Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Deep X-ray surveys reveal black hole population, glimpse at the universe


Data from X-ray observatory surveys show that black holes are much more numerous and evolved differently than researchers would have expected, according to a Penn State astronomer.

"We wanted a census of all the black holes and we wanted to know what they are like," says Dr. Niel Brandt, professor of astronomy and astrophysics. "We also wanted to measure how black holes have grown over the history of the Universe."

Brandt and other researchers have done just that by looking at a patch of sky in the Northern hemisphere called the Chandra Deep Field-North, using NASA’s Chandra X-ray Observatory and a similar patch in the Southern hemisphere called the Extended Chandra Deep Field-South. Surveys are also being carried out in other parts of the sky using both Chandra and the European Space Agency’s X-ray Multi-Mirror Mission-Newton.

The researchers looked at X-ray emissions because areas around black holes emit X-rays as well as visible light. The penetrating nature of X-rays provides a direct way to identify the black holes. Using X-rays also enables astronomers to pinpoint the black holes at the centers of galaxies without their signal being washed out by the visible light coming from a galaxy’s stars, Brandt told attendees at the annual meeting of the American Association for the Advancement of Science in St. Louis, Mo. today, (Feb. 17). The black holes they studied were those that reside at the centers of galaxies and are actively emitting X-rays, therefore they are called active galactic nuclei.

"We find active Super Massive Black Holes at the centers of massive galaxies," says Brandt. "Our Galaxy also has its own black hole at its center measuring 2.6 million solar masses. Our black hole is not active today, but we presume it was active in the past."

These deep, extragalactic X-ray surveys looked at carefully chosen patches of sky, that are largely free of anything that might interfere with obtaining the X-ray data. Chandra looked at the Chandra Deep Field-North – an area of sky two thirds the size of the full Moon – for the time span of 23 days over a two-year period. The researchers detected about 600 X-ray sources. After comparing the X-ray images with optical images of exactly the same slice of sky taken by the Hubble Space Telescope, nearly all 600 point sources corresponded to optical galaxies, suggesting that the black holes that were sources for the X-ray signature were in the centers of galaxies.

"X-ray astronomers are doing better than anyone else by about a factor of ten, in identifying these active galactic nuclei" says Brandt. "With more time we could do even better, going even deeper."

What the researchers found was that Super Massive Black Holes are more numerous than we might have expected. They also found that black holes evolved differently than astronomers expected prior to the Chandra work. Extrapolating from the 600 black holes found by Chandra, Brandt suggests that there are about 300 million Super Massive Black Holes in the whole sky.

The existence of so many black holes, confirmed that what was once thought to be a truly diffuse Cosmic X-ray Background Radiation, actually comes from point sources.

In the 1960s, astronomers discovered quasars, very distant, highly luminous black holes, in galactic centers. Quasars, initially called quasi-stellar radio sources, were studied intensely. Researchers soon realized that only some of these objects were radio emitters and that they formed early in the history of the Universe.

"While quasars are spectacular, they are not representative of typical active galactic nuclei," says Brandt. "Now, using Chandra and other X-ray observatories, we can find and study the moderate-luminosity, typical active galactic nuclei in the distant, high-redshift Universe."

Quasars and moderate-luminosity active galactic nuclei also evolved differently. Quasars are a phenomenon of young galaxies, while moderate-luminosity, active galactic nuclei peaked later in cosmic time.

"We would like to know if active galactic nuclei change over cosmic time," says Brandt. "Do black holes feed and grow in the same way over the history of the Universe?"

Researchers looked at the relative amount of power coming out in X-rays compared to other wavelengths and found that this ratio does not change over 13 billion years of time. They looked at the X-ray spectra and found that these also did not change through time.

"Despite the enormous changes in the space density of back holes, the individual engines powering active galactic nuclei are remarkably stable," Brandt said.

Brandt believes that Chandra could observe the Chandra Deep Field-North for a longer period of time and obtain more sensitive, deeper data. This would bring to light galaxies that are currently obscured. It would also gather more X-rays allowing better X-ray spectral and variability analyses. With more sensitive probing, the researchers are also detecting an increasing number of non-active galaxies like our own.

"Chandra has worked well for six years now," says Brandt. "There is no reason why Chandra and Newton cannot continue to observe for another 10 or more years."

A’ndrea Elyse Messer | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Seeking balanced networks: how neurons adjust their proteins during homeostatic scaling.

24.10.2016 | Life Sciences

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

More VideoLinks >>>