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Very Young Moon

13 Jan 2014, 07:01 UTC
Very Young Moon
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Question: Last night after sunset I saw this really thin curved sliver of light in the west. At first I thought it was a UFO. Then I wondered if maybe it was just a very thin moon, because it was about the right size and shape. But I’ve never seen one that thin. Just how thin can the Moon get? — LB, Salt Lake City, Utah
Answer: No, it was an IFO (Identified Flying Object). I’m pretty sure what you saw was a very young Crescent Moon. When I entered the date from your email, and your location, my astronomy app recreated what you saw. It probably looked much like the photo above, which I captured earlier this year. That’s a very young Moon … my astronomy app tells me about 22.5 hours old. For comparison, this image, shot in 2012, shows a Moon about 3 days old.
When the Moon reaches its “New” phase it has essentially zero thickness. You can’t see it without special equipment (see Legault’s link below). From there it begins to wax (become increasingly more illuminated). You can see the entire lunar phase cycle in this NASA time-lapse from my 12 Nov 2012 post. Of ...

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