Blazars –The Most Impressive Astrophysical Events in Existence?


While examining distant extra-galactic sources, a team of astronomers at the University of Geneva’s Center for Astrophysics found something startling; distant sources such as blazars and highly energetic galactic nuclei seemed sapped of their predicted strength. This effect is the same without variation in all directions, which suggest that free floating magnetic fields range the cosmos, perhaps predating the modern day galactic fields.

These intervening fields are a predicted cause of the observed drop in gamma-ray energy from these distant sources. Could the universe itself have an overall polarized field? Or is there another effect that has yet to be accounted for, such as intervening dark matter or dark energy?  Further analysis by Fermi and other scopes soon to come online may prove to be key to unraveling this mysterious effect.

Another international team of researchers have stared down the barrel of one of the most violently energetic objects in the universe – and they didn't blink.  Instead, they've figured out the physics behind one of the most impressive astrophysical events in existence (that we know about).

BL Lacertae is a blazar, a supermassive galactic-core black hole emitting vast and variable beams of energy.  Please understand that giving this thing a name like "blazar" is like calling a speeding sixteen wheeler truck full of professional wrestlers, grizzly bears and dynamite a "gentle prodder." The English language simply lacks the ability to get across the staggering scale of these events – because it doesn't have a case above upper or letters bigger than capital.

The most famous property of black holes is the event horizon, the "point of no return" beyond which you cannot escape.  But even before this final barrier you're still close to a gigantic gravitational well built out of most of an Active Galactic Nucleus (AGN) – if not a point of no return, it's still a "point of incredibly difficult to escape from".  We observe vast, super-energetic near-light speed particle streams from the poles of some such systems – what gives them the power?

That was the question Professor Alan Marscher and an international team set out to answer, confirming their theories with observations of the inner workings of the BL Lac blazar particle stream.  Big questions need big tools (especially when they're over nine hundred million miles away), so they enlisted the help of a global network of satellites including the Very Large Baseline Array (VLBA), a continental set of dishes with resolution equivalent to a dish larger than the USA.

These mega-scale observations tracked particles as they were hurled from the throat of the blazar, emitting radiation as they go, and confirmed the team's theories that the power source is massively compressed and twisted magnetic fields.

As material is sucked into the black hole, it spirals in along a large accretion disk.  As it gets closer to being consumed, the material is crushed smaller and smaller by increasing gravitational forces – and the magnetic field lines coming along with it are crushed together as well, creating hugely intense fields oriented around the spinning black hole.  These gigantic fields can drive particles away from the hole, causing them to corkscrew along a narrowly confined path while emitting precise bursts of radiation – bursts the astronomers observed exactly.

Understanding these universe-grade events is a great step forward in astrophysics – for one thing, The BL Lacertae blazar is a particle accelerator that makes the LHC look like boy's toy.

In the radio image at the top of the page, two jets shoot out of the center of active galaxy Cygnus A. GLAST -The Fermi Xray Space Telescope, may solve the mystery of how these jets are produced and what they are made of.  Active galactic nuclei will be GLAST's bread and butter.

"When GLAST detects a blazar, it is monitoring violent activity from a black hole taking place in the distant past," says GLAST Interdisciplinary Scientist Charles Dermer of the Naval Research Laboratory in Washington, D.C. "Understanding gamma rays from these sources is a form of black hole archeology that reveals the high-energy history of our Universe."

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