The spiral arms of our Milky Way galaxy are studded with clouds of gas and dust called nebulae. GL490 is one such nebula, and inside stars are busy being born.
In this image, a combination of Spitzer shots with those from the infrared survey 2MASS, what you see as green is light emitted from molecules called PAHs, or Polycyclic Aromatic Hydrocarbons... soot! These long-chain carbon molecules are opaque in visible light, but are warmed by the nearby stars to temperatures of about 100K. That's about -170 Celsius, or -280 Fahrenheit! So maybe "warm" isn't the best word, but to an infrared astronomer that's about right.
The hi-res version of this picture
reveals stunning details, including newborn stars shooting out long jets of gas (you can see one here just above and to the right of the yellowish star in the center). I'd also urge you to take a closer look at the yellow patch at top center; that is where dust is reflecting infrared light from a nearby star. The filaments, sheets, and tendrils in that area are simply stunning. Original blog postOriginal press release
Image credit: NASA/JPL-Caltech/2MASS/B. Whitney (SSI/University of Wisconsin)