Baffling discovery at galaxy’s heart
SPACE is full of surprises.
This is another one.
Astronomers caught the first glimpse of strange stringlike structures at the heart of our galaxy back in 2012.
They show up on radio telescopes so far. Which is why they're called nonthermal radio filaments (NRF).
We can't actually see them in the visual spectrum. There are simply too many stars and too much dust and gas between us and the Milky Way's centre.
We must rely on wavelengths that can pass through this interference.
Now the Harvard-Smithsonian Center for Astrophysics in Cambridge has found one winding its way towards Sagittarius A - the supermassive black hole at the very core of our galaxy.
The results have been published in the science journal Astrophysical Journal Letters.
It appears to reach all the way to its immense event horizon - where not even light can escape its immense gravitational pull.
So what is it?
Is it a stream of super-excited particles being spun out of the black hole and into deep space?
Or is it a split in the fabric of space-time itself?
STARING INTO THE ABYSS
There aren't many radio telescopes operating at the wavelengths necessary to peer into the heart of our galaxy - yet.
But those that are will shortly give us our first direct 'view' of a black hole.
Earlier this year, radio telescopes around the world all focused on Sagittarius A at the same time to capture a picture of the greatest possible detail. It's been undergoing filtering and analysis ever since - and is due to be released early next year.
But this separate view of our galactic heart picked up a glowing vein.
"With our improved image, we can now follow this filament much closer to the galaxy's central black hole, and it is now close enough to indicate to us that it must originate there," says Mark Morris of the University of California, Los Angeles, who led the study. "However, we still have more work to do to find out what the true nature of this filament is."
UNTANGLING THE CLUES
So what could possibly cause long, thin filaments of excited particles to glow in the radio spectrum?
One idea is that these streams may be a by-product of our galaxy's magnetic fields blending in such a way as to create natural particle accelerators - similar to those scientists are using now in an effort to find the smallest building blocks of our universe.
The rotating black hole could be interacting with gas clouds around it to create a towering magnetic field reaching out from its event horizon. This could result in particles being accelerated as they are blasted outwards - producing radio waves.
Another, more radical, idea is that these lines may actually be 'cracks in space' (called a topological defect) - split from the vacuum of space as it expands. While still purely in the realms of theory, these could potentially carry mass and electric currents in a form similar to these observed filaments. Theorists have predicted that if they were to be found, they'd be found close to the centre of galaxies.
ON THE CUSP OF DISCOVERY
"Part of the thrill of science is stumbling across a mystery that is not easy to solve," says astronomer Jun-Hui Zhao from the Harvard-Smithsonian Centre.
"While we don't have the answer yet, the path to finding it is fascinating. This result is motivating astronomers to build next generation radio telescopes with cutting edge technology."
Astronomers around the world now want answers.
"We will keep hunting until we have a solid explanation for this object," says Miller Goss from the National Radio Astronomy Observatory. "And we are aiming to next produce even better, more revealing images."