An international team of astronomers in Chile employed three powerful telescopes to peer into the heart of a galaxy tens of millions of light years away.
The astronomers observed the hot accretion disk of matter falling into the supermassive black hole residing in the center of the galaxy with a method known as interferometry. This allowed the researchers to achieve incredible resolution on the mysterious happenings in the center of these active galactic nuclei (AGN).
Interferometry is a technique often employed in physics to observe minute differences in object length. By combining light from two or more sources, one may accurately probe tiny distances by studying the interference patterns generated by light following multiple paths.
Sebastian Hönig, a postdoctoral researcher in the UCSB Physics Dept., said that limitations on mirror size restrict the ability of astronomers to study objects that are extremely far from Earth.
“One of the big problems in astronomy is that if you want to look very deeply into some object or want to spatially resolve some far away object, you must have big telescopes, but we’re limited by the size of the mirror we can make; you can only go so big,” Hönig said.
Hönig said interferometry can achieve the resolution of a much more powerful telescope by combining the capabilities of weaker telescopes.
“You can combine two telescopes sitting next to each other, and you can actually achieve the resolution of a telescope that has the same size mirror as the distance between the two telescopes,” Hönig said. “For example, if you have two telescopes 100 meters away, you can simulate a telescopes with angular resolution of 100 meters. That’s really cool.”
Hönig was a member of the team that observed the galaxy (designated NGC 3783) using three-telescope interferometry, led by Gerd Weigelt, director of the Max Planck Institute for Radio Astronomy in Bonn, Germany.
The team used the Very Large Telescope Interferometer at the Paranal Observatory in Chile, operated by the European Southern Observatory.
Hönig explained that the team chose to observe NGC 3783 due to its geometric proportions and brightness.
“It’s one of the brightest we have in the southern hemisphere,” Hönig said. “It has a favorable geometry. In many objects you have dust that obscures the view to the center, but in this one you can look directly into the heart of the galaxy.
Astronomers are uniquely interested in AGN because they contain exceptionally large black holes. Studying the matter being consumed allows scientists a special opportunity to observe the life cycle of a black hole.
Matter falling into black holes generates star formation and facilitates star birth, leading to the hypothesis that galaxies may originate from black holes.
Hönig said interferometry is not a method typically used to study AGN.
“[AGN] are considered insane to do interferometry on, so we really hit the technical limit with this technique and with this instrument,” Hönig said. “This three-telescope interferometry is a major milestone toward directly imaging the growth phase of supermassive black holes.”