Chandra finds black holes are 'green'

Apr 24, 2006
Chandra finds black holes are 'green'
Credit: X-ray: NASA/CXC/KIPAC/S.Allen et al; Radio: NRAO/VLA/G.Taylor; Infrared: NASA/ESA/McMaster Univ./W.Harris

Black holes are the most fuel efficient engines in the Universe, according to a new study using NASA's Chandra X-ray Observatory. By making the first direct estimate of how efficient or "green" black holes are, this work gives insight into how black holes generate energy and affect their environment.

The new Chandra finding shows that most of the energy released by matter falling toward a supermassive black hole is in the form of high-energy jets traveling at near the speed of light away from the black hole. This is an important step in understanding how such jets can be launched from magnetized disks of gas near the event horizon of a black hole.

"Just as with cars, it's critical to know the fuel efficiency of black holes," said lead author Steve Allen of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and the Stanford Linear Accelerator Center. "Without this information, we cannot figure out what is going on under the hood, so to speak, or what the engine can do."

Allen and his team used Chandra to study nine supermassive black holes at the centers of elliptical galaxies. These black holes are relatively old and generate much less radiation than quasars, rapidly growing supermassive black holes seen in the early Universe. The surprise came when the Chandra results showed that these "quiet" black holes are all producing much more energy in jets of high-energy particles than in visible light or X-rays. These jets create huge bubbles, or cavities, in the hot gas in the galaxies.

The efficiency of the black hole energy-production was calculated in two steps: first Chandra images of the inner regions of the galaxies were used to estimate how much fuel is available for the black hole; then Chandra images were used to estimate the power required to produce the cavities.

"If a car was as fuel-efficient as these black holes, it could theoretically travel over a billion miles on a gallon of gas," said coauthor Christopher Reynolds of the University of Maryland, College Park.

New details are given about how black hole engines achieve this extreme efficiency. Some of the gas first attracted to the black holes may be blown away by the energetic activity before it gets too near the black hole, but a significant fraction must eventually approach the event horizon where it is used with high efficiency to power the jets. The study also implies that matter flows towards the black holes at a steady rate for several million years.

"These black holes are very efficient, but it also takes a very long time to refuel them," said Steve Allen who receives funding from the Office of Science of the Department of Energy.

This new study shows that black holes are green in another important way. The energy transferred to the hot gas by the jets should keep hot gas from cooling, thereby preventing billions of new stars from forming. This will place limits on the growth of the largest galaxies, and prevent galactic sprawl from taking over the neighborhood.

Source: Chandra X-ray Center

Explore further: Bacteria manipulate salt to build shelters to hibernate

add to favorites email to friend print save as pdf

Related Stories

Black hole fireworks in nearby galaxy

Jul 03, 2014

(Phys.org) —Celebrants this Fourth of July will enjoy the dazzling lights and booming shock waves from the explosions of fireworks. A similarly styled event is taking place in the galaxy Messier 106, as ...

Chandra captures galaxy sparkling in X-rays

Jun 03, 2014

(Phys.org) —Nearly a million seconds of observing time with NASA's Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way glittering with hundreds of X-ray points of light.

Recommended for you

Bacteria manipulate salt to build shelters to hibernate

4 hours ago

For the first time, Spanish researchers have detected an unknown interaction between microorganisms and salt. When Escherichia coli cells are introduced into a droplet of salt water and is left to dry, b ...

How do we terraform Venus?

4 hours ago

It might be possible to terraform Venus some day, when our technology gets good enough. The challenges for Venus are totally different than for Mars. How will we need to fix Venus?

Biomarkers of the deep

6 hours ago

Tucked away in the southwest corner of Spain is a unique geological site that has fascinated astrobiologists for decades. The Iberian Pyrite Belt (IPB) in Spain's Río Tinto area is the largest known deposit ...

Image: Chandra's view of the Tycho Supernova remnant

7 hours ago

More than four centuries after Danish astronomer Tycho Brahe first observed the supernova that bears his name, the supernova remnant it created is now a bright source of X-rays. The supersonic expansion of ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

jeffsaunders
not rated yet May 29, 2009
A confusing article. I get the impression though, in the end, that what they are saying is that most of the matter that falls towards the black hole is blasted back out again in high energy particles.



At least that is what I think they are saying, in which case I would have labeled the black hole as very inefficient, as it hardly absorbs any of the matter it attracts.



I guess, like most things, it depends on your point of view and motivation. Is a black hole more efficient if it grows faster or slower?