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By a new image of a gigantic universe cluster of older x-ray data, scientists from the European Space Agency (ESA) have shown how the galaxies in the cluster are filled with huge amounts of gas, which can reach scorching temperatures of up to 100 million degrees Celsius (180 million degrees Fahrenheit).
The galaxy cluster Abell 2390 was recently pictured by ESA’s Euclid Missiondesigned for studying dark matter And dark energy by sounding out gravitational lensing occur in galaxy clusters. Because these clusters contain so much mass — up to ten trillion solar masses worth — they are able to absorb the substance of room–time around them, distorting it so much that light from distant galaxies in the background is greatly magnified. It is as if you are looking at it through a giant magnifying lens. Zooming in on the core of Abell 2390, we see that the lensing effect is most pronounced, with light from other galaxies billions of light-years away being stretched, distorted and amplified.
However, most of the mass of a cluster of galaxies is not contained within the galaxies themselves. In fact, they contribute barely 5% of the total mass of the cluster. The largest contributors are the hot intracluster gas between the galaxies in the cluster, which makes up about 15% of the cluster mass, and unseen dark matter, which makes up a whopping 80% of the mass of Abell 2390.
Although we can infer the presence of dark matter from the amount of gravitational lensing, we can’t see it. We can see the intracluster gas, however, thanks to the X-ray vision of ESA’s XMM-Newton mission, which discovered this gas in Abell 2390 in 2001.
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In this new composite view we see Euclid’s image of Abell 2390, which is 2.7 billion light-years away in the direction of the constellation Pegasusthe winged horse. Euclid’s image is incredible; it is a very wide field of view, the field of view through his 1.2-meter (3.9-foot) telescope is 1.25 by 0.73 square degrees. The image contains about 50,000 galaxies, many of which are not in Abell 2390, which is visible in the center of the image and itself contains thousands of galaxies. The most distant background galaxies, even far beyond Abell 2390, appear red because their light redshifted because of the expansion of the universeA handful of foreground stars are also visible, marked by their six-pointed diffraction peaks.
Superimposed on Euclid’s visible-light image is XMM-Newton’s detection of X-ray emission from the cluster. This is produced by ionized hydrogen gas at temperatures between 10 million and 100 million degrees Celsius (18 million to 180 million degrees F). At such temperatures, the gas emits only X-rays, so what we see here as the blue glow is a false-color representation of the X-ray signal. The X-ray emission is brightest toward the center of the cluster, where the intracluster gas is hottest and most concentrated.
Right in the heart of Abell 2390, amidst all this blazing gas, is what’s known as the brightest cluster galaxy, or BCG. Every major cluster of galaxies has one of these — in the nearby Virgo Cluster, the BCG is Messier 87. In other words, the BCG is a giant elliptical galaxy with an active supermassive black hole at the core there is feedback that – in the form of radiation streams – can heat the gas in the cluster and even prevent star formation in the other galaxies of the cluster.
In results published earlier this yearobservations of Abell 2390’s BCG with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile revealed a gigantic plume of molecular gas worth more than 10 billion solar masses, stretching across nearly 50,000 light years away from the BCG. Scientists think the plume may be the result of a gravitational disturbance caused by another galaxy passing close to the BCG or even merging with it in the crowded environment of Abell 2390. The disturbance caused by such an event could be enough to detach or separate the BCG and its surrounding dark matter halo from the intra-cluster gas, leaving a trail of molecular gas like that found in the plume by ALMA.
Meanwhile, the Low Frequency Array (LOFAR) in Europe has found several lobes of radio-emitting particles around the BCG of Abell 2390 at radio wavelengths. These lobes were produced by an intermittent but powerful beam emitted from the active black hole in the center of the BCG. The lobes are of different ages and point in different directions, implying that the jet—and thus the orientation of the black hole and the surrounding accretion disk of gas that feeds the jet—is precessing. In other words, it wobbles in a regular way, with the jet describing a circle above the rotation axis of the black hole.
The jets can heat the surrounding intra-cluster medium, but at present they appear to be in a dormant phase, with the hot X-ray emitting gas slowly cooling and falling back onto the BCG and other galaxies in the cluster, where the cooling gas may be forming new stars.
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A new innovation of Euclid is the ability to detect the faint stellar glow of billions of stars that have been torn from their galaxies by gravitational tidal forces in the turbulent environment of the cluster. Individually, the stars are far too faint to be seen at such great distances, but collectively they contribute an eerie glow, which is amplified in the Euclid image. By tracking where these anomalous intergalactic stars are converging, attracted by gravityastronomers can figure out where the dark matter is in Abell 2390.
The first images of Euclid’s universe, including one of Abell 2390, were released in May. The spacecraft, which launched in July 2023, has now begun a six-year mission to map the dark universe by observing billions of galaxies and galaxy clusters spanning 10 billion years of cosmic history.