Chuck Bednar for redOrbit.com – Your Universe Online
New observations of the Perseus and Virgo galaxy clusters made using NASA’s Chandra X-ray Observatory suggest that turbulence may be the reason that hot gas there has been unable to cool, providing a possible answer to a long-standing question as to why these galaxy clusters never seem to form large numbers of stars.
Clusters like Perseus and Virgo are the largest objects in the universe, containing hundreds of thousands of individual galaxies that are held together by gravity and immersed in gas reaching temperatures of several million degrees, according to the US space agency. Except for dark matter, this hot gas is the heftiest component of galaxy clusters and glows brightly in X-ray light detected by Chandra, a space telescope which launched in 1999.
Over time, the gas in the centers of these clusters should cool enough to lead to a tremendous amount of star formation, but astronomers have found that this is not the case in many galaxy clusters. They knew that the gas was being prevented from cooling and forming stars for some reason, but they did not understand exactly why.
Now, however, a team of researchers led by Irina Zhuravleva of Stanford University Kavli Institute for Particle Astrophysics and Cosmology in California report that they have found evidence that the heat is being channeled from turbulent motions identified by signatures detected in the X-ray images. They report their findings in the latest online edition of the journal Nature.
Previous research showed that supermassive black holes located in the center of large galaxies in the middle of these clusters emit tremendous amounts of energy around them in powerful jets of highly-energetic particles that cause cavities to develop in the hot gas, according to NASA.
The new study has found how energy can be transferred from those cavities to the surrounding gas, which could generate turbulence that disperses the gas and causes it to remain hot for up to billions of years. The evidence was found in Chandra data obtained from extended observations of Perseus and Virgo. During those observations, the team was able to measure fluctuations in the density of the gas and estimate the amount of turbulence in the gas.
“Any gas motions from the turbulence will eventually decay, releasing their energy to the gas,” explained co-author Eugene Churazov of the Max Planck Institute for Astrophysics in Munich, Germany. “But the gas won’t cool if turbulence is strong enough and generated often enough.”
“Our work gives us an estimate of how much turbulence is generated in these clusters,” added Alexander Schekochihin of the University of Oxford’s Rudolf Peierls Centre for Theoretical Physics in the UK. “From what we’ve determined so far, there’s enough turbulence to balance the cooling of the gas.”
The team’s findings support the so-called feedback model involving supermassive black holes in the centers of galaxy clusters, NASA said. While mergers between a pair of galaxy cluster also produce turbulence, the authors believe that outbursts from supermassive black holes are the primary source of this phenomenon in most clusters.
Related Links:
> Chandra X-ray Observatory – Observatories Reference Library
> What Is Dark Matter? – Podcast Interview With Dr. Matthew Walker
> Read the original NASA statement here
> Keep an eye on the cosmos with Telescopes
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Chandra Data Helps Solve The Puzzle Of Why Galaxy Clusters Contain So Few Stars
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