Just before its untimely death in March, the Hitomi satellite was able to collect X-ray data from the Perseus galaxy cluster, allowing scientists to track the motion of emissions from this part of the universe for the first time and find that this movement is less turbulent than expected.
According to BBC News, the data, which was published in Wednesday’s edition of the journal Nature, indicates that the hot gases located between galaxies in the Perseus cluster travel at a far slower speed (340,000 mph / 540,000 km/h) and in a steadier way than previously thought.
“For the first time, we have mapped the motion of the X-ray-emitting gas in a cluster of galaxies and determined its velocity structure over a wide range of spatial scales,” Richard Kelley, the US principal investigator for the Hitomi collaboration and a researcher at the NASA Goddard Space Flight Center in Greenbelt, Maryland, said in a statement.
He added that while the gas in this cluster, which is located roughly 240 million light years from Earth, “is continually stirred by fast outflows from the central black hole,” that “its velocities are small on astronomical scales and show evidence for only minor levels of turbulence.”
The Hitomi satellite was originally named Astro-H, but was renamed once in orbit.
Discoveries made possible due to Hitomi’s cutting-edge spectrometer
Hitomi, a satellite whose key components were built at Goddard, launched in February but soon began to spiral out of control. By the end of the next month, scientists on the ground lost contact with the $250,000 probe, but with these observations, it has provided a final, parting gift.
Hot gases in the Perseus cluster can reach average temperatures of 90 million degrees Fahrenheit (50 million degrees Celsius) and glow brightly when viewed in X-rays, NASA explained. Before Hitomi, however, astronomers lacked the capability to accurate measure the detailed dynamics of these gases, largely due to gas bubbles expelled by a nearby, active supermassive black hole.
Image of the Perseus cluster taken by the satellite before it went offline. (Credit: JAXA, NASA, ESA)
Using its Soft X-ray Spectrometer (SXS), Hitomi monitored a region in the core of the cluster for more than 2 1/2 days, and the resulting X-ray spectrum revealed emission lines from a number of metals (such as iron, nickel, chromium, and manganese) in data that were 30 times more detailed than the best previous observations. Those metals, the US space agency explained, formed in the billions of massive stars in the cluster and dispersed after those stars went supernova.
The velocity of the gases were said to be modest by cosmic standards, and experts expected them to be extremely chaotic. However, as Brian McNamara, a research team member and a professor of physics and astronomy at the University of Waterloo in Canada, told BBC News, they learned that the gas was “relatively stable” and was getting “pushed around” less than they expected.
“This is the first time we’ve looked at a galaxy cluster with an instrument capable of resolving the components of various atomic emission lines, and we immediately saw contradictions with current models,” added his colleague, Maxim Markevitch from Goddard. “This is a long-awaited tool for diagnosing the conditions in cosmic plasmas that we can finally apply to galaxy clusters, and there will be a number of papers to come based on these data.”
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Image credit: Jay Gabany
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