- Black hole squirting out jets of particles
- Moving at almost 1 million km per hour
- Inflating a bubble in the surrounding gas
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 phenomenon, also known as a microquasar, blows a huge bubble of hot interstellar gas, 1,000 light-years across.
“We have been astonished by how much energy is injected into the gas by the black hole,” says Manfred Pakull.
“This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars 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.
The energy doesn’t actually come out of the black hole itself, but rather is emitted from the gas that is spiralling in towards the black hole.
Black hole “bubbles” in space
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 focused beams or jets of fast moving particles instead of radiation.
The fast particles 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 see the spots where the jets smash into the interstellar gas located around the black hole. Their observations show 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 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.”
More waiting to be found
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 black holes, 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 light-years away, in the outskirts of the spiral galaxy NGC 7793. From the size and expansion velocity of the bubble the astronomers have found that the jet activity must have been ongoing for at least 200,000 years.
The discovery is reported this week in the journal Nature.
Adapted from information issued by ESO / L. Calçada.
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