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SYFY WIRE Bad Astronomy

The Newest New Moon

By Phil Plait

The picture above is likely the newest new Moon youâll see: The crescent above is actually a record-breaker; the thinnest crescent Moon ever photographed!

It was taken by the astrophotographer Thierry Legault, who (as oxymoronic as it is) routinely takes extraordinary photos. He shot it from his backyard near Paris on Monday at 07:14 UTC, when the Moon was a mere 4.4 degrees from the Sun. For comparison, the Sun and Moon are about the same size in the sky, just 0.5 degrees in diameter.

The geometry of this is interesting. Back in 2010, Legault took a similar shot when the Moon was a wee bit farther from the Sun, and I explained it all then if you want details. But in a nutshell, the Moonâs orbit is tilted a bit with respect to Earthâs, so it doesnât pass directly in front of the Sun every orbit (which is why we donât get a solar eclipse every month). Depending on the geometry at new Moon, it slides near the Sun, though never getting more than about 5 degrees away.

Therefore, at one particular moment, in the sky the Moon will be as near the Sun as it can get for that particular month. It was at that moment that Legault took the picture above. He got the timing to within a minute of the actual moment of newest Moon, so only the thinnest slice of the lit lunar landscape was visible from Earth.

As a reference, here is how much of the Moon was lit at that time:

I got that from the U. S. Naval Observatory, and shows the current phase of the Moon. You can see that the vast majority of the Moon was dark, with only the narrowest sliver lit at the top. (I rotated the image to match the actual photo.) Legault had to use a computer-programmed telescope to find it at all.

Because the Moon was so faint and the Sun (and sky around it) so bright, he set up a piece of wood with a small circular hole in it to cut down on sky glare and used a near-infrared filter, where the sky is even fainter. Even so, this was an incredibly difficult shot to take, and he deserves kudos for it. For the record, Iâll note the Moon can get even closer to the Sun than this, making for an even more difficult picture. But if anyone is up to the task to snap that and break this current record, itâs Thierry!

Related Posts (featuring Legault's work):

ISS, Shuttle transit the Sun!
Check. This. Out. Amazing photo of the Sun...
Doomed Russian Mars probe seen from the ground
Moonbow, Milky Way, meteor
SERIOUSLY jaw-dropping pictures of Endeavour and the ISS!
Discovery spacewalk seen from the ground

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