Can one observe an annular eclipse of the moon?

Why or why not?

Thank you in advance! It's for my Astronomy homework.

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  • 9 years ago
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    Well, ..., There is no such thing as an annular lunar eclipse.

    There is, however, a pen-umbral lunar eclipse where the moon misses Earths umbra and glides through the pen-umbra. Maybe this is what you're thinking of In these cases, the full moon itself will marginally dim. Believe me, I've sat through one before and the dimming of the moon is barley precipitable. You will not see a dark shadow call on the face of the moon.

    Then there is the partial lunar eclipse where part of the moon enters Earth's umbra. This would be a partial lunar eclipse and part of the earth's shadow would fall on the moon creating a dark area on the moon.

    Some people mistakenly think that an antumbral eclipse is possible (one where the moon is too far away to be covered by the earth's umbra. However this is an impossibility as the moon's semi-major axis is much shorter than the Earth's umbra.

    So, no, there is no annular eclipse of the moon and nothing that even looks like it.

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  • No, you can only see annular eclipses of the sun. We see an eclipse when the sun, earth and moon are all in a straight line. If the moon is between the sun and the earth, it's a solar eclipse. When the earth is between the moon and the sun, you get a lunar eclipse.

    By a fluke of nature, the sun and the moon appear almost exactly the same size in our sky, so that the moon just covers the sun's disk during a solar eclipse. If the moon is at apoapsis (the farthest from the earth in it's orbit), it's a little too small to completely cover the sun, and so you get an annular eclipse, where you see the moon outlined by a ring of the sun's visible disk.

    The earth appears much larger in the lunar sky than the moon does in our sky. When there is a total lunar eclipse, the earth is always big enough to blot out the entire sun

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  • 9 years ago

    The earth's shadow on the moon is much larger than the moon's shadow on earth. Or, put another way, when you look at the sun and moon from earth, they appear to be about the same size, but when you look at the sun and the earth from the moon, the earth appears much larger. In fact, the earth is so large in this comparison, that the shadow of the earth at the orbit of the moon is larger than the moon itself! (Whereas the shadow of the moon at the orbit of the earth just barely touches the earth.)

    This means there is no way for a bit of sun to appear around the entire edge of the earth's shadow when viewed from the moon *or* from the earth, so an annular eclipse of the moon is impossible.

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  • 9 years ago

    By "eclipse of the moon"...I assume you specifically mean a lunar eclipse where the moon passes behind the Earth.

    The reason why one cannot observe an annular lunar eclipse is that the moon never passes in the antumbra of the Earth's shadow-field.

    Here is a scale model of the moon in Earth's umbral shadow. Notice how its sides are badically parallel lines? The moon never passes in the antumbra of Earth.

    The antumbra of Earth doesn't begin until well-past the orbit of Mars. Maybe if very lucky to live at the right time...an observer could observe a very unprobable Martian eclipse of Mars in the Earth's shadow during Mars opposition.

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  • ?
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    9 years ago

    Yes, one can.

    The reason is, that the Moons orbit is not perfectly circular, but elliptical. The distance to the moon from the earth actually changes as much as 40,000 miles per orbit. This causes the moon to occasionally not quite cover up the sun when it passes between the two bodies. This therefore gives rise to the annular eclipse.

    EDIT: Oh, of the moon? umm, maybe not.

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