Muse on X-rays: Supermassive black hole

X-ray jet

A supermassive black hole 12.4 billion light years from Earth is pumping out a jet of X-rays that could give astronomers using NASA's Chandra X-ray Observatory a glimpse into how such bodies form and the role they play in galaxy formation in the early universe.

The X-ray jet is observed in the quasar GB 1428+4217 (GB 1428) and the enormous black hole from which it emerges is presumed to be at the centre of this incredibly distant galaxy, pulling in matter at such a high rate that the characteristic quasar phenomena arise. Astronomers now consider it most likely that a supermassive black hole is at the centre of every galaxy, while much smaller and weaker black holes exist scattered throughout galaxies but not having the powerful effects of a supermassive on the galaxy as a whole. 

A long time ago...

The origins of X-rays from black holes is due to the energy being released as matter falls towards the black hole and particulate radiation is emitted at close to the speed of light, which then interact with magnetic fields and the ubiquitous microwave photons left behind after the Big Bang, to generate the X-rays. Of course, we are observing a phenomenon the radiation from which was emitted at a time when the universe was a tenth of the age it is now, a mere 1.3 billion years after the Big Bang, and the background radiation was of much higher energy, a thousand-fold more intense in fact. Some astronomers have described black holes as being Einstein's famous energy-matter equivalence theory incarnate as they are the most efficient systems known for converting matter into energy; far more efficient than the nuclear fusion processes occurring in stars. The conversion of matter into X-rays by this distant supermassive black hole is a case in point.

"We're excited about this result not just because it's a record holder, but because very few X-ray jets are known in the early universe," explains Teddy Cheung of the National Academy of Sciences, who is resident at the Naval Research Laboratory in Washington DC. "Since the brightness of the jet in X-rays depends, among other things, on how fast the electrons are moving away from the black hole, discoveries like the jet in GB 1428 tell us something about the environment around supermassive black holes and their host galaxies not that long after the Big Bang," add team member Lukasz Stawarz of the Japan Aerospace Exploration Agency in Kanagawa, Japan.

The background radiation is a fortuitous natural amplifier of the emissions allowing astronomers to observe the X-ray jets despite the vast distances the radiation must travel to reach Chandra and the huge quantities of dimming cosmic dust in between. However, the X-rays in the jet may not necessarily be generated in this way. It is possible that they are the radiation generated by electrons spiralling around magnetic field lines in the jet. This, the team says, is less likely as the jet is so bright that amplification by the background radiation must be invoked. 

...in a galaxy far, far away

The previous record holder was an X-ray jet seen at 12.2 billion light years away and before that one at 12 billion light years, discovered by the same team. The researchers estimate that the jet in GB 1428 is at least 230,000 light years, or about twice the diameter of the entire Milky Way galaxy. The NSF's Very Large Array (VLA) and others around the globe have also observed a similar shaped jet in GB 1428 at radio wavelengths. Calculations based on this data and additional Chandra observations suggest that the jet is pointing directly at Earth. A much smaller jet, just 1900 light years long, points in a similar direction to the X-ray jet.

The research team included Doug Gobeille of the University of South Florida in Tampa, John Wardle of Brandeis University, Waltham, Massachusetts, Dan Harris and Dan Schwartz from the Harvard-Smithsonian Center for Astrophysics.