Three-telescope interferometry allows astrophysicists to observe how black holes are fueled

May 16, 2012
This is an artist's view of a dust torus surrounding the accretion disk and the central black hole in active galactic nuclei. Credit: NASA E/PO - Sonoma State University, Aurore Simonnet (http://epo.sonoma.edu/)

(Phys.org) -- By combining the light of three powerful infrared telescopes, an international research team has observed the active accretion phase of a supermassive black hole in the center of a galaxy tens of millions of light years away, a method that has yielded an unprecedented amount of data for such observations. The resolution at which they were able to observe this highly luminescent active galactic nucleus (AGN) has given them direct confirmation of how mass accretes onto black holes in centers of galaxies.

"This three-telescope interferometry is a major milestone toward directly imaging the growth phase of supermassive ," said Sebastian Hoenig, a postdoctoral researcher at the UC Santa Barbara Department of Physics, and one of the who utilized this technique to observe the AGN at the center of galaxy NGC 3783. The observation was led by Gerd Weigelt, a director of the Max Planck Institute for in Bonn, Germany.

Hoenig described their findings as a ring of hot dust that marks the transition from a more-distant mixture of gas and dust in a toroidal (doughnut-shaped) structure, to a gaseous disk closer to the black hole. The dusty part, he said, is interesting because it dominates the of active galactic nuclei and can be easily observed.

However, observing the ring of hot dust in NGC 3783 was a challenge for the astrophysicists. Not only is the ring distant and faint, but the ability of individual infrared telescopes to resolve distances between actively accreting objects is also highly limited. Even the largest optical/ in the world, the Keck telescopes, were not powerful enough, though they can show objects in the infrared comparable to about the size of a football field at the distance of the moon.

This is the Very Large Telescope Interferometer at the ESO/Paranal Observatory in Chile. Credit: Sebastian Hoenig

"In order to spatially resolve the accretion process onto supermassive black holes in , we have to be at least a factor of ten better," said Hoenig. To achieve that angular resolution in a single telescope, it would have to be 130 meters in diameter.

However, by using the AMBER interferometry instrument to simultaneously combine the light from three 8-meter telescopes at the Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile, the research team was able to achieve the angular resolution needed to observe the hot dust ring. The Paranal Observatory is operated by the European Southern Observatories (ESO).

The combination of the light from the three telescopes was no small feat, as the tiny differences in the arrival of light in the individual telescopes have to undergo constant correction with an accuracy of a few micrometers – roughly ten times smaller than the thickness of a hair, according to Hoenig.

"The ESO VLTI provides us with a unique opportunity to improve our understanding of ," said lead researcher Weigelt. "It allows us to study fascinating physical processes with unprecedented resolution over a wide range of infrared wavelengths. This is needed to derive physical properties of these sources."

Up next for the research team, which also includes astrophysicists from the universities of Florence, Grenoble, and Nice, will be the continued accumulation of information from additional observations toward a highly detailed image of the active at galaxy NGC 3783.

"Our main interest is to learn how supermassive black holes in the centers of galaxies are fueled, so that they grow to the enormous million to billion solar mass objects we see today," said Hoenig.

Explore further: Finding hints of gravitational waves in the stars

Related Stories

Galaxy Collision Switches on Black Hole

Dec 10, 2009

(PhysOrg.com) -- This composite image of data from three different telescopes shows an ongoing collision between two galaxies, NGC 6872 and IC 4970.

Small distant galaxies host supermassive black holes

Sep 15, 2011

(PhysOrg.com) -- Using the Hubble Space Telescope to probe the distant universe, astronomers have found supermassive black holes growing in surprisingly small galaxies. The findings suggest that central black ...

Recommended for you

Image: NGC 6872 in the constellation of Pavo

5 hours ago

This picture, taken by the NASA/ESA Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused ...

Measuring the proper motion of a galaxy

6 hours ago

The motion of a star relative to us can be determined by measuring two quantities, radial motion and proper motion. Radial motion is the motion of a star along our line of sight. That is, motion directly ...

Gravitational waves according to Planck

23 hours ago

Scientists of the Planck collaboration, and in particular the Trieste team, have conducted a series of in-depth checks on the discovery recently publicized by the Antarctic Observatory, which announced last ...

Infant solar system shows signs of windy weather

23 hours ago

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have observed what may be the first-ever signs of windy weather around a T Tauri star, an infant analog of our own Sun. This may help ...

Finding hints of gravitational waves in the stars

Sep 22, 2014

Scientists have shown how gravitational waves—invisible ripples in the fabric of space and time that propagate through the universe—might be "seen" by looking at the stars. The new model proposes that ...

How gamma ray telescopes work

Sep 22, 2014

Yesterday I talked about the detection of gamma ray bursts, intense blasts of gamma rays that occasionally appear in distant galaxies. Gamma ray bursts were only detected when gamma ray satellites were put ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

maxwallis
1 / 5 (1) May 17, 2012
Why ignore other concepts than 'Black Holes' for gravitationally collapsed supermassive objects, which likewise explain the power source for AGNs through accreting mass? see "Stellar collapse in field theories of gravitation" 2010 journalofcosmology.com/MarshallWallis.pdf
"Likely formation of general relativistic radiation pressure supported stars or eternally collapsing objects Mitra+Glendinning Mon. Not. R. Astron. Soc.(2010)