LDN 933 – Dark Clouds in Cygnus
Key Scientific Data
Object type: Dark nebula – interstellar dust and molecular cloud
Constellation: Cygnus
Other designations: LDN 933, Lynds Dark Nebula 933
Catalogue: Lynds' Catalogue of Dark Nebulae (1962)
Associated region: Cygnus Rift
Nearby bright star: 57 Cygni
Nearby nebulae: LBN 359, IC 5070 (Pelican Nebula)
Composition: Cold molecular gas and interstellar dust
Notable features: Dense dust filaments, obscuring clouds and blue reflection nebulosity
Right Ascension: approximately 20h 52m
Declination: approximately +44° 11′
Location: Galactic disc of the Milky Way
Light-travel time: Not uniquely determined; the field contains objects at different distances
Description
LDN 933 is a remarkable dark nebula located in the constellation Cygnus, within the extensive interstellar cloud system known as the Cygnus Rift.
Unlike emission nebulae, LDN 933 is visible primarily because its dense concentrations of dust and molecular gas obscure the stars and luminous material behind them.
This image reveals an intricate network of dark filaments against the rich stellar background of the Milky Way, alongside delicate bluish nebulosity surrounding the bright star 57 Cygni.
The Cygnus Rift
LDN 933 belongs to the vast system of interstellar clouds responsible for the dark band that appears to divide the Milky Way during northern summer nights.
This apparent gap is not an absence of stars but the result of interstellar extinction, as foreground dust absorbs and scatters light from more distant stellar populations.
The varying transparency of the clouds reveals differences in their density and distribution, creating the distinctive appearance of dark rivers flowing through the Galactic star field.
57 Cygni and Reflection Nebulosity
One of the most striking features of this photograph is 57 Cygni, the bright star on the right, surrounded by faint bluish nebulosity.
Unlike the reddish glow of ionised hydrogen, this light is produced by interstellar dust scattering starlight, with shorter blue wavelengths generally scattered more efficiently.
The same physical principle contributes to the blue colour of Earth's daytime sky.
The field also includes LBN 359, part of the complex mixture of dust and nebulosity found near the North America–Pelican region.
Dark Clouds and Star Formation
Despite their dark appearance, molecular clouds contain enormous quantities of gas and dust, the fundamental ingredients of future stars.
Within sufficiently cold and dense regions, gravity can initiate the collapse of molecular material, eventually forming protostars and potentially planetary systems.
Infrared observations can penetrate much of the obscuring dust, revealing objects hidden from visible-light telescopes.
Dark nebulae are therefore not empty spaces but important components of the stellar life cycle.
Curiosities
LDN 933 was catalogued in 1962 by American astronomer Beverly T. Lynds, whose survey identified thousands of dark nebulae across the sky.
Its designation belongs to the Lynds Catalogue of Dark Nebulae, which helped establish these obscuring clouds as distinct astronomical objects.
An unusual characteristic of dark-nebula photography is that the darkest regions can contain the greatest concentrations of matter.
Astronomers can investigate these clouds by measuring how much they dim and redden background stars, providing information about the distribution of interstellar dust.
Looking Back in Time
Unlike a distant galaxy or a single star cluster, LDN 933 does not have one precisely defined light-travel time.
The photograph contains several layers of the Milky Way, with foreground dust obscuring stars located at different distances.
Some of the visible starlight may have travelled for hundreds of years, while other photons began their journey thousands of years ago, when ancient civilisations were developing on Earth.
During their passage towards us, some photons were absorbed or scattered by the intervening clouds, creating the dark silhouettes recorded in this image.
The photograph therefore captures different moments in the history of our Galaxy, revealing both the light that reached Earth and the interstellar material that intercepted it.
Image Data
Total integration time: 11h 28m
Integration by filter:
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L-Pro: 5h 52m
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Red: 1h 45m (35 × 180")
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Green: 1h 51m (37 × 180")
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Blue: 2h (40 × 180")
Equipment:
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Telescope: Artesky ARTEC 250 Pro
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Camera: ToupTek ATR2600M
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Mount: 10Micron GM2000 HPS II
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Filters: Optolong Blue 2", Optolong Green 2", Optolong L-Pro 2", Optolong Red 2"
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Accessories: Pegasus Astro Prodigy Microfocuser, ToupTek AFW-L 7×2", WandererAstro WandererBox Pro V3
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Software: Adobe Photoshop, Pleiades Astrophoto PixInsight, Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA)
For further details and the full-resolution image, visit AstroBin: