Skywatchers in North America will be in for a treat Thursday morning as an annular “ring of fire” solar eclipse will be visible in portions of Canada while a partial solar eclipse will be seen as the sun rises across much of the northeastern U.S.
On June 10, the ring of fire will be visible across a narrow band in the far northern latitudes, starting near Lake Superior in Ontario, Canada, at sunrise, or 5:55 a.m. Eastern time. It will then cross Greenland, the Arctic Ocean and the North Pole, ending in Siberia at sunset, or 7:29 a.m. Eastern time.
Outside of that strip, observers will see a crescent sun, or a partial solar eclipse. The closer they are to the centerline, the more of the sun will be gone. In the New York metropolitan area, said Mike Kentrianakis, who was the Eclipse Project Manager for the American Astronomical Society during the big eclipse in 2017, the sun will be about two-thirds obscured when it rises at 5:25 a.m. Eastern time.
“It will then reach a maximum obscuration of nearly 73 percent at 5:32 a.m. from New York City,” he wrote in an email.
He added: “Expect an exceptionally darkened dawn. It’s always darkest before dawn. On this morning not exactly!”
How often do different types of solar eclipses occur and why? Why don’t you see one every time there’s a new Moon? Has their frequency changed over time?
Solar eclipses, when the Moon totally or partially blocks out the Sun, still seem to many people a random and almost magical phenomenon, but they can be very accurately predicted, says Fred Espanak, an American astrophysicist and world authority on eclipses.
“Certainly within 100 to 200 years we can predict when an eclipse will occur to within a second,” Dr Espenak says, “but the pattern of occurrence is a complicated one”.
“They don’t repeat on a time schedule like the seasons of the year,” he adds.
There are four types of eclipse: total, annular, partial and hybrid.
Dr Espanak says an average of 2.4 solar eclipses occur every year.
He has calculated when and where these eclipses will happen around the world up until 2030.
Eclipses occur during the new Moon phase of the Moon’s cycle, when it passes between the Earth and the Sun.
Total and annular eclipses
“With a total eclipse the darkest part of the Moon’s shadow sweeps across the Earth’s surface and if you happen to be in the path of that very small shadow, usually 100 to 200 kilometres’ diameter, you will see the Moon completely block the Sun’s disc,” Dr Espenak explains.
“Total solar eclipses occur once every one to two years but are only visible from less than half a per cent of the Earth’s surface”.
Whether an eclipse is total, when the Sun is completely blocked with just a halo of light appearing around it, or annular, when the moon appears smaller and is silhouetted against the Sun, depends on which point of its orbit the moon is in at the time.
“Total eclipses occur along the section of the moon’s orbit called perigee, where the Moon is closest to the Earth,” Dr Espenak says.
“At the other end of the Moon’s orbit, called apogee, the Moon is further from the Earth and appears smaller than the Sun.”
Partial and hybrid eclipses
Similar in frequency to the annular eclipse but, according to Dr Espenak, much less interesting to eclipse fans, is the partial eclipse.
“In that case the Moon’s central shadow completely misses the Earth and you only get the outer edge of the shadow, the penumbral shadow, and during that type of eclipse you see the moon move along either the top or bottom edge of the Sun but not through the middle of the Sun,” he says.
Rarest of all is the hybrid eclipse, Dr Espenak says.
The most recent hybrid eclipse, in 2013, was visible from parts of America, Europe and Africa, the next will not happen until April 20, 2023 and will be seen from parts of Australia and Southeast Asia.
“The Moon’s orbit is elliptical so if you happen to get a solar eclipse just as the Moon’s distance is changing from a little bit smaller than the Sun to a little bit larger than the Sun, what you can get is an eclipse path that begins as annular and ends up total, or vice versa,” he says.
Dr Espenak says the frequency of eclipses hasn’t changed in thousands of years, and only immensely slow geological factors like the very gradual slowing of the Earth may make them difficult to predict many thousands of years from now.
Why not every New Moon?
So why do we not see an eclipse every time there is a new Moon?
“Because the Moon’s orbit is tipped about 5 degrees to the Earth’s orbit around the Sun,” Dr Espenak says.
“During most new Moons when the Moon passes between the Earth and the Sun, the Moon’s orbit takes it a little bit above the plane of the Earth’s orbit or a little bit below the plane of the Earth’s orbit and what that means is you see the Moon passing a little bit above the Sun or a little bit below the Sun, but at least twice a year we get some type of a solar eclipse.
Is eye protection necessary during the eclipse?
Yes, absolutely! “It is never safe to look directly at the sun’s rays – even if the sun is partly obscured,” NASA warned. “When watching a partial eclipse you must wear eclipse glasses at all times if you want to face the sun or use an alternate indirect method.”
Solar eclipse glasses must be worn at all times during an annular or partial solar eclipse to avoid the threat of blindness, so it can be a dangerous event if you’re not properly prepared. NASA warns to never look directly at the sun: It can permanently damage your eyes.
“It is only during the total phase of a total eclipse that it is completely safe to view the sun with the naked eye,” said eclipse chaser Fred Espenak, a retired NASA astrophysicist.
If you still have eclipse glasses around from the big 2017 “Great American Eclipse,” they should be fine for viewing Thursday’s eclipse, as long as they’ve been stored properly.
Can I watch this eclipse online?
There are a number of options to watch a stream of the eclipse.
NASA will start its video coverage on YouTube at 5 a.m. Eastern time, although the agency says that the view will be dark until 5:47 a.m.