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The Tulip Nebula

Explanation: Framing a bright emission region this telescopic view looks out along the plane of our Milky Way Galaxy toward the nebula rich constellation Cygnus the Swan. Popularly called the Tulip Nebula the glowing cloud of interstellar gas and dust is also found in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101. About 8,000 light-years distant and 70 light-years across the complex and beautiful nebula blossoms at the center of this composite image. Red, green, and blue hues map emission from ionized sulfur, hydrogen, and oxygen atoms. Ultraviolet radiation from young, energetic stars at the edge of the Cygnus OB3 association, including O star HDE 227018, ionizes the atoms and powers the emission from the Tulip Nebula. HDE 227018 is the bright star very near the blue arc at the cosmic tulip's center. Glowing across the electromagnetic spectrum, microquasar Cygnus X-1 and a curved shock front created by its powerful jets lie toward the top and right.

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Below HD 227018, the ionizing star of the Tulip Nebula, is a little reddish dot and then a whitish, brighter star. The whitish star is actually a red giant whose parallax is very similar to that of HD 227018, although its proper motion is different by being slower. Closer to the center of the image, inside the left part of the orange arc of the Tulip Nebula, is another whitish-looking star. That, too, is a red giant with the same parallax as, but slower proper motion than, O-type star HD 227017. It is as if these stars all belong together, but the O-type star is hot and blue, and compared with the others, it is speeding.

The star HD 226868, the star orbiting the invisible black hole of Cygnus X-1, also has a very similar parallax to the other stars, and its proper motion is somewhere between the O-type star and the red giants. This is certainly a fascinating part of the sky.

What I find most fascinating about the image itself is seeing the arc created by Cygnus X-1. But I also like seeing its relationship with the stars of the Tulip Nebula.

Ann

Can someone answer a question for me? I know that nearly all of the gas out there is hydrogen, but in this picture the hydrogen is colored green and the sulfur is colored red, and the picture appears to have a lot more reds than greens (or yellows). So anyway, why does the glowing sulfur seem so much more apparent than the glowing hydrogen?

Rules For wrote:Can someone answer a question for me? I know that nearly all of the gas out there is hydrogen, but in this picture the hydrogen is colored green and the sulfur is colored red, and the picture appears to have a lot more reds than greens (or yellows). So anyway, why does the glowing sulfur seem so much more apparent than the glowing hydrogen?

It isn't apparent to me that the sulfur is dominant. I'd say that the major color we see is in the yellow range, which means approximately equal contributions from red (sulfur) and green (hydrogen). Then, there's the processing, where it's common to stretch out each channel to fill the available display dynamic range. Finally, keep in mind that while most of the gas is hydrogen, all we're seeing here is gases in their ionized form, which may have little to do with their broader concentrations.

I'm surprised that not much information is available about the bowshock near the centre of the nebula. Is the associated star a runaway star? I wonder what the Spitzer view of this area looks like.

Also you can see the nebula associated with Cygnus X-1 in this image by Don Goldman.

I think the first image was this one: http://apod.nasa.gov/apod/ap090608.html

In the images brought up through the "this telescopic view" link there is one labelled 'A microquasar Cygnus X-1 Shown in a starless image' that better shows that area for anyone not quite sure where Cygnus X-1 is in the main (and excellent) image.