New observations from NASA's Chandra X-ray Observatory and other telescopes capture a rare cosmic event: Two Galaxy clusters have collided and are now expected to turn back and slide to each other.

Galaxy clusters are some of the largest structures in the universe. They are bound by gravity and are monster-sized collections of hundreds or thousands of individual galaxies, massive amounts of superheated gas and invisible dark matter.

Galaxy cluster PSZ2 G181.06+48.47 (PSZ2 G181 for short) is about 2.8 billion light years away from the earth. Previously, radio observations of low-frequency arrays (Lofar) in the Netherlands were observed in the bracket-shaped structure of spots outside the system. In this new composite image, X-rays from Chandra (Purple) and ESA’s XMM-Newton (blue) have been used in conjunction with optical images of the stars in Lofar Data (red) and the field of view.

These structures may be shock fronts – similar to those produced by jets that break the sound barrier, which could be due to the initial collision interruption about a billion years ago. They have been driving out since the collision, and are currently about 11 million light-years away, the largest separation of these structures astronomers have ever seen.

Now, data from Chandra of NASA and XMM-Newton of ESA provide evidence that the PSZ2 G181 is expected to collide again. The first time through the collision between each other, the two clusters slowed down and began to crash towards the second.

Astronomers conducted detailed research on the X-ray observations at the collision site and discovered three impact fronts. These are consistent with the axis of the collision, which researchers believe are early signs of a second crash.

Researchers are still trying to determine how much mass each collision cluster contains. In any case, the total mass of the system is less than the other mass of a galaxy cluster collision. This makes the PSZ2 G181 anomaly a rare case for lower mass systems that collide galaxy clusters.

A paper describing these results appears in the recent Journal of Astrophysics (APJ), led by Andra Streo of the Center for Astrophysics | Harvard and Smithsonian (CFA) and collaborators. It is part of the three paper series in APJ. The second paper was led by Kamlesh Rajpurohit of CFA and the third paper was led by Eunmo Ahn of Yonsei University in the Republic of Korea.

The Chandra program is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama. The Chandra X-ray Center of the Smithsonian Observatory controls scientific operations in Cambridge, Massachusetts, and flight operations in Burlington, Massachusetts.

Learn more about Chandra X-ray Observatory and its mission here:

Visual description

In this version, a composite image illustrates a dramatic cosmic story that shows 2.8 billion light years from Earth. The image is presented with and without labels, detailing the consequences of two galaxy clusters colliding.

The center of the image is a cluster of collision galaxies, collectively known as PSZ2 G181. The clusters of this combination are somewhat similar to irregular violet peanut shells, with ribbon-shaped ends connected to the conical middle. There are several luminous spots inside the end of each bulb. Some galaxies in the cluster. The shape of the purple peanut is slightly tilted, surrounded by a blue haze of X-ray gas.

Away from the end of the bulb, at our upper left and lower right, are two spots, thick red lines. These could be shock fronts, similar to those created by jets that break the sound barrier. These combined galaxy clusters encapsulated by the initial collision about a billion years ago. They are currently 11 million light-years respectively.

New data from Chandra and XMM-Newton observations suggest that the PSZ2 G181 is expected to prepare for another powerful cosmic event. It has been sliding against each other, and two clusters are again in the collision process.

Megan Watzke
Chandra X-ray Center
Cambridge, Massachusetts.
617-496-7998
mwatzke@cfa.harvard.edu

Lane figueroa
Marshall Space Flight Center in Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov