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Gales of gases whipping through the universe are dimming galaxies, researchers have discovered.

Astronomers found the bright core of a spiral galaxy 245 million light years away has unexpectedly lost more X-ray radiation than expected because of the strong winds.

And these, in turn, mean the winds are able to spread through the superhot disk surrounding a black hole at speeds five times faster than was predicted.

Astronomers have discovered strange and unexpected behaviour around the supermassive black hole at the heart of the galaxy NGC 5548. The researchers detected a clumpy gas stream originating in a superheated region called a quasar (illustration shown) flowed outwards and enabled fast winds to form

Wind storms of up to 620 miles (1,000km) per second are known in galaxies, but the new study found they can blow up to 3,100 miles (5,000km) per second.

The observations were made in the nucleus of galaxy NGC 5548, which contains a region of powerful X-ray light surrounding the galaxy's central black hole.

But the winds, rarely seen in the heart of this type of galaxy, cast new light on the poorly-understood processes about the interaction between galaxies and their central black holes.

The study, published in Science Express, provides the first direct evidence for the long-predicted shielding process needed to accelerate powerful gas streams, or 'winds,' to high speeds.

Almost all galaxies are thought to have supermassive black holes at their centres, but most are dormant as they have very little material near them.

In some galaxies, however, gas, dust and even stars are close enough to the black hole to fall into it and they encircle the black hole in a superhot region known as a quasar.

Astronomers call these 'active galaxies,' as the matter spiralling into the black hole forms the disk-shaped quasar that heats up and shines extremely brightly, emitting radiation, including X-rays and ultraviolet.

The ultraviolet radiation can launch winds outward, which may be so strong that they can blow off gas that would have otherwise fallen onto the black hole, slowing its growth down again.

This feedback mechanism means black hole winds can regulate both the growth of a black hole and its host galaxy.

But the winds only come into existence if their starting point is shielded from X-rays.

This artist's impression illustrates the finding, by an international team of astronomers, of the flowing outward from the supermassive black hole at the centre of active galaxy NGC 5548, with the arrow showing the line of sight of the observations. The gas filament blocked 90 per cent of the X-rays emitted from the black hole

The newly discovered stream of gas in the galaxy NGC 5548 - the first of its kind in one of the best-studied active galaxies - provides this protection, and it appears that the shielding has been going on for at least three years.

'This is a milestone in understanding the interaction of supermassive black holes and their host galaxies,' said Professor Graziella Branduardi-Raymont from University College London's Mullard Space Science Laboratory.

'I was delighted when our consortium agreed to focus the campaign on NGC 5548, as I first became interested in this active galaxy almost three decades ago, observing it with the X-ray instruments operating in space at the time.'

Supermassive black holes in the nuclei of active galaxies, such as NGC 5548, are known to expel large amounts of matter through powerful winds of ionised gas.

This is the galaxy known as NGC 5548. At its heart, though not visible here, is a supermassive black hole behaving in a strange and unexpected manner. Wind storms of up to 620 miles (1,000km) per second are known in galaxies, but this new study found they can blow up to 3,100 miles (5,000km) per second

The persistent wind of NGC 5548, known for two decades, reaches speeds exceeding 620 miles (1,000km) per second.

But now a new obscuring wind has arisen, much stronger and faster than the persistent wind.

'The new wind reaches speeds of up to 5,000 kilometres [3,100 miles] per second but is much closer to the nucleus than the persistent wind,' said Dr Jelle Kaastra, of the Netherlands Institute for Space Research.

"The new gas outflow blocks 90 per cent of the low-energy X-rays that come from very close to the black hole, and it obscures up to a third of the region that emits the ultraviolet radiation at a few light-days distance from the black hole.'

Because of this shielding, the persistent wind far away from the nucleus receives less radiation and cools down.

This causes new features to arise in the spectrum of the wind detected, allowing researchers to pinpoint the location of the strongest persistent wind component.

Ultimately the research could herald new insights into how supermassive black holes interact with the galaxies they inhabit.