A solar eclipse occurs when the Moon passes directly between the Sun and Earth, casting a shadow upon our planet and blocking the Sun’s light. These celestial alignments are common globally, but the path of the Moon’s shadow, known as the umbra, rarely tracks across the same geographical location. Understanding the history of these events in Pennsylvania helps clarify the rarity of experiencing a true total solar eclipse.
Identifying the Most Recent Major Eclipse
The last widely viewed solar eclipse across Pennsylvania before the 2024 event took place on August 21, 2017. This event, often called the “Great American Eclipse,” saw the Moon’s dark inner shadow, or umbra, sweep across the continental United States from Oregon to South Carolina. Pennsylvania was not located within this narrow track of totality, meaning residents experienced a significant partial solar eclipse instead of full darkness.
The magnitude of the partial eclipse varied across the state, but most regions saw a peak obscuration of the Sun’s disk ranging from 75% to 80%. For instance, in the southeastern part of the state, near Philadelphia, approximately 75% of the Sun’s area was covered by the Moon at maximum eclipse. While a substantial portion of the Sun was hidden, the remaining crescent remained intensely bright, preventing the sky from darkening completely to twilight levels. The partial eclipse began in the early afternoon, reached its maximum point around 2:44 p.m. EDT, and concluded shortly after 4:00 p.m. EDT.
Although a 75% obscuration is fundamentally different from a total eclipse, which causes the full day-to-night transformation. This 2017 alignment served as the last major celestial event to draw widespread public attention in Pennsylvania before the next significant occurrence.
The 2024 Event: Totality vs. Partiality in Pennsylvania
The solar eclipse of April 8, 2024, provided a much closer interaction with the Moon’s shadow for the state. This event featured a path of totality, where the Sun was completely blocked, that clipped the far northwestern corner of Pennsylvania. This narrow track, including the city of Erie, experienced the full celestial spectacle for approximately three minutes and forty-one seconds.
For the vast majority of the state’s population, the experience was a deep partial eclipse, distinct from the total event. Major metropolitan areas like Pittsburgh, Harrisburg, and Philadelphia fell outside the path of totality, only viewing the Moon covering between 90% and 97% of the Sun’s diameter. While this level of obscuration significantly dimmed the sky, it did not create the sudden, complete darkness or allow for the safe viewing of the Sun’s corona, which is the defining characteristic of totality.
The distinction between 99% partiality and 100% totality is significant, as even a tiny sliver of the Sun’s surface is powerful enough to keep the environment relatively bright. In the areas experiencing deep partiality, the light level was comparable to a heavily overcast day, rather than the sudden, eerie darkness of true totality. The Moon’s shadow raced across the state at speeds exceeding 2,100 miles per hour, making the experience brief for the few areas within the path.
Predicting the Next Total Solar Eclipse
The astronomical geometry required for the Moon’s umbral shadow to again track across a significant portion of Pennsylvania is a rare occurrence. While partial solar eclipses will continue to be visible with some frequency, the next total solar eclipse whose path of totality is projected to cross a major Pennsylvania population center is decades away. This next definitive event is predicted to occur on May 1, 2079.
The path of totality for the 2079 eclipse is currently forecast to include the city of Philadelphia, offering a full total solar eclipse experience for the eastern half of the state. The 2079 event offers the next opportunity to witness the Sun’s corona from a major city in the commonwealth.