03/23/2021 – Ephemeris – The Moon tonight: Bay of Rainbows

This is Bob Moler with Ephemeris for Tuesday, March 23rd. Today the Sun will be up for 12 hours and 19 minutes, setting at 7:59, and it will rise tomorrow at 7:37. The Moon, 2 days past first quarter, will set at 5:50 tomorrow morning.

A look at the Moon tonight will reveal that the sunrise line, or terminator has almost completely revealed the large Sea of Showers or Mare Imbrium to the upper left of the center of the gibbous disk. At the extreme upper left nearly completely in sunlight a very popular feature, the Bay of Rainbows or Sinus Iridium. It’s a colorful name for something that’s as gray as the rest of the Moon. It looks like a bay off of Imbrium, and has an arch like a rainbow. Its arch is the Jura Mountains, which jut into Mare Imbrium at Cape Heraclide, just catching sunlight, and Cape Laplace farther into morning. What’s cool is catching it as the sunlight is hitting the mountains while the convex floor, following the Moon’s curvature is only partially illuminated.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Moon a little before how it will appear tonight highlighting Sinus Iridium. By tonight the floor of Sinus Iridium should be pretty much sunlit, and the Jura mountains completely lit. Created using Virtual Moon Atlas.

Sinus Iridium at sunrise. Photo by “Seb2003” on http://forums.futura-sciences.com/materiel-astronomique-photos-damateurs/5809-images-de-lune.html.