A long time ago, in a galaxy far, far away… at about 2 billion light years away from Earth lies radio-galaxy Hercules A, also known as 3C 348. At a first glance it looks just like another massive galaxy out there – at least when looking in the visible spectrum. In the radio wavelengths however, the story is completely different. The galaxy has been known for a long time among the brightest extragalactic radio source in the entire sky.
Astronomers using the recently upgraded Karl G. Jansky Very Large Array (VLA) radio telescope in New Mexico, revealed huge jets of material – 1.5 million light-years wide – that literally dwarf the galaxy that emits them (for comparison, our own galaxy is just 0.1 million light years wide).
The jets consist of very-high-energy plasma beams, subatomic particles, all interacting with strong magnetic fields are streaming out at nearly the speed of light from the galaxy’s central super-massive black hole which, by comparison, is 1000 times more massive then our Milky Way’s central singularity. At such speeds, the plasma streams become subject to relativistic effects that cause the innermost parts of the jets to be invisible, not even in the radio spectrum, the photons being directed away from our viewpoint.
As the plasma is progressively slowed down by interacting with a very hot, X-ray-emitting cloud of gas that surrounds this galaxy, the two lobes that can be seen in this image, become visible in the radio spectrum. The X-Ray emitting cloud of gas is not shown here, in this optical-radio composite. The ring-like structures visible in the outer portions of the jets point towards a less uniform nature of the plasma stream coming from the super-massive black hole, that perhaps sometimes, comes in bursts.
“The side that has the dust bubbles is the side with the normal looking collimated jet and the side with what looks like more entrained dust is the side that has the very unusual bubbles in the radio,” she said. “We’re perplexed so far.”
“One side has dusty filaments of cold gas that lie along the edges of the radio jet, suggesting they have been dragged along, or entrained, by the out-flowing radio plasma; but the other side of the source shows dusty filaments which resemble two bubbles,” said astronomer Stefi Baum, of the Rochester Institute of Technology (RIT).
[Story via Nasa News]