A total solar eclipse will pass over North America on Monday, offering millions of people a rare opportunity to see the afternoon sky temporarily darken as the moon blocks the sun’s face.
The eclipse’s path coincidentally passes Mexico, 15 U.S. states and a small portion of eastern Canada. Viewers in all other states in the continental U.S. will be treated to a partial solar eclipse, where the moon appears to take a bite out of the sun and obscures some of its light.
Here’s everything you need to know about the rare celestial event.
What is a solar eclipse?
Solar eclipses occur when the Sun, Moon and Earth are aligned. The Moon passes between the Earth and the Sun, temporarily blocking the Sun’s light and casting a shadow on the Earth.
A total solar eclipse means the moon completely blocks the sun, while a partial solar eclipse means it only covers part of the sun’s face.
Solar eclipses only occur with the new moon. Because the Moon’s orbit around the Earth is tilted, the three objects do not always line up to form an eclipse.
“Imagine if the Moon’s orbit were in the same plane as the Earth’s orbit around the sun; if that were the case, there would be a total solar eclipse every new moon, and a lunar eclipse every full moon.” “So it adds to the rarity and specialness of the event because not everything is always aligned,” Neil DeGrasse Tyson, director of the Hayden Planetarium at the American Museum of Natural History, told NBC News.
Where and when will the eclipse be seen?
This year’s eclipse will follow a slightly wider path across more populated parts of the continental United States than other total solar eclipses in recent memory.
NASA estimates that 31.6 million people live in the area known as the path of totality, where a total solar eclipse can be seen. Another 150 million people live within 200 miles of the road, according to the agency.
The road passes through Texas, Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire and Maine. If conditions are clear, small parts of Michigan and Tennessee will also be able to witness totality.
After crossing into Canada, the eclipse will cross the eastern tip of Nova Scotia, passing southern Ontario, Quebec, New Brunswick, Prince Edward Island and Cape Breton.
Those outside the path of totality can still participate in the astronomical event by viewing the partial solar eclipse or NASA livestream, which will be visible in all 48 contiguous US states.
Timing, including how long totality lasts, depends on location, but at some points the moon will appear to completely cover the sun for up to 4 minutes and 28 seconds.
Below is a list of timings of some cities along the path of totality provided by NASA. A number of other resources, such as NationalEclipse.com and TimeandDate.com, can also help people plan.
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Dallas: Partial eclipse begins at 12:23 PM CT and total eclipse begins at 1:40 PM
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Little Rock, Arkansas: Partial eclipse begins at 12:33 PM CT and total eclipse begins at 1:51 PM
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Cleveland: Partial eclipse begins at 1:59 PM ET and total eclipse begins at 3:13 PM
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Buffalo, New York: Partial eclipse will begin at 2:04 PM ET and total eclipse will begin at 3:18 PM
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Lancaster, New Hampshire: Partial eclipse will begin at 2:16 PM ET and total eclipse will begin at 3:27 PM
How to watch a solar eclipse safely
It is never safe to look directly at the sun, even if it is partially or mostly obscured by the moon. Special eclipse glasses or pinhole projectors are required to view solar eclipses safely and prevent eye damage. Failure to take proper precautions can cause serious eye injuries, according to NASA.
Eclipse glasses are thousands of times darker than normal sunglasses and are specially made so that users can look at the sun during such celestial events.
Skywatchers should never view any part of the sun through binoculars, telescopes, or camera lenses unless special solar filters are installed. Eclipse glasses should not be used with these devices as they may not provide adequate protection.
However, it is safe to look with the naked eye during the few minutes of totality, when the moon completely blocks the sun.
Beware of fake solar eclipse glasses. In legitimate couples, the front of the lenses should be silver and the inside should be black. The manufacturer’s name and address must be clearly labeled and must not be torn or punctured. Also check for the ISO logo and the code “IS 12312-2” written on the inside.
If you don’t have eclipse glasses, you can make a homemade pinhole projector that lets sunlight in through a small hole, focuses it, and projects it onto a piece of paper, wall, or other surface, creating an image of the sun. It’s safe to look at.
All you need is two pieces of white cardstock or plain white paper, aluminum foil, and a tack or thumbtack. Cut a square or rectangle 1 to 2 inches from the center of a piece of white paper or cardboard. Tape aluminum foil over the cut shape, then use a pin or pushpin to poke a small hole in the foil.
During the eclipse, place a second piece of white paper or cardboard on the floor as a screen and hold the projector with the foil facing up and your back facing the sun. Adjusting how far you hold the projector from the second piece of paper will change the size of the temporary on-screen image.
What should you pay attention to when watching a total solar eclipse?
For people on the path to totality, there are some fun milestones to keep track of as the total solar eclipse occurs.
According to Tyson, as the eclipse progresses and the sun thins out in the sky, the sky will begin to get eerily dark.
Watch out for the “diamond ring effect” as the last rays of sunlight are about to darken: the Sun’s atmosphere will appear like an illuminated halo, and the last light still visible will look like the diamond of a giant ring.
As sunlight decreases further, the Moon’s rugged terrain will create an effect known as Baily beads. Tiny “beads” of light will be visible around the dark moon for only a few seconds as the last bits of sunlight pass through the moon’s mountains and valleys.
When the moon completely blocks the sun, it is safe to remove the eclipse glasses and look at the total solar eclipse with the naked eye.
Some lucky sky watchers may even spot a comet.
Comet 12P/Pons-Brooks, nicknamed the “devil comet” because its explosion last year left two distinctive devil horn-shaped trails of gas and ice, is currently visible from the Northern Hemisphere as it swings across the inner solar system. .
The comet can be seen looking toward the west-northwest horizon in the early evening. During the eclipse, when the sky darkens during totality, it may be possible to see the comet near Jupiter, but its visibility will depend on whether it is in the middle of an outburst and therefore brighter than usual.
Most likely all eyes will be in line with the moon and the sun.
“Most people won’t even notice,” Tyson said. “But if you know how to look, it’s there.”
When is the next solar eclipse?
The next total solar eclipse will occur in 2026, but will pass mostly over the Arctic Ocean with some visibility in Greenland, Iceland, Portugal and northern Spain. In 2027, a total solar eclipse will be visible in Spain and part of North Africa.
The next total solar eclipse visible from North America will occur in 2033, but only over Alaska. Then in 2044, a total solar eclipse will pass over Montana, North Dakota, South Dakota, parts of Canada, and Greenland.
The next total solar eclipse that will cross the continental United States from coast to coast will occur in 2045. The totality path of this eclipse will pass through California, Nevada, Utah, Colorado, New Mexico, Oklahoma, Kansas, Texas, Arkansas. Missouri, Mississippi, Louisiana, Alabama, Georgia and Florida.
This article first appeared on NBCNews.com.