The Perseus signal is one of the most mysterious findings in the history of astronomy. A group of researchers gathered to explore the Perseus Cluster, a conglomeration of galaxies located a staggering 250 million light years from our solar system.
“I couldn’t believe my eyes,” said Esra Bulbul of the Harvard Center for Astrophysics in July of 2014.
The Perseus cluster is one of the most massive objects known in the universe. According to researchers, the cluster itself is wrapped by a humongous ‘atmosphere’ made up of plasma. However, the mystery does not end there.
“The cluster’s atmosphere is full of ions such as Fe XXV, Si XIV, and S XV. Each one produces a ‘bump’ or ‘line’ in the x-ray spectrum, which we can map using Chandra,” Bulbul explains. “These spectral lines are at well-known x-ray energies.” Yet, in 2012 when Bulbul added together 17 day’s worth of Chandra data, a new line popped up where no line should be. “A line appeared at 3.56 keV (kilo-electron volts) which does not correspond to any known atomic transition,” she said. “It was a great surprise.”
Bulbul and her colleagues were fascinated and couldn’t believe it at first.
Speaking about the Perseus cluster, Bulbul said: “It took a long time to convince myself that this line is neither a detector artifact nor a known atomic line.”
“I have done very careful checks. I have re-analyzed the data; split the data set into different subgroups, and verified the data from four other detectors on board two separate observatories. None of these efforts made the line disappear.”
Everything pointed towards the discovery being reliable. This was further confirmed when Bulbul and her colleagues discovered a nearly identical spectral signature in X-Ray emission originating from 73 other galaxy-clusters. The information was picked up by Europe’s XMM-Newton, an independent X-Ray telescope.
Shortly after Bulbul and her colleagues posted the study online, a group of scientists led by Alexey Boyarsky of Leiden University in the Netherlands presented evidence of the same spectral line in observations of the Andromeda galaxy, made by the XMM-Newton X-Ray telescope.
In short, the spectral line spotted by scientists is not originating from any KNOWN type of matter which ultimately lifts suspicions that it may have been caused by dark matter.
“After we submitted the paper theoreticians came up with about 60 different dark matter types which could explain this line. Some particle physicists have jokingly called this particle a ‘bulbulon’,” she laughed.
Further observations and studies will surely need to be performed in the future in order to understand one of the many mysteries of our universe.
To get to the bottom of this, the Japanese space agency launched an advanced X-ray telescope called “Astro-H.” Which might help astronomers in their hunt for answers?