Scientists to 'see' black hole

Maxim would build an image of a black hole's accretion disk (Simulation by Benjamin Bromley)

Scientists think they can build an X-ray observatory that will for the first time allow them to "see" a black hole.

A million-fold increase in X-ray resolution will make distant objects appear as if they are in our Solar System

Prof Webster Cash

The researchers have successfully tested a small prototype which if scaled up could be a million times more powerful than today's observatories.

The experimental work is part of Nasa's Maxim mission. It aims to achieve a breakthrough in X-ray astronomy, which is used to probe some of the hottest and most violent events in the Universe.

But to get the resolution envisaged, Nasa would have to fly about 30 spacecraft in formation above the Earth.

Upper atmosphere

This is because Maxim would use a technique called X-ray interferometry, a process in which several small telescopes are connected together to mimic a very much larger device.

Current technology: Jets of particles shoot out from the core of galaxy M87, likely powered by a supermassive black hole

The approach has been employed by radio astronomers for several decades, separating dishes by many kilometres, to amplify and improve the sharpness of their images.

However, whereas radio waves can be detected at the Earth's surface, X-rays are absorbed by the upper atmosphere and detectors must be placed on balloons or satellites to get the necessary data.

The difficulty of focusing X-rays also means special cylindrical mirrors must be used to deflect incoming radiation on to detection points.

Dinner plate

In contrast, the new technology, developed by Professor Webster Cash, of the University of Colorado, US, and colleagues, uses multiple flat mirrors to gently steer the fringes of the incoming X-rays.

It will make it easier than previously thought to obtain a black hole image

Dr Nicholas White

Two sets of mirrors mix and amplify these beams, producing sharper images. The technology was tested with four mirrors in a vacuum tank to simulate conditions in space. The results are reported in the journal Nature.

Professor Cash said a fully scaled-up version of the design could resolve a region the size of a dinner plate on the surface of the Sun.

"A million-fold increase in X-ray resolution will make distant objects appear as if they are in our Solar System,'' he said. "This new approach allows X-ray astronomers to essentially jump from telescopes with resolution no finer than what an amateur uses in the backyard to an observatory far more precise than Hubble."

Superheated material

Commenting on the research, Dr Nicholas White, of Nasa's Goddard Space Flight Center, said: "This advance will allow us to directly observe effects predicted by Einstein's theory of general relativity under the most extreme gravity fields known."

He added: "It will make it easier than previously thought to obtain a black hole image."

Although black holes cannot by definition be imaged directly - the gravitational pull of a hole is so great not even light can escape from it - Maxim should make it possible to focus in sharply on the events in near space.

As material is dragged into a hole, it is accelerated and heated - the hottest parts will reach up to 100 million C and emit X-rays.

With the resolution promised by Maxim, astronomers would see details of the accretion process that are way beyond the detection of current observatories.

Nasa is considering launching Maxim spacecraft in two missions after 2010.