Black holes are often thought to be a fairly destructive force in the universe -- but there's a lot more to them than meets the eye. Most galaxies, it seems, can't exist without them; and they also may play a role in the formation of stars and galaxies.
A new discovery by a team of researchers using the National Science Foundation's Very Large Array in New Mexico deals very much with the destructive side. Peering 1.1 billion light-years from Earth at an otherwise "boring" area of space called the Teacup Galaxy (J1430+1339) the team has discovered violent storm activity at its core -- demonstrating just how catastrophic black holes can be.
"It appears that a supermassive black hole is explosively heating and blasting around the gas in this galaxy and, as a result, is transforming it from an actively star-forming galaxy into one devoid of gas that can no longer form stars," said study lead author Chris Harrison from The Centre for Extragalactic Astronomy at Durham University in the UK.
The two most common types of galaxy that we have observed in the universe are spiral and elliptical. Spiral galaxies -- like our own Milky Way, and the nearby Andromeda -- make up around 60 percent of the galaxies we have seen, and are rich in gas and alive with activity and star formation. Ellipticals, on the other hand -- making up 10-15 percent of all galaxies -- have very little gas and very little star formation, ageing with a minimum of new growth.
These elliptical galaxies, researchers theorise, started out their lives as active star-forming galaxies -- after all, the stars had to come from somewhere -- yet at some point, star formation slowed almost to a halt. This, recent research suggests, could be due to the black holes in their hearts.
And perhaps those black holes are storming, if the Teacup Galaxy is any indication. It has been identified as having a supermassive black hole at its core actively consuming material and while it already has the appearance of an elliptical galaxy, observations have found gas surrounding the galaxy, indicating that it is only in the process of transitioning into an elliptical galaxy.
"For many years, we've seen direct evidence of this happening in galaxies that are extremely bright when viewed through radio telescopes. These, rare, radio-bright galaxies harbor powerful jets, launched at the black hole, that plow into the surrounding gas," Harrison said. "However, to understand how all of galaxies in our Universe formed, we needed to know if these same processes occur in less extreme galaxies that better represent the majority."
In the image captured by the VLA, two large "bubbles" of radio emission can be seen extending some 30,000 to 40,000 light-years on either side of the core, while smaller jets -- 2,000 light-years long -- drive into the gas, accelerating it to speeds of up to 1,000 kilometres per second (200,000 mph).
"These radio observations have revealed that the central black hole is whipping up a storm at the center of this galaxy, by launching powerful jets that are accelerating the gas in the host galaxy and are colliding with the gas on larger scales. This is the same kind of powerful process we'd previously seen in rare, extremely radio-luminous galaxies. The incredible capabilities of the VLA have allowed us to discover that these processes can occur in the more-common, radio-faint galaxies, as long as you look hard enough," said study co-author and fellow Durham astronomer Alasdair Thomson.
Since this discovery, the team has now observed eight more such objects displaying similar characteristics.
"This 'storm' in the 'Teacup' means that the jet-driven process in which a black hole is removing or destroying star-forming material may be much more typical than we knew before, and could be a crucial piece in the puzzle of understanding how the galaxies we see around us were formed," Harrison said.
The full paper has been published in the Astrophysical Journal, and can be viewed online via arXiv.