Very Large Telescope details gas clouds at the center of the first quasar

Nov. 30 (UPI) -- Using the Very Large Telescope's GRAVITY instrument, scientists have observed the clouds swirling at the center of a faraway quasar.

The observations, published this week in the journal Nature, are the first to characterize the gas clouds surrounding a black hole outside of the Milky Way.

The object described in the new paper is 3C 273, the first quasar described in the scientific literature. The distant object was spotted by astronomer Maarten Schmidt in 1963.

Quasars are the active nuclei at the center of distant galaxies. The extremely luminous objects are formed by the accretion disk that surrounds supermassive black holes. As gas and dust are pulled in by the black hole, the material is squeezed to extreme densities, giving off significant amounts of energy.

"Quasars are among the most distant astronomical objects that can be observed," Hagai Netzer, an astrophysicist at Tel Aviv University, said in a news release. "They also play a fundamental role in the history of the universe, as their evolution is intricately tied to galaxy growth. While almost all large galaxies harbor a massive black hole at their centers, so far only one in our Milky Way has been accessible for such detailed studies."

Using VLT's GRAVITY instrument, scientists were able to observe the glowing accretion disk at the center of 3C 273.

The GRAVITY instrument combines the observations all four ESO VLT telescopes, a method called interferometry. The technique enables a significant gain in angular resolution, replicating the power and precision of a much larger telescope.

"GRAVITY allowed us to resolve, for the first time ever, the motion of gas clouds around a central black hole," said Eckhard Sturm, researcher at the Max Planck Institute for Extraterrestrial Physics, or MPE.

"This is the first time that we can spatially resolve and study the immediate environs of a massive black hole outside our home galaxy, the Milky Way," said Reinhard Genzel, head of the infrared research group at MPE. "Black holes are intriguing objects, allowing us to probe physics under extreme conditions -- and with GRAVITY we can now probe them both near and far."

Because the swirling gas clouds at the center of 3C 273 occupy a relatively small amount of space and are located 2.5 billion light-years from Earth, they're difficult to observe.

"Broad emission lines created by gas in the vicinity of the black hole are observational hallmarks of quasars," Netzer said. "Until now, the distance of the gas from the black hole, and occasionally the pattern of the motion, could only be measured by an older method that made use of light variations in the quasars,"

GRAVITY allowed for observations at much higher resolutions, and researchers were able to use the new observations to estimate the quasar's mass.

"For the first time, the old method was tested experimentally and passed its test with flying colors, confirming previous estimates of about 300 million solar masses for the black hole," said Jason Dexter of MPE.