News story

Black hole winds pull the plug on star formation

Herschel finds that winds from a giant black hole are sweeping away its host galaxy's reservoir of raw star-building material.

Black-hole wind sweeping away galactic gas.
Black-hole wind sweeping away galactic gas. Credit: ESA/ATG medialab.

Using Europe’s Herschel space observatory, astronauts have found that the winds blowing from a huge black hole are sweeping away its host galaxy’s reservoir of raw star-building material.

Supermassive black holes are extremely dense and compact, containing masses between millions and billions of times of that of our Sun. Located at the heart of most galaxies, many are relatively passive, like our own Milky Way. Others are devouring their surroundings.

These active black holes feed on nearby gas and expel powerful winds and jets. This may affect a galaxy’s star forming activity, causing it to slow down or possibly kill it entirely.

This is the first time a complete view of this process has been captured. Astronomers were able to detect winds very close to black holes using X-ray telescopes, and to trace larger galactic outflows of gas molecules through infrared observations, but had not succeeded in finding them both in the same galaxy.

Combining infrared observations from the Herschel space observatory with the new data from the Sazaku X-ray satellite, astronomers detected the winds close to the central black hole. They also detected the winds pushing galactic gas away in a galaxy known as IRAS F11119+3257.

The winds start small and fast at 25% the speed of light near the black hole, blowing away the equivalent of one solar mass of gas every year. The winds slow down as they progress outwards and push away an additional few hundred solar masses of gas molecules a year. This first solid proof that black-hole winds are stripping their host galaxies of gas supports the view that black holes can potentially stop stars forming in their host galaxies.

Herschel has already revolutionised our understanding of how stars are born. This new result is now helping us understand why and how a star formation is some galaxies can be globally affected and even switch off entirely,

Göran Pilbratt, Herschel Project Scientist at ESA.

Despite being switched off on 17 June 2013, Herschel is the largest infrared space observatory, collecting data from unexplored wavelengths of light in the far infrared region of the electromagnetic spectrum. Launched 14 May 2009, Herschel examines the formation of galaxies and stars. The UK led the development of the SPIRE (Spectral and Photometric Imaging Receiver) instrument which was developed by an international consortium. It was led by a Principal Investigator from Cardiff University and was tested and assembled at the STFC Rutherford Appleton Laboratory (RAL) in Oxfordshire.

There have been many UK institues involved in SPIRE, such as Imperial College London, University College London’s Mullard Space Science Laboratory and the UK Astronomy Technology Centre, Edinburgh. UK companies involved in the mission include AEA Technology, Analyticon, BOC Edwards, Datasat, MT Satellite Products and System International.

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Published 1 April 2015