A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth’s surface. But whether the alignment produces a total solar eclipse, a partial solar eclipse or an annular solar eclipse depends on several factors, all explained below.
The fact that an eclipse can occur at all is a fluke of celestial mechanics and time. Since the moon formed about 4.5 billion years ago, it has been gradually moving away from Earth (by about 1.6 inches, or 4 centimeters per year). Right now the moon is at the perfect distance to appear in our sky exactly the same size as the sun, and therefore block it out. But this is not always true.
The next solar eclipse will be a partial solar eclipse on April 30, 2022. It will be the first of two partial solar eclipses in 2022; the second will occur on Oct. 25. We won't see another total solar eclipse until 2023.
The April 30 eclipse will only be visible from parts of Antarctica and the southern tip of South America, as well as parts of the Pacific and Atlantic oceans.
There are four types of solar eclipses: total, partial, annual and hybrid. Total solar eclipses happen when the sun is completely blocked by the moon.
- Partial solar eclipses occur when the Moon only partially obscures the Sun's disk and casts only its penumbra on Earth.
- Annular solar eclipses take place when the Moon's disk is not big enough to cover the entire disk of the Sun, and the Sun's outer edges remain visible to form a ring of fire in the sky. An annular eclipse of the Sun takes place when the Moon is near apogee, and the Moon's antumbra falls on Earth.
- Total solar eclipses happen when the Moon completely covers the Sun, and it can only take place when the Moon is near perigee, the point of the Moon's orbit closest to Earth. You can only see a total solar eclipse if you're in the path where the Moon casts its darkest shadow, the umbra.
- Hybrid Solar Eclipses, also known as annular-total eclipses, are the rarest type. They occur when the same eclipse changes from an annular to a total solar eclipse, and/or vice versa, along the eclipse's path.
How many eclipse are there?
There are two complete eclipse seasons, one at each node, during a calendar year. Because there is a new moon every month, at least one solar eclipse, and occasionally two, occurs during each eclipse season.
7.5 minutes is the longest duration for a total solar eclipse.
Solar Eclipse 101 | National Geographic
August 17, 2017