Researchers have identified the first "bone" of the Milky Way — a long tendril of dust and gas that appears dark in this infrared image from the Spitzer Space Telescope. Running horizontally along this image, the "bone" is more than 300 light-years long but only 1 or 2 light-years wide. It contains about 100,000 Suns' worth of material. // Credit: NASA/JPL/SSC