A new clue to an ancient cosmic mystery has emerged in the giant Shapley supercluster, which contains about 8,000 galaxies. Thanks to X-ray observations, scientists have discovered a colossal filament — a thread of superheated gas about 23 million light-years long. It stretches between four clusters of galaxies in this cosmic cluster. The discovery is described in a publication in Astronomy & Astrophysics.
“For the first time, our results closely match what we see in our leading model of the cosmos – something that’s not happened before. It seems that the simulations were right all along,” emphasizes the head of the study, astrophysicist Konstantinos Migkas from Leiden Observatory.
Mystery of missing matter
Most of the matter in the Universe is mysterious “dark matter.” Only about 15% is ordinary (baryonic) matter, which makes up stars, planets, gas, and ourselves. By studying the cosmic microwave background of the early Universe, scientists have calculated fairly accurately how much of this ordinary matter existed immediately after the Big Bang.
However, modern observations show that all visible ordinary matter — galaxies, stars, dust — accounts for only about half of that original amount. Where did the rest disappear to? A fundamental law of physics states that matter cannot simply cease to exist.
Cosmic web
The best explanation is that the missing matter is scattered in an incredibly thin layer across the vast spaces between galaxies — in a structure known as the cosmic web. This network of dark matter filaments serves as the framework of the Universe, along which galaxies move. It is believed that hot gas – ordinary matter – is trapped and dispersed in these filaments.
It is extremely difficult to find direct evidence of the existence of this gas in the filaments due to its extremely low density and weak radiation. But that is exactly what Migkas’ team managed to do.
The art of telescopes
The researchers used an ingenious approach, combining data from two X-ray telescopes: Suzaku and XMM-Newton. Scientists used Suzaku data on the space between galaxy clusters A3528S/N and A3530/32 to detect the glow of gas inside the filament. Then, using data from XMM-Newton, they carefully cleaned the signals of all bright point sources that could interfere. The result is a clear map of a giant gas filament.
The open structure is impressive in scale: it is 23 million light-years long, and the mass of gas in it is equivalent to the mass of ten Milky Way galaxies. The gas is heated to temperatures exceeding 10 million degrees Celsius.
Most importantly, the properties of this filament — its size, location, mass, and temperature — perfectly match the predictions of cosmological models describing the formation and structure of the Universe. Most importantly, the properties of this filament — its size, location, mass, and temperature — perfectly match the predictions of cosmological models describing the formation and structure of the Universe.
“This research is a great example of collaboration between telescopes, and creates a new benchmark for how to spot the light coming from the faint filaments of the cosmic web,” notes ESA astronomer Norbert Schartel.
This discovery is one of the most convincing pieces of evidence to date that the missing ordinary matter is indeed hidden in the sparse hot gas filling the filaments of the cosmic web. It seems that the key piece of the cosmic puzzle has finally found its place.
According to universetoday.com
