Misty Orion ~ Images from Hungary on the evening of 1st April '10 by Monika Landy-Gyebnar.
Images ©Monika Landy-Gyebnar.

Red giant Betelgeuse at top is surrounded by a diffraction aureole created by water droplets in our own troposphere. As is the blue supergiant Rigel at right and Orion's three belt stars Alnitak, Alnilam and Mintaka.

"Yesterday evening we went out photographing around some extinct volcanoes near Lake Balaton. A cold front was to come and we only had a little time before its clouds appeared at the western part of our sky. These clouds had not only faded the stars, but before it happened most of the stars developed a bright corona* around them.

It had an effect like a diffuse filter that made the stars look a bit fuzzy and also make their colours more easily observable. There was nothing special in it, only beauty of a natural phenomena helping us to record the real visible colours of the stars."

*Strictly speaking they are aureoles, coronas have rings. But Monika says "We in the Hungarian language do not have a different name for corona and aureole, both are called "koszorú' (literally a wreath - for the similarity of shape)."

Whether there is an aureole or a ringed corona depends on its brightness (sometimes the rings are just too faint to be visible) or the size distribution of the droplet scatterers. Droplets with a wide range of sizes do not produce coronae because any rings are also of different size and so overlap and are smeared away.

Note the size of the glows around the stars compared with that of the Bishop's ring in the previous OPOD. Both are aureoles but from droplets of vastly different dimension.

At left: Sirius, Homer's 'star that flames at harvest', has its aureole.


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