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NASA’s WISE mission sees skies ablaze with blazars

The top image is an artist’s concept showing a “feeding,” or active, supermassive black hole with a jet streaming outward at nearly the speed of light. Such active black holes are often found at the hearts of elliptical galaxies. Not all black holes have jets, but when they do, the jets can be pointed in any direction. If a jet happens to shine at Earth, the object is called a blazar.

Blazars give off a full range of light, dominated by high-energy gamma rays. As particles in the jets are accelerated to almost the speed of light, they give off a specific infrared signature, which NASA’s Wide-field Infrared Survey Explorer (WISE) can detect. Astronomers have taken advantage of this fact, and used the WISE all-sky catalog to uncover more than 200 new blazars so far.

The second image, taken by WISE, shows one such blazar. Infrared light with shorter wavelengths is colored blue; and longer wavelengths are red. The blazar appears white compared to the other galaxies because it’s giving off infrared light at all four of the infrared bands used to make this image.

Some of the infrared radiation coming from the bazar is extremely peculiar. Galaxies often shine in infrared light due mainly to their cold dust; in this case, most of the observed radiation — called synchrotron — arises not from the host galaxy but from particles in the blazar’s jets accelerating to nearly the speed of light. »