MadSci Network: Astronomy

Re: What causes the haze around the moon?

Date: Mon Apr 19 17:12:20 2004
Posted By: Vladimir Escalante-Ramírez, Faculty, Institute of Astronomy, National University of Mexico
Area of science: Astronomy
ID: 1081186470.As

When the light from the Sun or the Moon shines through the atmosphere, it 
illuminates particles suspended in the air and produces a number 
of different phenomena depending on the kind of particles that 
are more abundant at that moment. Some of the more common 
are the haze and halos around the Moon and Sun, which are produced 
by ice crystals in the upper atmosphere, often associated with 
cirrus clouds. It is not well understood how these crystals 
form, but the fact that the halo forms at 22.5 degrees from the 
Moon or the Sun means that it is caused by them. 
There is a nice picture and some more explanations in

Perhaps the most common cause of haze is produced by water droplets 
in humid weather. Other kinds of particles like dust, soot or 
volcanic ash can produce different phenomena when the light from the 
Sun or the Moon shines through them. You can read an interesting 
account of them in

Even Venus can produce atmospheric phenomena like the Venus pillars,
which are vertical rays, which are produced by light being reflected 
from suspended ice crystals close to the ground. It is of course more 
common to see Sun or Moon pillars. For a more complete and beautiful 
account of atmospheric optics see

Vladimir Escalante Ramírez

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