Galaxy Cluster Abell 2029 Had Violent Past, Chandra Reveals – Sci.News

NASA’s Chandra X-ray Observatory has uncovered evidence of an ancient, violent cosmic collision within the galaxy cluster Abell 2029, challenging the long-held perception of the cluster as one of the most stable structures in the known universe.

Abell 2029 has frequently been described by astronomers as the most relaxed cluster in the Universe because of the apparent calm and undisturbed nature of the superheated gas that fills the space between its galaxies. However, new deep X-ray observations reveal that this current state of equilibrium is the result of a long recovery process following a massive gravitational event.

The findings, detailed in a study led by astronomers from Boston University and the Center for Astrophysics | Harvard & Smithsonian and published in the Astrophysical Journal, indicate that Abell 2029 is still settling down after a raucous collision with a smaller galaxy cluster that occurred approximately four billion years ago.

The research team, led by Courtney Watson, utilized the Chandra X-ray Observatory to obtain the deepest X-ray observation ever conducted of the cluster. Abell 2029 is located roughly one billion light-years from Earth in the constellation of Virgo.

The most striking evidence of the cluster’s chaotic history is the presence of a massive, nautilus-like spiral of superheated gas. This sloshing spiral extends approximately two million light-years from the center of the cluster, making it one of the longest structures of its kind ever observed.

According to the researchers, this spiral formation occurred when the gravitational effects of the collision caused the hot gas within the cluster to slosh to the side.

The team compared the movement of the gas to the way wine moves in a wine glass when the glass is disturbed.

Beyond the spiral, the Chandra data provided other indicators of the ancient impact, including evidence of a wide splash of cooler gas created during the collision. The researchers noted that these multiple pieces of evidence had never been seen together in a single cluster previously, allowing them to reconstruct the collision history with a level of detail that was previously unattainable.

To understand the significance of these findings, it is necessary to consider the composition of galaxy clusters. As the largest structures in the universe held together by gravity, these clusters consist of hundreds or thousands of galaxies, significant amounts of unseen dark matter, and vast quantities of gas that fill the voids between galaxies.

This intergalactic gas is typically heated to millions of degrees. At such extreme temperatures, the gas glows in X-ray light, which allows observatories like Chandra to map the distribution and movement of matter that would be invisible to optical telescopes.

The depth of the Chandra observations was critical in identifying these features. While the cluster appears relaxed in shallower images, the increased sensitivity of the deep observation revealed the subtle, large-scale patterns of the sloshing gas and the cooler splashes that betray its violent past.

The study highlights the dynamic nature of the universe, where even the most seemingly dormant structures may have undergone extreme transformations. The ability to trace these events billions of years after they occurred provides astronomers with a clearer understanding of how the largest structures in the cosmos evolve over time through mergers and collisions.

The combined data from Chandra’s X-ray imagery and optical light from stars and galaxies, provided by the Pan-STARRS telescope in Hawaii, allowed the team to create a composite view of the cluster. This multi-wavelength approach confirmed that the spiral shape was a property of the hot gas rather than the distribution of the galaxies themselves.

By analyzing the scale and shape of the gas spiral, the research team can better estimate the mass of the colliding cluster and the dynamics of the encounter that began four billion years ago, contributing to the broader study of cosmic evolution and the role of dark matter in shaping galaxy clusters.