Outside of it observers see only a partial cover-up. Annular eclipses of the Sun occur about as often as the total ones do, and an annular's path is likewise narrow. This geometric circumstance is known as an annular eclipse, so-called because you can see a ring, or annulus, of sunlight surrounding the lunar disk. (The Moon's orbit isn't perfectly circular its eccentricity is about 5%.) ![]() ![]() When that occurs, it's usually because the Moon is farther from Earth than its average distance. Occasionally the Moon passes directly in front of the Sun but doesn't completely cover it. Outside of that path, about half of the daylit hemisphere of Earth is able to watch a partial eclipse as the Moon obscures a portion of the Sun. Sky & Telescope / Kelly BeattyĪ completely eclipsed Sun can be viewed only from a narrow track or path on Earth's surface that's typically just 100 miles (160 km) wide. Here's how the corona looked during the total solar eclipse seen across the U.S. In November 2013, for example, planeloads of eclipse-chasers converged in a remote portion of northern Kenya to watch just 11 seconds of totality. With its brilliant disk completely covered, the Sun's ghostly white outer atmosphere is momentarily revealed for durations from seconds to several minutes. If the Moon completely hides the Sun, the eclipse is considered total. However, solar eclipses more tightly restrict where you can see them because the Moon casts a smaller shadow than Earth does. (But there's still an element of luck involved - after all, the sky has to be clear!) A sharp-eyed observer will notice that one side of the full Moon's disk looks a little dusky.įortunately, every lunar eclipse is observable anywhere on Earth where the Moon is above the horizon. If the Moon skims part way into the umbra, as shown at right, only the partial phases occur - you'll see part of the Moon in nearly full sunlight, and part of it steeped in the deep, red-tinged umbral shadow.Īnd if its disk passes just outside the umbra, it still encounters the weak penumbral shadow cast by Earth. ![]() That was the case during the widely viewed event in September 2015, which marked the conclusion of a series of four consecutive total lunar eclipses in 2014–15! Such eclipse tetrads are not common - the last one occurred during 2003–04, but the next won't begin until 2032. If it goes all the way in, we see a total lunar eclipse that's preceded and followed by partial phases. A long-exposure image captured red hues on the portion of the Moon inside the umbra during the lunar eclipse on October 8, 2014. Three types of lunar eclipse are possible ( total, partial, and penumbral) depending on how deeply the full Moon plunges into or near the umbra, our planet's dark, central shadow. In 2019, for example, two eclipses occur in January, two in July, and one in late December. ![]() (The technical name for that, by the way, is syzygy.) And, as the diagram above implies, those alignments occur roughly six months apart. These alignments don't happen at every new and full Moon because the lunar orbit is tipped about 5° to Earth's orbital plane - only occasionally do the Sun, Earth, and Moon line up exactly enough for an eclipse to occur. Jay AndersonĪ solar eclipse, such as the one in August 2017, occurs only at new Moon, when the lunar disk passes directly between us and the Sun and the Moon's shadow falls somewhere on Earth's surface.Ĭonversely, a lunar eclipse takes place during full Moon, when our satellite passes through Earth's shadow. Eclipse "windows" occur six months apart. Why Do Eclipses Happen? Eclipses of the Sun or Moon can only occur when the Moon crosses the plane of Earth's orbit (orange circle) very close to the time of new or full Moon. The mix of five events occurring in 2019 is especially interesting, because no two will be alike! There'll be three different types of solar eclipse - one each of partial, annular, and total - along with a total and a partial lunar eclipse. Up to seven eclipses of the Sun and Moon can take place in one year, though the last time that happened was 1982, and the fewest possible is four. There'll be something for everybody in 2019, with total, annular, and partial solar eclipses - and total and partial lunar eclipses to look forward to.
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