COMING EVENTS

PUBLIC OBSERVING Prairie Park Nature Center

SUNDAY December 12 8:00—9:30 PM

MONTHLY MEETING

Friday, Dec. 10, 2010 2001 Malott Hall

L.S.S.T Dr. Barbara Anthony–Twarog

President:

Rick Heschmeyer rcjbm@sbcglobal.net University Advisor:

Dr. Bruce Twarog btwarog@ku.edu

Webmaster: Gary Webber

gwebber@ku.edu Observing Clubs

Doug Fay dfay@ku.edu

Report from the Officers: The annual Webelo education evening went off without a hitch, providing a few hundred young scouts and par-ents with an opportunity to learn some basic astronomy and see the sky through a telescope, many for the first time. A loud and sincere thank you to all those who helped at the event, both inside and out, especially Rick Heschmeyer for taking on this task every year. Unfortunately, our monthly Sunday observing session wasn’t quite as lucky. After scattered clouds all day, at ~7:30 PM it clouded up completely and a quick deci-sion was made to cancel. We have one more session

this year on Sunday Dec. 12, the same weekend as the meeting. Hopefully we will be blessed by some of the that crisp, clear, cold evening air that eve-ryone loves in December. Brrrrrrrrrr!

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Volume 36 Number 12 December 2010

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INSIDE THIS ISSUE

Galactic Train Wreck 2

Intergalactic Sandbars 3

NASA Space Place 4

DEC. MEETING POSTER 5

HST: Dark Matter Map 6

Sandbars (continued) 7

Fermi (continued) 7

WISE: Star in Flames 8

Fermi Finds Structure 9

Dark Matter (continued) 10

Train Wreck (continued) 7

About the Astronomy Associates of Lawrence

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The club is open to all people interested in sharing their love for astronomy. Monthly meetings are typically on the second Fri-day of each month and often feature guest speakers, presentations by club members, and a chance to exchange amateur as-tronomy tips. Approximately the last Sunday of each month we have an open house at the Prairie Park Nature Center. Periodic

star parties are scheduled as well. For more information, please contact the club officers:our president, Rick Heschmeyer at rcjbm@sbcglobal.net, our webmaster, Gary Webber, at gwebber@ku.edu, or our faculty advisor, Prof. Bruce Twarog at

btwarog@ku.edu. Because of the flexibility of the schedule due to holidays and alternate events, it is always best to check the Web site for the exact Fridays and Sundays when events are scheduled. The information about AAL can be found at

http://www.ku.edu/~aal.

Copies of the Celestial Mechanic can also be found on the web at http://www.ku.edu/~aal/celestialmechanic

Our final meeting of the year in December will be our end-of-year holiday celebration, along with our usual selection of door prizes dominated by some fascinating reading on astronomy and space science. For our presentation, we will have a report on the next generation of ground-based astronomical technology, the Large Synoptic Survey Telescope (LSST), rescheduled from our October meeting. This 8m-class telescope is currently in the design and construction phase, with the mirror purchased and a site selected at Cerro Pachon in Chile. The telescope has been selected as the top priority for the astronomical community by the 2010 Astronomy Decadal Survey, which sets fund-ing/planning priorities for the community. There is no basketball scheduled for Dec. 10, so parking shouldn’t be a problem. Hope to see you at the meeting for some fun and refreshments. If you can’t make it, have a safe and won-derful holiday.

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Spitzer Reveals a Buried Explosion Sparked by a Galactic Train Wreck Spitzer Press Release

Astronomers using NASA's Spitzer Space Telescope have found a stunning burst of star formation that beams out as much infra-red light as an entire galaxy. The collision of two spiral galaxies has triggered this explosion, which is cloaked by dust that renders its stars nearly invisible in other wavelengths of light. The starburst newly revealed by Spitzer stands as the most luminous ever seen taking place away from the centers, or nuclei, of merging parent galaxies. It blazes ten times brighter than the nearby Uni-verse's previous most famous "off-nuclear starburst" that gleams in another galactic smashup known as the Antennae Galaxy. The new findings show that galaxy mergers can pack a real star-making wallop far from the respective galactic centers, where star-forming dust and gases typically pool.

"This discovery proves that merging galaxies can generate powerful starbursts outside of the centers of the parent galaxies," says Hanae Inami, first author of a paper detailing the results in the July issue of The Astronomical Journal. Inami is a graduate student at The Graduate University for Advanced Studies in Japan and the Spitzer Science Center at the California Institute of Technology. She adds: "The infrared light emission of the starburst dominates its host galaxy and rivals that of the most luminous galaxies we see that are relatively close to our home, the Milky Way." "No matter how you slice it, this starburst is one of the most luminous objects in the local Universe," agrees Lee Armus, second author of the paper and a senior research astronomer also at the Spitzer Science Center.

