Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Black Holes Grow Big by Eating Stars

03.04.2012
Most galaxies, including the Milky Way, have a supermassive black hole at their center weighing millions to billions of suns. But how do those black holes grow so hefty? Some theories suggest they were born large. Others claim they grew larger over time through black hole mergers, or by consuming huge amounts of gas.
New research by astronomers at the University of Utah and the Harvard-Smithsonian Center for Astrophysics (CfA) shows that supermassive black holes can grow big by ripping apart double-star systems and swallowing one of the stars.

"Black holes are very efficient eating machines," said Scott Kenyon of the CfA. "They can double their mass in less than a billion years. That may seem long by human standards, but over the history of the Galaxy it's pretty fast."

"I believe this has got to be the dominant method for growing supermassive black holes," added lead author Benjamin Bromley of the University of Utah. The study was published in the April 2 online edition of The Astrophysical Journal Letters.

Their work follows up on the 2005 discovery, by a team of CfA astronomers led by Warren Brown, of hypervelocity stars - stars that were flung out of the galactic center by gravitational forces and are traveling fast enough to escape the Milky Way.

Hypervelocity stars originate from a binary star system that wanders too close to the Milky Way's central black hole. Tidal forces capture one star and eject the other. The star that is captured into orbit around the black hole later becomes fodder for the galactic monster.

"We put the numbers together for observed hypervelocity stars and other evidence, and found that the rate of binary encounters [with our galaxy's supermassive black hole] would mean most of the mass of the galaxy's black hole came from binary stars," Bromley says. "We estimated these interactions for supermassive black holes in other galaxies and found that they too can grow to billions of solar masses in this way."

As many as half of all stars are in binary pairs, so they are plentiful in the Milky Way and other galaxies.

The new study looked at each step in the process of a supermassive black hole eating binary stars, and calculated what would be required for the process to match observations. Their simulations accurately predicted the rate at which hypervelocity stars are produced (one every 1,000 to 100,000 years). The theory also fit the rate of "tidal disruption events" observed in other galaxies, which happen when stars are shredded and pulled into supermassive black holes.

Their theory shows that the Milky Way's supermassive black hole has doubled to quadrupled in mass during the past 5 billion to 10 billion years by eating stars.

"When we look at observations of how stars are accumulating in our galactic center, it's clear that much of the mass of the black hole likely came from binary stars that were torn apart," said Bromley.

This release is being issued jointly with the University of Utah.
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Lee Siegel, Univ. of Utah
801-581-8993
lee.siegel@utah.edu

Christine Pulliam | EurekAlert!
Further information:
http://www.utah.edu
http://www.cfa.harvard.edu

More articles from Physics and Astronomy:

nachricht The taming of the light screw
22.03.2019 | Max-Planck-Institut für Struktur und Dynamik der Materie

nachricht Magnetic micro-boats
21.03.2019 | Max-Planck-Institut für Polymerforschung

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: The taming of the light screw

DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.

The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Laser processing is a matter for the head – LZH at the Hannover Messe 2019

25.03.2019 | Trade Fair News

A Varied Menu

25.03.2019 | Life Sciences

‘Time Machine’ heralds new era

25.03.2019 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>