Monster Telescope Combo Spies Feeding Black Hole

Astronomers are finally getting a look at the extreme processes inside and around black holes. By combining the light from three powerful infrared telescopes, an international team has observed the active gas and dust accretion around a supermassive black hole in the center of a galaxy tens of millions of light-years away.

Resolving these features isn't just confirmation of how mass accretes onto black holes in centers of galaxies, it's how the image was taken is a major step in our Earth-bound exploration of the cosmos.

The team, led by Gerd Weigelt, a director of the Max Planck Institute for Radio Astronomy in Bonn, Germany, resolved the inner ring of debris in the inner region of the active galaxy NGC 3783.

They used the AMBER interferometry instrument of the ESO's Very Large Telescope Interferometer in Chile to combine the infrared light from three telescopes. Sebastian Hoenig, a postdoctoral researcher at the UC Santa Barbara Department of Physics, called the method "a major milestone toward directly imaging the growth phase of supermassive black holes."

Interferometry is an imaging method that uses two or more -- in this case, three -- separate points on a telescope array to observe an object. The light from the individual telescopes in combined or "interfered" to create a complete picture.

Since each individual image contains high-resolution information, the combined image can give astronomers stunning detail. With separate vantage points, the clarity of the final image is similar to the clarity of a telescope if its diameter were the same as the distance between the two points. In other words, this technique gives astronomers a spectacular view without the impossibly large hardware.

This method was necessary to see such a small object -- the ring-shaped distribution of hot dust called a torus in the inner region of the active galaxy NGC 3783. The dust torus has an angular radius of only 0.7 milliarcseconds in the sky. That's 5 million times smaller than one degree. To resolve something this small, astronomers would need a telescope with a mirror at least 100 meters in diameter. As we don't have the technology to build such a large telescope, interferometry was the best bet.

This method was able to achieve an angular resolution equivalent to the resolution of a telescope with a diameter of 130 meters, 15 times higher than one of the VLTI telescopes alone. Each telescope has a mirror 8 meters (26 ft) in diameter.

Read more at Discovery News