunlight is partially obscured.
During a total solar eclipse, the moon casts its umbra upon the Earth’s surface; the shadow can sweep a third of the way around the planet in just a few hours. People fortunate enough to be in the direct path of the umbra will see the sun’s disk diminish into a crescent as the moon’s dark shadow rushes towards them in the landscape.
In the brief period of totality, when the sun is completely covered, the beautiful beautiful corona – the tenuous outer atmosphere of the sun, is revealed.
Totality may last as long as 7 minutes 31 seconds, though most total solar eclipses are shorter.
Partial Solar Eclipse
A partial solar eclipse occurs when only the penumbra ( or partial shadow) is incident on you. A part of the sun always remains in view in case of a partial solar eclipse. However, it depends on specific circumstances how much of the sun remains in view.
The closer you are to the path of totality, the greater the solar obscuration. For instance, if you are positioned just outside the path of the total solar eclipse, you will see the sun wane to a narrow crescent, then thicken up again as the shadow passes by.
Annular Solar Eclipse
The famously called “ring of fire” is what we see during an annular solar eclipse. It is similar to a total eclipse in that the moon appears to pass centrally across the sun. However, the moon is too small to cover the disk of the sun entirely.
Due to the moon circling Earth in an elliptical orbit, its distance from Earth can vary from 221,457 miles to 252,712 miles. But the dark shadow of the moon’s umbra can extend out for no longer than 235,700 miles; which is lesser than than the moon’s average distance from Earth.
So, if the moon is at some greater distance owing to its orbital shape, the tip of the umbra does not reach Earth. In the course of such an eclipse, the antumbra – a theoretical continuation of the umbra, reaches the ground, and anyone situated within it can see past either side of the umbra and observe an annulus.
Hybrid Solar Eclipses (“A-T” Eclipses)
These are also known as annular-total (“A-T” eclipses). Such eclipses occur when the moon’s distance is near its limit for the umbra to reach the Earth. An A-T eclipse, in most cases starts as an annular eclipse as the tip of the umbra falls just short of reaching Earth; it becomes total, as the the roundness and of the planet catches up and intercepts the shadow tip near the middle of the path, then it returns to annular towards the end of the path.
The total, annular and hybrid solar eclipses are generally called “central” eclipses to differentiate them from partial eclipses, as in these cases the moon appears to pass directly in front of the sun.
Where can the Eclipse be Seen?
The path of totality, where skywatchers can see the total solar eclipse, is a 200 kilometers wide (125 miles) strip of landing starting near La Serena, Chile and ending just south of Buenos Aires, Argentina. A partial eclipse will be visible in Uruguay, Paraguay, Ecuador and Brazil.
Most of the eclipse will occur over the Pacific Ocean without much of an audience, but it will end with a spectacular sunset on the east coast of South America.
Not in the path of totality? You can live stream the eclipse here.
You can check out what your view of the eclipse will look like from a specific location in this interactive map.
The moon will first appear to make contact with the sun above the Pacific Ocean at 12:55 p.m. EDT, 10:25 p.m. IST (1655 GMT). This will be the beginning of the partial phase of the eclipse.
Totality will first be seen over Oeno Island, a British territory in the South Pacific Ocean, at 10:24 a.m. local time, 11:55 p.m. IST (1824 GMT). This first place in South America to see totality will be near La Serena, Chile, where totality begins at 4:39 p.m. local time (1939 GMT). Before that, La Serena will see a partial eclipse for over an hour as skywatchers there eagerly await totality.
The table below shows the start, peak and end times of the eclipse for a few cities in and around the path of totality. For places that will see only a partial eclipse, the table lists as well as the maximum obscuration, or the percentage of the sun’s disk that will be covered by the moon.
Observing the Eclipse Safely
We have been told many times growing up, not to stare at the sun or it could amage our eyes. The same rule applies during solar eclipse too. But, during the totality, when the sun is completely hidden from view, you can remove your eclipse glasses and have a look at the sun’s beautiful corona. This is the only time that it is safe to look at the sun without proper eye protection.
Here is a gallery of beautiful images taken by NASA of the 2017 total solar eclipse that occured on August 21.