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A 300 parsec long jet-inflated bubble in NGC 7793

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 black hole is located in NGC 7793, a spiral galaxy in Sculptor.

"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 quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." The discovery is reported this week in the journal Nature.

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 interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometers per hour.

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!

"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."

This research will help astronomers understand the similarity between small black holes formed from exploded stars and the supermassive black holes at the centers 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.

(Download the research paper ESO1028).

ESO Press Release 1028

Recent news

top story: March newsletter of the ASSA Deep-Sky Section, featuring 47 Tuc on the cover. — "Nightfall" (2015 April) is the current newsletter of the Deep-Sky Observing Section of the Astronomical Society of Southern Africa.

A globular cluster in the realm of the galaxies — A rare gem - a bright globular cluster in the realm of the galaxies.

The Dark Emu rises, in pursuit of the Magellanic Clouds — The beautiful complex of dark nebulosity along the southern Milky Way appears like an ancient monster, its serpentine neck reaching out as if to gobble up the Magellanic Clouds.

Massive star forming region in the Small Magellanic Cloud — Dale Liebenberg images NGC 346, a gigantic star forming region in the SMC.

Flocculent Galaxy in Southern Leo — Dale Liebenberg images the spiral galaxy NGC 3521 in southern Leo.

Ancient open cluster in Lyra — Anthony Ayiomamitis images the old open cluster NGC 6791.

Golden Coin Galaxy — Dale Liebenberg images the Golden Coin, NGC 4945 in Centaurus.

NGC 2467 in Puppis — Dale Liebenberg images NGC 2467 in Puppis.

Last but not least - Messier 103 — Anthony Ayiomamitis images Messier 103 in Cassiopeia.

The Arkenstone of Thrain — Dale Liebenberg images Messier 22, the "Arkenstone of Thrain" according to Burnham.

ConCards available — A handy set of beginner's star charts, "Constellation Cards" are now available for free download.

Deep sky celebrations — Three deep sky observers of yore have birthdays this week: William Herschel (1738), the Fourth Earl of Rosse, and Stephane Javelle.

Necklace Nebula featured on APOD — The recently-discovered planetary nebula nicknamed the Necklace Nebula, recently featured on APOD.

Methuselah Nebula featured on APOD — The old bipolar planetary nebula MWP1, a.k.a. Methuselah Nebula, is today's APOD.

New deepsky book from CUP — Deep sky author Wolfgang Steinicke's latest book, "Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer's New General Catalogue", has just been published by Cambridge University Press.

NGC 1365 in infrared (ESO VLT) — The bright barred spiral galaxy NGC 1365 in Fornax has been imaged in the infrared with the ESO VLT telescope.

New HST image of eta Carinae Nebula — New observations, combined with images made in 2005, show beautiful detail in part of the extensive eta Carinae Nebula.

First planetary in open cluster found — A team of astronomers from Australia, the UK, the USA and France have discovered the first planetary nebula known to be associated with a galactic open cluster.

NGC 300 in Sculptor imaged at ESO — The bright spiral galaxy NGC 300 has been imaged with the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile.

Superwind galaxy NGC 4666 — A remarkable galaxy with very vigorous star formation has been newly imaged on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile.

News archives

All earlier news items can be browsed in the archives.

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