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Sharpless Sh2-33 - Integrated Flux Nebula in the constellation of Serpent

Short description:

Our image shows Sharpless Sh2-33, a large molecular cloud that belongs to the type of "integrated flux nebulae" (galactic cirrus). These are reflection nebulae that, unlike individual stars or clusters, are illuminated by the integrated energy flow of ALL the stars in our galaxy. They are concentrated in the direction of the northern and southern celestial poles and are therefore located far above the disk plane of our Galaxy.

The classification as Integrated Flux Nebulae (IFN) goes back to the American amateur astronomer Steve Mandel. These molecular clouds are extremely faint and Sh2-33 is a rather rarely recorded example of this type of nebula. IFNs have been little studied so far because they do not stand out against the image noise of the sky background in an imperfect dark sky.
Another example of such a molecular cloud in the constellation Apus of us can be seen here.

Stewart Sharpless (1926 - 2013) was an American astronomer at the U.S. Naval Observatory who published a catalogue of 313 H-II regions north of -27 degrees declination in 1959. However, some of the objects listed by Sharpless are not H-II nebulae but molecular clouds that reflect the light of all the stars in the Milky Way. They are the so-called Integrated Flux Nebulae, which Steve Mandel has catalogued in his Unexplored Nebulae Project. Read more here.

Much information about Steward Sharpless and his catalogue can be found on the website of the American amateur astronomer Dean Salman.

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