Black hole blows big bubble

July 7, 2010
Combining observations done with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist's impression. Credit: ESO/L. Calçada

Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature.

"We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful and radio galaxies, which contain black holes with masses of a few million times that of the Sun."

Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings.

The astronomers could observe the spots where the jets smash into the located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour.

"The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto."

Astronomers do not have yet any means of measuring the size of the black hole itself. The smallest stellar black hole discovered so far has a radius of about 15 km. An average stellar black hole of about 10 solar masses has a radius of about 30 km, while a "big" stellar black hole may have a radius of up to 300 km. This is still much smaller than the jets, which extend out to several hundreds light years on each side of the black hole, or about several thousand million million km.

This research will help astronomers understand the similarity between small black holes formed from exploded stars and the supermassive black holes at the centres of galaxies. Very powerful jets have been seen from supermassive , but are thought to be less frequent in the smaller microquasar variety. The new discovery suggests that many of them may simply have gone unnoticed so far.

The gas-blowing black hole is located 12 million away, in the outskirts of the spiral galaxy NGC 7793. From the size and expansion velocity of the bubble the have found that the jet activity must have been ongoing for at least 200 000 years.

Explore further: Black Hole Blows Bubble Between The Stars

More information: These results appears in a paper published in this week's issue of the journal Nature ('A 300 parsec long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793, by Manfred W. Pakull, Roberto Soria and Christian Motch').

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4 / 5 (5) Jul 07, 2010
Not to be pedantic, but it is meaningless to speak of the "radius" of a black hole... because the radius of ANY black hole is infinite as measured from outside its event horizon, and no measurement performed inside the event horizon can be communicated to the outside Universe.

A black hole has a finite CIRCUMFERENCE, which is a function of the "Schwarzchild radius" that specifies the locus of its event horizon. But its RADIUS, measured along a geodesic that intersects the singularity, is infinite by definition.

Perhaps when the authors wrote "radius," they were referring to the Schwarzchild radius.
not rated yet Jul 07, 2010
Interesting. How does one determine the circumference of a black hole? I suspect that none are sufficiently close for direct observation.
5 / 5 (2) Jul 07, 2010
not rated yet Jul 07, 2010
i thought *puts on sinister voice* 'Nothing can excape, not even light' from a black hole, so how do they eject these radio lobes?

i'm a physics newbie but love reading about science and space.
1 / 5 (2) Jul 08, 2010
Don't feel dismayed you wouldn't be the only one confused by these findings. This is often the case when theory does not match what is observed. So now we have Black Holes, Dark Matter, Dark Energy, and now add in Dark Flow and still new observations are challenging these theories.

While it has been shown there is indeed very massive objects at the center of nearly every observed galaxy there are some serious problems with stating that those objects are indeed black holes.

The outermost planets speeds which are much higher than predicted appear to show a direct relationship with these massive objects.

Black hole theory always encounters the same troubling issue as BBT, the singularity.

Keep looking because I strongly suspect we will discover that these are not black holes at all but rather neutron stars anchoring galaxies.
5 / 5 (1) Jul 08, 2010
These radio lobes, jets, and what not are produced by the energy shed by the matter falling towards the black hole's center.
An incredible amount of energy can be released in this manner. Look up Active Galactic Nuclei. You'll find some interesting things.
not rated yet Jul 08, 2010
I thought the energy powering the jets came from magnetic fields embeded in the plasma created by collisions amongst in-falling particles of dust, etc. As the particles and plasma approach the event horizon they accelerate in a spiral path dragging the magnetic fields around with them. the magnetic fields in turn accelerate ions and electrons with a wip-like action. Or maybe the the discus thrower's action is a better analogy. As to why this results in jets from 'poles' of the rotating disc, I am not sure but I think it has to do with the lines of magnetic flux finding a lower density away from the disk. The entrained charged particles go that way too.

I understand that our Sun over its lifetime has reduced its angular momentum through a somewhat similar process.

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