(CNNMéxico) - On Sunday, May 20, an annular solar eclipse will be visible from some areas of United States, northern Mexico and Canada, according to the Institute of Astronomy, in the Universidad Nacional Autónoma de México (UNAM, Autonomous National University of Mexico).
"Solar eclipses occur when the moon covers the solar disk and projects its shadow on Earth," the Institute explained on its website.
A solar eclipse happens when the moon is in its new moon phase and is perfectly aligned with both the sun and the Earth. From our perspective, the sun is hidden.
During the astronomical phenomenon on May 20, the moon will be in one of its furthest positions from Earth, so its shadow will not be able to completely hide the sun, as would occur in a total eclipse.
That's why this phenomenon is called an annular eclipse. "For this beautiful phenomenon, the sun peeks over the edges of the moon as a bright shining ring," according to the Institute.
"In the United States, the afternoon sun will become a luminous ring in places such as Medford, Oregon; Chico, California; Reno, Nevada; St. George, Utah; Albuquerque, New Mexico, and Lubbock, Texas," according to NASA.
Other locations where partial phases of the eclipse will be visible include Alabama, Idaho, Kentucky, Oklahoma, Illinois, Missouri and New York. You can see the complete list of cities here (pdf).
If you are going to watch this annular eclipse, be careful not to look at the sun directly.
According to UNAM, although the area where you can observe the eclipse in its annular phase does not pass through Mexico, it will be partially visible in the northwest part of the country.
It will cover from 80% of the solar disk in Ciudad Juarez (Chihuahua), Tijuana and Mexicali (Baja California); up to 70% in the city of Chihuahua (Chihuahua) and Hermosillo (Sonora), and 60% in Cabo San Lucas, La Paz (Baja California Sur), Culiacan and Los Mochis (Sinaloa).
"The rest of Mexico will find difficulties to see the eclipse because the moon's first contact with the solar disk will be just minutes before the sun sets," said the Institute.
The estimated time for the start of the eclipse in the city of Chihuahua is at 17:37 hours in Ciudad Juarez, at 17:33 in Hermosillo, at 17:33 in La Paz, at 17:43 and in Tijuana at 16:28.
"This eclipse is the latest to pass through Mexico since the partial annular eclipse of April 8, 2005, visible in much of the country as partial," said the Institute of Astronomy.
The last total solar eclipse observed from Mexico was on June 11, 1991, recalled the scientific body.
The eclipse will also be visible in parts of China and Japan, according to NASA. "It's an annular solar eclipse, the last in the U.S. in nearly 18 years."
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