Solar Eclipse

The moon’s orbit around the Earth is not a perfect circle, but an ellipse. When the moon is closest to the Earth, it appears slightly larger in the sky than it does when it is furthest away. This can make a difference during a solar eclipse. If a solar eclipse occurs during the part of the moon’s orbit when it’s at its farthest point, then the apparent size of the moon is not big enough to fully cover the sun’s disk, as it does during a total solar eclipse. In this case, there will still be a ring of sunlight — a “ring of fire” — visible around the moon. This is called an annular solar eclipse (annulus means “ringed shaped”), and the path of the moon’s shadow across the Earth is called the path of annularity. As with a total eclipse, the closer you are to the center of the path, the longer annularity will last. During the Oct. 14, 2023, annular eclipse, the whole event will take about 3 hours, but annularity will only last about 5 minutes, depending on your location.

Safety first: If you want to view the sun during an annular eclipse, you must wear protective solar eclipse glasses during the entire event.

 

There are two categories of partial eclipses. First, all total and annular solar eclipses begin and end with a period of partial eclipse. Also, viewers outside the path of totality or annularity experience only a partial eclipse. How an eclipse appears — how much “bite” is taken out of the sun — depends on how far away the viewer is from the path of totality.

It’s all due to geometry and shadows. Objects illuminated by the sun — including the moon — cast two shadows. This is because the sun is not a point source of light — it takes up half a degree in the sky. The moon casts two cone-shaped shadows. For anyone inside the smaller, darker shadow, called the umbra, the sun will be completely blocked during a total solar eclipse. The second, larger shadow — called the penumbra — is also a cone. Anyone who is in the penumbral shadow will experience only a partial blockage of the sun by the moon.

A partial eclipse also can occur when the moon, sun and Earth don’t line up perfectly, but are close enough to alignment that the outer part of the moon’s shadow — the penumbra — falls on the Earth while the darkest shadow — the umbra — misses Earth. Anyone who is in the penumbral shadow will experience a partial blockage of the sun by the moon.

Safety first: If you want to view the sun during any partial eclipse, you must wear protective solar eclipse glasses the entire time.

The orbit of the moon is tilted about 5 degrees relative to the orbit of the Earth around the sun. As a result, most of the time, the moon, sun and Earth are not directly lined up with one another, and the moon’s shadow falls completely above or below Earth. Watch this visual explanation.

Total solar eclipses occur, on average, every 18 months, and annular eclipses occur every one to two years. From a given place on Earth, however, a total or annular eclipse is extremely rare, occurring roughly about every 300 to 400 years. The last time a total solar eclipse was visible anywhere in Texas was on July 29, 1878.

Time and Date AS features time-lapse animations of what solar and lunar eclipses will look like from any location on Earth. The animations provide the exact start and end times as well as the duration of totality or annularity.

View this path of annularity. The center line in the path is where the annularity will last the longest.

View this path of totality. The center line in the path is where the totality will last the longest.

Eclipses occur when the sun, moon and Earth are lined up in roughly a straight line — in astronomy, such an alignment between three or more bodies in a gravitational system is called syzygy. The type of eclipse depends on the order of the bodies in the alignment.

Solar eclipses, which occur only during the day, happen when the moon is between the sun and the Earth, and the moon’s shadow passes over the Earth.

A lunar eclipse occurs only at night, when the Earth is between the sun and moon. During a lunar eclipse, the Earth’s shadow falls on the moon.

For more information, watch this solar eclipse video.

As the moon passes into and out of the Earth’s shadow during a lunar eclipse, the moon appears to change color. Because the Earth is so much larger than the moon, its shadow is also large enough to cover the entire moon. During a total lunar eclipse, the moon appears orange or reddish.

Unlike a total solar eclipse, where you must be located in the narrow path of the moon’s shadow to experience totality, essentially everyone on the nightside of the Earth can see the moon during a lunar eclipse.