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Astro-QA #3 : How many moons in our solar system can cause total solar eclipse?

According a study based on 141 moons, whose  orbits are known, it is found that around 32 moons can hide the Sun’s disk completely as seen from their planet’s surface. 

Many of these are extreme.  Pluto’s Charon, which looms 200 times larger than the Sun in Pluto’s sky. Next is Neptune’s Triton, 27 times larger than the Sun in Neptune’s sky. Other whopping-big moons include Neptune’s Despina, 17 times larger and Uranus’s Ariel  15 times larger. Jupiter’s Galilean moon Callisto can appear just 1.3 times larger than the Sun when low in the Jovian sky.

The only moons that seem to be capable of a near-perfect fit like our moon are Saturn’s Epimetheus, Prometheus, and Pandora. Each has an irregular shape, so a total eclipse by one of them is not likely to show the Sun’s corona in all its glory, nor the beautiful array of prominences and Baily’s Beads that we often behold from Earth.

Many other moons in the solar system would always appear smaller than the Sun’s disk. Although the size of Neptune’s Nereid is still poorly known, when near the low point of its highly elongated orbit it might cover up to 80 percent of the Sun’s diameter. And Mars’s Phobos is wide enough to span 69 percent of the Sun’s diameter when Mars is at aphelion — but for less than 10 seconds as this tiny moon glides by!

Yes, we are very lucky.

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