dipper@utastro.UUCP (Debbie Byrd) (02/12/86)
Earthshine is that soft glow on the dark part of a crescent moon. We'll talk more about it -- after this. February 12 Earthshine On clear nights, when the moon is nearly full, you'll often see the landscape bathed in white moonlight. If you lived on the moon, you'd see a similar soft light flooding the stark lunar landscape, whenever a "full Earth" was in your sky. Earthlight can illuminate the night side of the moon -- just like moonlight shines on Earth. In fact, you don't have to live on the moon to see earthlight shining there. You can see it from Earth on evenings that the moon is a slender crescent, located in the western sky. On such evenings, the moon is just past its new phase, when it's between the Earth and sun. What you'll see is light from Earth, reflected onto the darkened portion of the moon. We call this reflected light "earthshine." Leonardo da Vinci was the first to identify it as being the same type of phenomenon as moonlight shining on Earth. If you want to have a look at earthshine, find the moon in the west in early evening, when it's a few days past new. The crescent will be slim and bright, and the darkened portion of the moon will glow dimly. At its best, earthshine can illuminate the dark part of the moon so much that some large lunar features show up in binoculars. The crescent, meanwhile, looks larger than the moon's dark side -- just because it's brighter. Take a look. The moon was new several days ago. And it's in the west each evening this week. You can see earthshine -- maybe tonight! Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin