Astronomy is all about cycles: sunrise, sunset, eclipses, orbits... and even the cycle of life, if we wish to be metaphorical. Stars are born, live out their lives, and then die. Some fade away, and others explode, leaving a lasting imprint on space around them for a long, long way.
This cycle is played out everywhere, including the weird trunk-like nebula called IC 5146, seen here in the far-infrared by Europe's space-based Herschel Observatory. The light you're seeing here has wavelengths hundreds of times what our eye can see, meaning it has hundredths the energy. This stuff is cold; mere degrees above absolute zero. What's glowing here is actually quite dark in visible light, with the exception of the glob on the left, which is where stars are being born - they light up the surrounding gas, making it visible to us.
But that long filament that stretches to the right? That is actually dust that's been riled up by exploding stars. When a supernova goes off, a shock wave of material blows away from it. That wave slams into waves from other stars that have exploded, and the gas gets all mixed up, like contrails from two passing jets. It's turbulent, and that tends to create long filaments like the one in IC 5146. They're all over the sky, a testament to the number and sheer power of supernovae. And that gas can compress, too, and form new stars... starting that cycle all over again.
Image credit: ESA/Herschel/SPIRE/PACS/D. Arzoumanian (CEA Saclay) for the “Gould Belt survey” Key Programme Consortium