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Saint Patrick's Day is associated with the shamrock and the color green. Although there don't seem to be any cosmic shamrocks, there are many green phenomena in the skies. Discover a beautiful green nebula, what excites electrons, and why con men sold “comet pills”.

Saint Patrick's Day – Wearing the Cosmic Green

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Alien visitors on St. Patrick's day!
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Hanny's Voorwerp (Dutch for Hanny's object) is a rare type of astronomical object called a quasar ionization echo. It was discovered in 2007 by Dutch schoolteacher Hanny van Arkel while she was participating as a volunteer in the Galaxy Zoo project, part of the Zooniverse group of citizen science websites. Photographically, it appears as a bright blob close to spiral galaxy IC 2497 in the constellation Leo Minor.

The voorwerp is green. In fact, imaged by the Hubble Space Telescope, it looks like a frog.
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It looks like a frog.

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Ireland doesn't get much by the way of northern lights. You have to be significantly farther north to see the sky green like this: In the Embrance of a Green Lady

The photo was taken by Filip Hrebenda and was the winning Aurora photo in the 2022 Astronomy Photographer of the Year competition.

St Patrick had no comment, but Sheila Kanani, one of the competition judges, said: "I love this photo because it really sums up aurorae for me: the green ‘swoosh’ reflected in the icy lake, the clarity of the edges of the ice blocks and the looming shadow of the mountain. Fantastic!"