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The Tulip Nebula (Sh2-101) and Cygnus X-1 Bow Shock

Technical card

Resolution: 3267x2379

Dates:July 12, 2019July 24, 2019Aug. 4, 2019

Astrodon Narrowband 3nm Ha: 28x1200" -20C bin 1x1
Astrodon Narrowband 3nm OIII: 41x1200" -20C bin 1x1
Astrodon Narrowband 3nm SII: 30x1200" bin 1x1

Integration: 33.0 hours

Darks: ~50

Flats: ~20

Bias: ~100

Avg. Moon age: 12.02 days

Avg. Moon phase: 50.88%

Bortle Dark-Sky Scale: 5.00 job: 2865490

RA center: 299.724 degrees

DEC center: 35.404 degrees

Pixel scale: 0.974 arcsec/pixel

Orientation: 359.417 degrees

Field radius: 0.547 degrees

Locations: Home Observatory, Schenectady, New York, United States

Data source: Backyard


The Tulip Nebula (Sh2-101) is a HII emission nebula located in the constellation Cygnus at a distance of about 6,000 light years from Earth. It is in close proximity to microquasar Cygnus X-1, site of one of the first suspected black holes. Cygnus X-1 is the brighter of the two stars at the end of the lower petal of the Tulip.

Cygnus X-1 was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth. It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 14.8 times the mass of the Sun and has been shown to be too small to be any known kind of normal star, or other likely object besides a black hole.

Cygnus X-1 belongs to a high-mass X-ray binary system that includes a blue supergiant variable star designated HDE 226868[18] which it orbits at about 0.2 AU. A stellar wind from the star provides material for an accretion disk around the X-ray source. Matter in the inner disk is heated to millions of degrees, generating the observed X-rays. A pair of jets radiating from the accretion disk of the black hole are colliding with the interstellar material to form the curved shock front (in blue) at the right of the Tulip.




Luca Marinelli



Opened dark shadows lightly to optimize display on narrower-gamut monitors.


Added RGB star color.

Sky plot

Sky plot


The Tulip Nebula (Sh2-101) and Cygnus X-1 Bow Shock, 


            Luca Marinelli