By Jonny Lupsha, News Editor
A near-total solar eclipse has hit parts of North America. Residents of the northeastern United States, Canada and Greenland witnessed the fiery spectacle early Thursday morning. Solar eclipses occur in stages and show us rare parts of the Sun.
A ring of the Sun’s surface surrounded the Moon during an annular solar eclipse on Thursday. At the time of the occurrence, the Moon was too far from Earth to completely obliterate the Sun during a total solar eclipse, but this produced a dramatic “ring of fire” effect for many residents and visitors north of the United States. Annular solar eclipses only happen once a year or every two years, making them quite a sight to see.
Solar eclipses occur by an intriguing coincidence of the size of the Moon and the distance of the Earth from the Sun. In his video series Sky Observation: Seeing and Understanding Cosmic WondersDr. Alex Filippenko, professor of astronomy at the University of California, Berkley, explained the stages of a total solar eclipse from first contact to totality, as well as annular eclipses.
Everything under the sun is in harmony
“As the Moon orbits the Earth and moves west to east relative to the sky background, it first begins to cover the part of the Sun that faces west,” Dr Filippenko said. “This moment is known as first contact, and eclipse viewers scream for joy when they detect it. The whole thing is on its way with only about an hour to go.
Soon, it appears that a significant portion of the Sun has been bitten off, although the brightness of the daytime sky does not change until more than half of the Sun is obscured. It’s subtle enough that most people wouldn’t notice if they weren’t looking at the Sun. However, once the Sun is about 3/4 of which is covered, things change quickly and dramatically.
“Right before the totality, you see the amazing ‘diamond ring’ effect,” said Dr Filippenko. “The last little part of the Sun discovered [is] like a brilliantly brilliant diamond against the darkening sky very, very quickly. You can see the chromosphere and the inner corona start to come around the edge of the Moon.
“In another moment, it will be what is called the ‘second contact’, when the eclipse is finally total.”
The Sun is eclipsed by the Moon
Images of annular eclipses can confuse most of the audience because they look so much like total solar eclipses. In fact, the difference between the two is minor, but distinct.
“The Moon’s orbit is an ellipse, like a squashed circle,” Dr. Filippenko said. “The Earth is moved from the center of the ellipse by about 6%; this means that at the closest approach to Earth, the Moon is about 12% closer than at its farthest, and therefore it appears 12% larger. When the Moon is further away than the Earth’s average, it does not appear as large as when it is close, and therefore it is not large enough to completely block the Sun’s photosphere.
“We get an annular eclipse instead of a total eclipse.”
Simply put, it may appear that the Sun is completely eclipsed by the Moon, but the Moon is so far away that too much of the Sun’s photosphere is still visible around the Moon to count as a total eclipse. .
However, as many in North America saw on Thursday, the “Ring of Fire” is still a sight to behold.
Edited by Angela Shoemaker, The Great Courses Daily