The Event Horizon Telescope is an Earth-sized virtual telescope powerful enough to see all the way to the center of our Milky Way, where a supermassive black hole will allow astrophysicists to put Einstein’s General Theory of Relativity to the test.

Astronomers, physicists and scientists from related fields across the world will convene in Tucson, Ariz. on Jan. 18 to discuss an endeavor that only a few years ago would have been regarded as nothing less than outrageous.

The conference is organized by Dimitrios Psaltis, an associate professor of astrophysics at the University of Arizona’s Steward Observatory, and Dan Marrone, an assistant professor of astronomy at Steward Observatory. “Nobody has ever taken a picture of a black hole,” Psaltis said. “We are going to do just that.”

(via Scientists Prepare to Take First-Ever Picture of a Black Hole | UANews.org)

As a quantum theory of gravity, loop quantum gravity could potentially solve one of the biggest problems in physics: reconciling general relativity and quantum mechanics. But like all tentative theories of quantum gravity, loop quantum gravity has never been experimentally tested. Now in a new study, scientists have found that, when black holes evaporate, the radiation they emit could potentially reveal “footprints” of loop quantum gravity, distinct from the usual Hawking radiation that black holes are expected to emit.

In this way, evaporating black holes could enable the first ever experimental test for any theory of quantum gravity. However, the proposed test would not be easy, since scientists have not yet been able to detect any kind of radiation from an evaporating black hole.

The scientists, from institutions in France and the US, have published their study called “Probing Loop Quantum Gravity with Evaporating Black Holes” in a recent issue of Physical Review Letters.

“For decades, Planck-scale physics has been thought to be untestable,” coauthor Aurélien Barrau of the French National Institute of Nuclear and Particle Physics (IN2P3) told PhysOrg.com. “Nowadays, it seems that it might enter the realm of experimental physics! This is very exciting, especially in the appealing framework of loop quantum gravity.”

In their study, the scientists have used algorithms to show that primordial black holes are expected to reveal two distinct loop quantum gravity signatures, while larger black holes are expected to reveal one distinct signature. These signatures refer to features in the black hole’s energy spectrum, such as broad peaks at certain energy levels.

Using Monte Carlo simulations, the scientists estimated the circumstances under which they could discriminate the predicted signatures of loop quantum gravity and those of the Hawking radiation that black holes are expected to emit with or without loop quantum gravity. They found that a discrimination is possible as long as there are enough black holes or a relatively small error on the energy reconstruction.

While the scientists have shown that an analysis of black hole evaporation could possibly serve as a probe for loop quantum gravity, they note that one of the biggest challenges will be simply detecting evaporating black holes.

“We should be honest: this detection will be difficult,” Barrau said. “But it is far from being impossible.”

(via Physicists propose test for loop quantum gravity)

unknownskywalker:

Astronomers Discover Medium-Sized Class of Black Holes

The new source HLX-1, the light blue object to the top left of the galactic bulge, is the ambassador for a new class of black holes, more than 500 times the mass of the Sun. It lies on the periphery of the edge-on spiral galaxy ESO 243-49, about 290 million light years from Earth.

Until now, identified black holes have been either super-massive (several million to several billion times the mass of the Sun) in the center of galaxies, or about the size of a typical star (between three and 20 solar masses).

The new discovery is the first solid evidence of a new class of medium-sized black holes and was made using the European Space Agency’s XMM-Newton X-ray space telescope. While it is widely accepted that stellar mass black holes are created during the death throes of massive stars, it is still unknown how super-massive black holes are formed.

It had been long believed by astrophysicists that there might be a third, intermediate class of black holes, with masses between a hundred and several hundred thousand times that of the Sun. However, such black holes had not been reliably detected until now.

One theory suggests that super-massive black holes may be formed by the merger of a number of intermediate mass black holes. To ratify such a theory, however, you must first prove the existence of intermediate black holes. This is the best detection to date of such long sought after intermediate mass black holes.

Using XMM-Newton observations carried out in 2004 and 2008, astronomers showed that HLX-1 displayed a variation in its X-ray signature. The huge radiance observed can only be explained if HLX-1 contains a black hole more than 500 times the mass of the Sun. The authors say that no other physical explanation can account for the data.

Image: This is an artist’s impression of the source HLX-1 (represented by the light blue object to the top left of the galactic bulge) in the periphery of the edge-on spiral galaxy ESO 243-49.

[Universe Today — The paper is available at Nature]

unknownskywalker:

Survey reveals many thousands of supermassive black holes

An international team of scientists, led by Penn State Distinguished Professor Donald Schneider, has announced its completion of a massive census in which they identified the quasars in one quarter of the sky.

The team’s work is part of the Sloan Digital Sky Survey (SDSS), a nearly decade-long discovery-and-research effort using a 2.5 meter telescope located at Apache Point Observatory in New Mexico. The completed catalog of quasars, includes 105,783 quasars, more than 96% of which were discovered by the SDSS.

Quasars are hundreds of times more luminous than our entire galaxy, yet they generate this tremendous power in regions similar in scale to that of our much smaller solar system. The best explanation of this extraordinary phenomenon is that we are witnessing the light energy emitted by material falling into black holes with masses of hundreds of millions of times, or even more than a billion times, that of our Sun.

The original goal for the SDSS was to determine the distances to over a million galaxies and 100,000 quasars. This was viewed as an extremely ambitious goal as, at the time we were designing the survey, fewer than 6,000 quasars had been identified. Clearly the goals have been exceeded for both galaxies and quasars.

Terabytes of image information had to be analyzed to identify quasar candidates, and the candidates had to be observed with spectrographs to determine whether or not they were indeed quasars.

In addition to the census itself, the quasar survey has made a number of key discoveries, including finding the most distant known objects in the universe and a number of gravitational lenses.

Image: The special-purpose telescope of the Sloan Digital Sky Survey is now engaged in a number of new astronomical surveys that will continue through 2014, ranging from the discovery of new planets to mapping the large-scale structure of the universe.

Source: The Pennsylvania State University [via]

Interesting…

unknownskywalker:

Supermassive Black Holes May Frequently Roam Galaxy Centers

A team of astronomy researchers at Florida Institute of Technology and Rochester Institute of Technology in the United States and University of Sussex in the United Kingdom, find that the supermassive black hole at the center of the most massive local galaxy, M87, is not where it was expected. Their research, conducted using the Hubble Space Telescope, concludes that the supermassive black hole in M87 is displaced from the galaxy center.

The most likely cause for this supermassive black hole to be off center is a previous merger between two older, less massive, supermassive black holes. The iconic M87 jet may have pushed the SMBH away from the galaxy center, say researchers.

At right is a large-scale image of galaxy M87 taken in 1998 with Hubble’s Wide-Field Planetary Camera 2. The two images at left show an image taken in 2006 with Hubble’s Advanced Camera for Surveys.

The position of the supermassive black hole is indicated by the black dot in the lower left panel, and a knot in the jet (HST-1), which was flaring in 2006. The red dot indicates the center of the galaxy’s light distribution, which is offset from the position of the black hole by about 22 light-years.

Source: Read the full story at Florida Institute of Technology (via HubbleSite.org)

physicsphysics:

zirkumflex:

A Journey into a Black Hole (via tdarnell)

Why yes, I would like to have my mind blown today, thank you!