The global collaboration that delivered not one, but two images of supermassive black holes has now peeked into one of the brightest lights in the Universe.
The Event Horizon Telescope (EHT), a telescope array comprising radio antennas around the world, studied a distant quasar called NRAO 530, whose light has traveled 7.5 billion years to reach us.
The resulting data shows us the quasar engine in incredible detail and, astronomers say, will help us understand the complex physics of these incredible objects and how they generate such brilliant light.
Quasars – a term that is short for “quasi-stellar radio sources” – are a type of galaxy believed to be powered by a very active supermassive black hole at the center. That means the black hole is surrounded by material falling on it at breakneck speed.
Black holes themselves don’t emit light, but the material around an active black hole does. Gravity and friction cause the material to heat up and burn as it flows through the black hole like water down a drain. But that is not all.
Not all material falls into the black hole. Some of it is funneled and accelerated along magnetic field lines just outside the event horizon, the “point of no return,” beyond which even light cannot reach escape velocity.
When this material reaches the poles, it is launched into space as powerful jets of plasma, traveling at speeds of a significant percentage of the speed of light, known as relativistic speed. These thin, collimated jets also shine brightly… but we don’t fully understand how they are created and powered, and the role magnetic fields play.
Enter the EHT. It’s not an individual instrument or array, but a collaboration of radio telescope facilities from around the world combining to effectively form an Earth-sized radio telescope, something of an astronomy thing. Voltron.
This telescope is a powerful thing. In 2019, it gave humanity our first image of the event horizon of a black hole, the heart of a galaxy called M87 55 million light-years away. Then last year it delivered an image of the supermassive black hole at the center of our own Milky Way galaxy, Sagittarius A*.
Both images took years to make. The NRAO 530 observations actually took place in April 2017; the international team used it as a calibration target for imaging Sgr A*. This quasar is a popular calibration target for the center of the Milky Way, since the two objects appear quite close together in the sky.
It is those observations that a team, led by astronomers Svetlana Jorstad of Boston University and Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Germany, have now used to observe the heart of NRAO 530. Through such a great distance in the time and the space. , the researchers were able to see the heart of the quasar in unprecedented detail.
“The light we see traveled towards Earth over 7.5 billion years through the expanding Universe, but with the power of the EHT we see the details of the source’s structure on a scale as small as a single light-year.” Wielgus explains.
NRAO 530 is a rare type of quasar known as an “optically violent variable” quasar, and is known to have a powerful, highly relativistic jet. It is also categorized as a blazar; that is a blazar that is oriented in such a way that the jet is pointing directly or almost directly at us.
The research has been published in The Astrophysical Journal.https://iopscience.iop.org/article/10.3847/1538-4357/acaea8