Black hole “Doughnut” theory – a big mistake

May 29th, 2014, Published in Articles: EngineerIT

 

Information collected by the Wide-field Infrared Survey Explorer (WISE) does not corroborate the black hole doughnut  theory. Researchers found evidence that something other than a doughnut structure may, in some circumstances, determine whether a black hole is visible or hidden. The team has not yet determined what this may be, but the results suggest the unified, or doughnut, model does not have all the answers.

WISE scans the entire sky in infrared light, picking up the glow of hundreds of millions of objects and producing millions of images. The mission has  uncovered objects never seen before, including the coolest stars, the universe’s most luminous galaxies and some of the darkest near-Earth asteroids and comets. Its vast catalogues will help answer fundamental questions about the origins of planets, stars and galaxies, and provide a huge amount of data for astronomers to work on for decades to come. Thanks to next-generation technology, WISE’s sensitivity is hundreds of times greater than its predecessor, the Infrared Astronomical Satellite, which operated in 1983.  While WISE was put into hibernation in 2011 after scanning Earth’s entire sky twice it was reactivated in 2013, renamed NEOWISE, and given a new mission to identify potentially hazardous near-Earth objects. However scientists are still actively combing public data from WISE.

This image shows galaxies clumped together in the Fornax cluster, located 60 million light-years from Earth. The picture was taken by WISE, but has been artistically enhanced to illustrate the idea that clumped galaxies will, on average, be surrounded by larger halos of dark matter (purple). Image Credit: NASA/JPL-Caltech

This image shows galaxies clumped together in the Fornax cluster, located 60-million light-years from Earth. The picture was taken by WISE, but has been artistically enhanced to illustrate the idea that clumped galaxies will, on average, be surrounded by larger halos of dark matter (purple). Image Credit: NASA/JPL-Caltech

A survey of more than 170 000 supermassive black holes, using NASA’s WISE, has astronomers re-examining a decades-old theory about the varying appearances of these interstellar objects.

The unified theory of active, supermassive black holes, first developed in the late 1970s, was created to explain why black holes, though similar in nature, can look completely different. Some appear to be shrouded in dust, while others are exposed and easy to see.

The unified model attempted to answer this question by proposing that every black hole is surrounded by a dusty, doughnut-shaped structure called a torus. Depending on how these “doughnuts” are oriented in space, the black holes will take on various appearances. For example, if the doughnut is positioned so that we see it edge-on, the black hole is hidden from view. If the doughnut is observed from above or below, face-on, the black hole is clearly visible.

WISE in the clean room before it was launched

WISE in the clean room before it was launched.

However recent findings revealed a new feature about active black holes not known before.  “The details remain a mystery,” said Lin Yan of NASA’s Infrared Processing and Analysis Centre (IPAC), based at the California Institute of Technology in Pasadena. “We hope our work will inspire future studies to better understand these fascinating objects.”

Every galaxy has a massive black hole at its heart. The new study focuses on the “feeding” ones, called active, supermassive black holes, or active galactic nuclei. These black holes gorge on surrounding gas material that fuels their growth.

With the aid of computers, scientists were able to pick out more than 170,000 active supermassive black holes from the WISE data. They then measured the clustering of the galaxies containing both hidden and exposed black holes — the degree to which the objects clump together across the sky.

If the unified model was true, and the hidden black holes are simply blocked from view by doughnuts in the edge-on configuration, then researchers would expect them to cluster in the same way as the exposed ones. According to theory, since the doughnut structures would take on random orientations, the black holes should also be distributed randomly.

WISE found something totally unexpected. The results showed the galaxies with hidden black holes are more clumped together than those of the exposed black holes. If these findings are confirmed, scientists will have to adjust the unified model and come up with new ways to explain why some black holes appear hidden.

Another way to understand the WISE results involves dark matter. Dark matter is an invisible substance that dominates matter in the universe, outweighing the regular matter that makes up people, planets and stars. Every galaxy sits in the centre of a dark matter halo. Bigger halos have more gravity and, therefore, pull other galaxies toward them.

Because WISE found that the obscured black holes are more clustered than the others, the researchers know those hidden black holes reside in galaxies with larger dark matter halos. Though the halos themselves would not be responsible for hiding the black holes, they could be a clue about what is occurring.

The unified theory was proposed to explain the complexity of what astronomers were seeing. It seems that the simple model may have been too simple. As Albert Einstein said, models should be made ‘as simple as possible, but not simpler.

This article was compiled from various NASA and JPL sources.

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