The first solar eclipse of 2016 occurred on March 8/9 and is the only total solar eclipse of the year. Learn more about that event below. The next one will be an annular solar eclipse (also known as a "ring of fire" solar eclipse) on Sept. 1, 2016.
This photo of the partial solar eclipse of Sept. 13, 2015, was snapped by astrophotographer K.J. Mulder from his home in South Africa.
Credit: K.J. Mulder/Worlds in Ink
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 last solar eclipse was a total eclipse on March 20, 2015. [Related: Spectacular Solar Eclipse Kicks Off Spring]
The next one will be a total solar eclipse on March 9, 2016 . According to Geoff Gaherty of Starry Night Education, the moon will be close to perigee for this eclipse, leading to a long period of totality, just over four minutes. The eclipse will begin over the Indian Ocean, and the moon’s shadow first makes landfall on the island of Sumatra, Indonesia.
It then passes over Borneo, Sulawesi and Halmahera, before heading out into the Pacific Ocean, ending north of Hawaii. The partial eclipse will be visible over southern and eastern Asia, northern and western Australia, and much of the Pacific, including Hawaii. The times of maximum eclipse at major cities (Universal Time):
On Sept. 1, 2016, an annular eclipse will be visible over most of Africa, the southern Arabian Peninsula, and much of the Indian Ocean. Maximum eclipse occurs in Antarctica at 09:07 UT.
There are four types of solar eclipses: total, annular, partial and hybrid. Here’s what causes each type:
Total solar eclipses
These are a happy accident of nature. The sun's 864,000-mile diameter is fully 400 times greater than that of our puny moon, which measures just about 2,160 miles. But the moon also happens to be about 400 times closer to Earth than the sun (the ratio varies as both orbits are elliptical), and as a result, when the orbital planes intersect and the distances align favorably, the new moon can appear to completely blot out the disk of the sun. On the average a total eclipse occurs somewhere on Earth about every 18 months.
There are actually two types of shadows: the umbra is that part of the shadow where all sunlight is blocked out. The umbra takes the shape of a dark, slender cone. It is surrounded by the penumbra, a lighter, funnel-shaped shadow from which sunlight is partially obscured.
During a total solar eclipse, the moon casts its umbra upon Earth's surface; that shadow can sweep a third of the way around the planet in just a few hours. Those who are fortunate enough to be positioned in the direct path of the umbra will see the sun's disk diminish into a crescent as the moon's dark shadow rushes toward them across the landscape.
During the brief period of totality, when the sun is completely covered, the beautiful corona — the tenuous outer atmosphere of the sun — is revealed. Totality may last as long as 7 minutes 31 seconds, though most total eclipses are usually much shorter.
On Jan. 4, 2011, the moon passed in front of the sun in a partial solar eclipse - as seen from parts of Earth. Here, the joint Japanese-American Hinode satellite captured the same breathtaking event from space. The unique view created what's called an annular solar eclipse.