By Jonny Lupsha, Wondrium Staff Writer
A near-total solar eclipse shone down on parts of North America. Residents of the northeast United States, Canada, and Greenland caught 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 in an annular solar eclipse on Thursday. At the time of the event’s occurrence, the Moon was too far from Earth to completely blot out the Sun in a total solar eclipse, but it did produce a dramatic “ring of fire” effect for many residents and visitors north of the United States. Annular solar eclipses only occur once every year or two, making them a true sight to behold.
Solar eclipses occur by an intriguing coincidence of the Moon’s size and Earth’s distance from the Sun. In his video series Skywatching: Seeing and Understanding Cosmic Wonders, Dr. 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 Tune
“As the Moon orbits Earth and goes from west to east relative to the background sky, it first starts to cover the part of the Sun that faces west,” Dr. Filippenko said. “This moment is known as first contact, and eclipse viewers shout out with glee when they detect it. Totality is on its way with only about an hour to go.”
Soon, it looks like a sizeable chunk of the Sun has had a bite taken out of it, though the brightness of the daytime sky doesn’t change until more than half of the Sun is obscured. It’s subtle enough that most people wouldn’t notice it were they not looking at the Sun. However, once the Sun is about 3/4 covered, things change quickly and drastically.
“Just before totality, the stunning ‘diamond ring’ effect is seen,” Dr. Filippenko said. “The last tiny part of the uncovered Sun [is] like a blazingly bright diamond compared with the very, very rapidly darkening sky. You can see the chromosphere and the inner corona start to come around the Moon’s edge.
“In another moment, it will be what’s called ‘second contact,’ when the eclipse is finally total.”
The Sun Is Eclipsed by the Moon
Pictures of annular eclipses may confuse most of the public since 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 displaced from the center of the ellipse by about 6%; this means that at closest approach to Earth, the Moon is roughly 12% closer than at its farthest, and so it looks 12% bigger. When the Moon is farther than average from Earth, it doesn’t appear as big as when it is close by, and so it is not big enough to fully block the Sun’s photosphere.
“We get an annular eclipse instead of a total eclipse.”
Put simply, it may look like the Sun is fully 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 for it to count as a total eclipse.
However, as many in North America saw Thursday, the “ring of fire” is still a sight to behold.