You probably know that a black hole has gravity so strong that not even light can escape, but not everyone realizes that the largest black holes, like those at the center of galaxies, also spew matter back out. In the case of galaxy NGC 5548, the supermassive black hole at its center was observed to have a persistent wind of ionized gases coming out at 621 miles per second (1000 km/s), but that’s nothing compared to what was just discovered.
Newly detected winds reach 3000 miles per second
“These new winds reach speeds of up to 3,107 miles (5,000 kilometers) per second, but are much closer to the nucleus than the persistent wind,” said lead scientist Jelle Kaastra of the SRON Netherlands Institute for Space Research in a statement. “The new gas outflow blocks 90 percent 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.”
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The last observation of this galaxy was from the Hubble telescope in 2011, but this time around scientists combined data from NASA’s Swift spacecraft, the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Chandra X-ray Observatory, along with the European Space Agency’s (ESA) X-ray Multi-Mirror Mission (XMM-Newton) and Integral gamma-ray observatory (INTEGRAL) to get a fuller picture of what the black hole was doing.
First direct evidence that winds are accelerated by shielding x-ray radiation
Scientists had thought that in order for the gas streams coming out of a black hole to be accelerated to high speeds there should be some process that shields them from X-rays, but this is the first time that they have found direct evidence of that actually happening. These findings can help scientists understand how supermassive black holes interact with galaxies and how they can regulate each others’ growth.
“I saw signatures of much colder gas than was present before, indicating that the wind had cooled down due to a significant decrease in X-ray radiation from the galaxy’s nucleus,” said Gerard Kriss of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. “This is the first time we’ve seen a stream like this move into our line of sight. We got lucky.”