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Paul Kohlmiller

This image is an artist’s conception of a blazar. These are typically found at the core of galaxies. They emit light throughout the EMR spectrum but very heavy in gamma-rays. The energy from the gamma-rays accelerates particles to near light speed and these accelerated particles emit infrared radiation. Image credit: NASA/JPL-Caltech


It has happened before in astronomy and it appears that it has happened again. Two distinct phenomena will originally suggest completely distinct origins but they both later are found to be the same thing, just seen in a different way. In this case we are talking about magnetars, rapidly spinning neutron stars with strong magnetic fields. They appear to be bright in X-rays and dark in radiowaves. Thus they were thought to be quite different from radio bright pulsars, neutron stars with high rotation rates but weak magnetic fields. But more recently a few magnetars have been seen to have pulses of radiowave emissions. The radio energy emitted is similar between the two types of stars. The different types of radio energy might be related to the rotational speed and the amount of x-ray luminosity.

So when has this kind of thing happened before? One great example is with quasars, and blazars. These are all very different manifestations of active galactic nuclei. If the energetic jets emitted by these AGN is coming right at us, we call it a blazar. If the torus of material around the AGN block visible light but lets us “see” the radio waves, we call it a quasar - a quasi-stellar radio source. Other AGNs are Seyfert galaxies, distant galaxies that emit low-energy gamma rays, lower than quasars. Blazars are actually less luminous than quasars because we see the jet of energy coming from the AGN and not the AGN itself.

New information indicates that blazars may be much more numerous than previously thought. NASA’s Wide-field Infrared Survey Explorer has found 200 blazars and more discoveries are likely. “Blazars are extremely rare because it’s not too often that a supermassive black hole’s jet happens to point toward Earth” said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto. “We came up with a crazy idea to use WISE’s infrared observations, which are typically associated with lower-energy phenomena, to spot high-energy blazars, and it worked better than we hoped.” This research should yield insights into the evolution of super massive black holes. NASA’s Fermi mission has identified hundreds of gamma ray sources and many are suspected blazars. WISE data so far indicates that just over half of the gamma ray sources are indeed blazars. “WISE’s infrared vision is actually helping us understand what’s happening in the gamma-ray sky” according to Raffaele D’Abrusco, a co-author of the papers describing the blazar detections.


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