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We know that the Moon doesn't have an atmosphere; thus the sky is seen dark.

Also, from this question, the angular diameter of the Earth viewed from the Moon is a bit bigger than $2^\omicron$ at the perigee, meaning that it will block the Sun completely (the Sun has an angular diameter of $0.538^\omicron$).

If a total lunar eclipse occurs at the perigee can the astronauts on the Moon see the Earth? Or do they just see it like other dark parts of the sky?

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  • $\begingroup$ I don't think it matters whether it's a total lunar eclipse. If a person is in the umbra of the Earth, I don't think what they see will be affected by whether the rest of the moon is eclipsed. $\endgroup$ Mar 21 at 22:49

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The Sun eclipsed by the Earth was actually recorded in 2009 by the Japanese lunar satellite Kaguya (athough this was strictly speaking not a total eclipse as such; see explanations below)

enter image description here

Here the report (from which the photo sequence was taken)

https://global.jaxa.jp/press/2009/02/20090218_kaguya_e.html

Here the corresponding video in (near) real time

The fact that the ring gets bigger from the top is due to the circumstance that the event happened exactly at Earth rise, so the bottom part is blocked off by the Moon's surface.

To avoid any misunderstandings of what can be seen here: as mentioned in the linked referencem this was a penumbral lunar eclipse, i.e. the Sun was only partially eclipsed by the Earth as seen from the Moon. So the diamond ring effect is here not the end of a total eclipse (as we are used to from solar eclipses as seen from Earth), but it is due to the uneclipsed part of the sun just rising over the lunar horizon. In the earlier part of the video it was still blocked by the Moon's surface. Due to the fact that the Moon has no atmosphere this looks then pretty much like a total eclipse up to this point

A true total eclipse of the Sun by Earth was however recorded in 1969 by the Apollo 12 astronauts on their way back home from the Moon. See this video, taken with an (apparently hand-held) 16mm movie camera

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    $\begingroup$ Did the eclipse end at 0:40? $\endgroup$ Mar 19 at 18:28
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    $\begingroup$ @SnackExchange Yes, the eclipse ended at 0:40. The Sun appears again from behind the Earth $\endgroup$
    – Thomas
    Mar 19 at 18:35
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    $\begingroup$ That's... so.... beautiful! $\endgroup$
    – uhoh
    Mar 19 at 21:17
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    $\begingroup$ @SnackExchange Don't forget that this footage is from a moving camera. Kaguya had an orbital period of just under 2 hours (7109 seconds). $\endgroup$
    – PM 2Ring
    Mar 19 at 21:17
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    $\begingroup$ @SnackExchange I have to correct myselff. The occurance of the Sun at 0:40 was actually not the end of the Earth/Sun eclipse but the begiining of sunrise. After all, this was a penumbral lunar eclipse (as mentioned in the reference) , that is the Sun was only partially eclipsed by the Earth as seen from the Moon. It is only that in the first part of the video the Sun was still blocked by the Moon's surface. $\endgroup$
    – Thomas
    Mar 19 at 21:48
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Can the Earth be seen from the moon when we have a total lunar eclipse at the perigee?

Yes - but primarily it's the Earth's atmosphere that you would see.

Earth's atmosphere will refract and scatter light around its edge.

This is not a surprise, we can see that the Moon gets very dark red and brown, but not quite black. That of course means light is getting past Earth.

While the whole moon can be inside the geometrical umbra the further from the umbra's center the brighter the Moon, so the brighter the light coming through Earth's atmosphere, since it requires less refraction and scattering to get there.

This gets even weirder than what you imagine, the Hubble space telescope looked at diffuse light reflected from the dark Moon during a lunar eclipse in order to collect light that refracted and scattered through Earth's atmosphere around its edge.

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    $\begingroup$ Is your answer yes because a lunar astronaut would see a ring of atmosphere lit by refracted light? $\endgroup$
    – JohnHoltz
    Mar 19 at 17:08
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    $\begingroup$ @JohnHoltz I've added a "Yes", thanks! $\endgroup$
    – uhoh
    Mar 19 at 21:16
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The Moon as seen from the Earth looks dark red during a total lunar eclipse — it doesn’t go completely black and disappear. That’s because it is still partly illuminated by sunlight refracted through the Earth’s atmosphere, and of course light that’s bright enough that we can see its reflection from Earth would be very conspicuous when seen directly from the Moon.

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