AUSTRALIA.- Astronomers from the University of Western Sydney have discovered one of the largest black hole jets in the sky.
Spanning more than a million light-years from end to end, the jet shoots out of a black hole with enormous energy and at nearly the speed of light. But in the vast expanses of space between galaxies, it doesn’t always find its own way.
Just 93 million light-years away, the galaxy NGC2663 is in our neighborhood, cosmically speaking. If our galaxy were a house, NGC2663 would be a suburb or two away.
Looking at its starlight with an ordinary telescope, we see the familiar oval shape of a “typical” elliptical galaxy, with about ten times as many stars as our own Milky Way.
“Typical,” that is, until we observed NGC2663 with CSIRO’s Australian Square Kilometer Array Pathfinder (ASKAP) in Western Australia, a network of 36 linked radio antennas that form a single super telescope.
Radio waves reveal a jet of matter, ejected from the galaxy by a central black hole. This stream of high-powered material is about 50 times larger than the galaxy: if our eyes could see it in the night sky, it would be larger than the Moon.
While astronomers have found these types of jets before, NGC2663’s immense size (over a million light-years across) and relative proximity make these some of the largest known jets in the sky.
So what did they see when the precision and power of ASKAP obtained a “close-up” view (astronomically speaking!) of an extragalactic jet?
This research is led by Western Sydney University PhD student Velibor Velović, and has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society (preprint available here).
“Our Evolutionary Map of the Universe (EMU) study sees evidence of matter between galaxies pushing back on the sides of the jet,” he said.
This process is analogous to an effect seen in jet engines. As the exhaust plume passes through the atmosphere, ambient pressure pushes on it from the sides. This causes the jet to expand and contract, pulsing as it travels.
In addition to jet engines, crash diamonds have been seen in smaller, galaxy-sized aircraft. We have seen jets crash into dense clouds of gas, lighting them up as they go. But the constriction of the jets from the sides is a more subtle effect, making it more difficult to observe.
However, until NGC2663, we had not seen this effect on such huge scales.
This tells us that there is enough matter in intergalactic space around NGC2663 to push against the sides of the jet. In turn, the jet heats and pressurizes matter.
This is a feedback loop: intergalactic matter feeds a galaxy, the galaxy creates a black hole, the black hole launches a jet, the jet slows down the supply of intergalactic matter to the galaxies.
These jets affect the way gas forms in galaxies as the universe evolves. It is exciting to see such a direct illustration of this interaction.
The EMU survey, which is also responsible for identifying a new type of mysterious astronomical object called the “Odd Radius Circle,” continues to scan the sky. This remarkable radio jet will soon be joined by many more discoveries.
“As we do so, we will develop a better understanding of how black holes intimately shape the galaxies that form around them,” he said.
Original article published on The Conversation