Something like 6000 light years away, roughly toward the downtown area of our galaxy, lies NGC 6604, a tight cluster of young, massive, hot, bright stars. Just starting to shrug off the gas cloud of its birth, these stars emit a fierce light that makes the gas glow. When you point the 2.2 meter ESO/MPG telescope at this cluster what you get is startling beauty:
[Click to ennebulenate, or grab the cosmic 8600 x 8400 pixel version.]
NGC 6604 is the compact group of bright blue stars in the upper left. This whole complex of gas (called Sharpless 2-54) is about 200 - 250 light years across, making it rather huge! You're only seeing a fraction of it here, though. It's actually part of an even larger series of nebulae which include the more famous Eagle nebula (the Pillars of Creation) and the Omega nebula.
The image is a composite of pictures from different filters. Ultraviolet and blue filtered images were combined to make blue in this image; green filtered light is colored green, yellowish light from nitrogen is yellow, and the red is actually red from warm hydrogen. As you can see, hydrogen is plentiful in this area!
Also, see those odd diagonal features on the lower left? Those extend for a long way, well outside the frame here. That structure is called a "chimney", and may be 650 light years long! As stars are born, they can blow massive winds from their surfaces. This puts pressure on the surround gas, and if there's a weak spot -- where the gas is less dense, or if it's near the edge of the cloud -- the winds can push through. It's not clear exactly how these form, or why they tend to be so straight. It's suspected magnetic fields are involved, but that complicates things hugely. Still, the chimney in Sharpless 2-54 is the closest one known (of dozens), providing a nice clear view of it. If we ever do figure out the detail mechanics of chimneys, no doubt this one will play a role.
Image credit: ESO
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