NASA Satellite Spots a Mysterious Green Space Blob That's Gone in a Flash

Pops of bright blue and green in this image of the Fireworks galaxy (NGC 6946) show the locations of extremely bright sources of X-ray light captured by NASA's NuSTAR space observatory. Generated by some of the most energetic processes in the universe, these X-ray sources are rare compared to the many visible light sources in the background image. A new study, published in the Astrophysical Journal, offers some possible explanations for the surprise appearance of the green source near the center of the galaxy, which came into view and disappeared in a matter of weeks.