Inami, Armus and their colleagues spotted the buried starburst with Spitzer in the interacting galaxies known as II Zw 096. This galactic train wreck - located around 500 million light years away in the constellation Delphinus (the Dolphin) - will continue to un-fold for a few hundred million years. Gravitational forces have already dissolved the once-pinwheel shape of one of II Zw 096's pair of merging galaxies. The ultra-bright starburst region spans 700 light-years or so - just a tiny portion of II Zw 096, which streams across some 50,000 to 60,000 light-years - yet it blasts out 80 percent of the infrared light from this galactic tumult. Based on Spitzer data, researchers estimate the starburst is cranking out stars at the breakneck pace of around 100 solar masses, or masses of our Sun, per year. The prodigious energy output of this starburst in a decentralized location as revealed in the infrared has surprised the Spitzer researchers. The new observations go to show how the notion of a cosmic object's nature can change tremendously when viewed at different wavelengths of light. In this way, the shapes and dynamics of distant, harder-to-study ga-lactic mergers could turn out to be a good deal more complex than current observations over a narrow range of wavelengths imply.

"Most of the far-infrared emission in II Zw 096, and hence most of the power, is coming from a region that is not associated with the centers of the merging galaxies," Inami explains. "This suggests that the appearances and interactions of distant, early galax-ies during epochs when mergers were much more common than today in the Universe might be more complicated than we think."

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Astronomers Probe 'Sandbar' Between Islands of Galaxies Spitzer Press Release

Astronomers have caught sight of an unusual galaxy that has illuminated new details about a celestial "sandbar" con-necting two massive islands of galaxies. The research was conducted in part with NASA's Spitzer Space Telescope. These "sandbars," or filaments, are known to span vast distances between galaxy clusters and form a lattice-like struc-ture known as the cosmic web. Though immense, these filaments are difficult to see and study in detail. Two years ago, Spitzer's infrared eyes revealed that one such intergalactic filament containing star-forming galaxies ran between the galaxy clusters called Abell 1763 and Abell 1770.

Now these observations have been bolstered by the discovery, inside this same filament, of a galaxy that has a rare boomerang shape and unusual light emissions. Hot gas is sweeping the wandering galaxy into this shape as it passes through the filament, presenting a new way to gauge the filament's particle density. Researchers hope that other such galaxies with oddly curved profiles could serve as signposts for the faint threads, which in turn signify regions ripe for forming stars.

"These filaments are integral to the evolution of galaxy clusters -- among the biggest gravitationally bound objects in the universe -- as well as the creation of new generations of stars," said Louise Edwards, a postdoctoral researcher at the California Institute of Technology in Pasadena, and lead author of a study detailing the findings in the Dec. 1 issue of the Astrophysical Journal Letters. Her collaborators are Dario Fadda, also at Caltech, and Dave Frayer from the Na-tional Science Foundation's National Radio Astronomy Observatory, based in Charlottesville, Virginia.

Astronomers spotted the bent galaxy about 11 million light-years away from the center of the galaxy cluster Abell 1763 during follow-up observations with the WIYN Observatory near Tucson, Ariz., and radio-wave observations by the Very Large Array near Socorro, N.M. The WIYN Observatory is named after the consortium that owns and operates it, which includes the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observa-tories.The galaxy has an unusual ratio of radio to infrared light, as measured by the Very Large Array and Spitzer, mak-ing it stand out like a beacon. This is due in part to the galaxy having twin jets of material spewing in opposite directions

from a supermassive black hole at its center. These jets have puffed out into giant lobes of material that emit a tre-mendous amount of radio waves.

Edwards and her col-leagues noticed that these lobes appear to be bent back and away from the galaxy's trajec-tory through the fila-ment. This bow shape, the astronomers rea-soned, is due to parti-cles in the filament pushing on the gas and dust in the lobes. By measuring the angle of the arced lobes, Ed-wards' team calculated the pressure exerted by the filaments' particles and then determined the density of the me-dium. The method is somewhat like looking at streamers on a kite soaring overhead to

judge the wind strength and the thickness of the air. According to the data, the density inside this filament is indeed about 100 times the average density of the universe. This value agrees with that obtained in a previous X-ray study of filaments and also nicely matches predictions of supercomputer simulation.

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Blue Rings around Red Galaxies

by Trudy E. Bell and Dr. Tony Phillips

Beautiful flat rings around the planet Saturn are one thing—but flat rings around entire galaxies?

That is the astonishing discovery that two astronomers, Samir Salim of Indiana University at Bloomington and R. Michael Rich of UCLA described in the May 10, 2010, issue of The Astrophysical Journal Letters.

“For most of the twentieth century, astronomers observing at visible wavelengths saw that galaxies looked either ‘red and dead’ or ‘blue and new,’” explained Salim. Reddish galaxies were featureless, shaped mostly like balls or lentils; bluish ones were magnificent spirals or irregular galaxies. Elliptical galaxies looked red, astronomers reasoned, because they had mostly old red giant stars near the end of their life cycles, and little gas from which new stars could form. Spiral and irregular galaxies looked blue, however, because they were rich in gas and dust that were active nurseries birthing hot, massive, bluish stars.

At least, that's how galaxies appear in visible light.

As early as the 1970s, though, the first space-borne telescopes sensitive to ultraviolet radiation (UV) revealed something mysterious: a few red elliptical galaxies emitted “a surprising ultraviolet excess,” said Rich. The observations suggested that some old red galaxies might not be as “dead” as previously supposed.

To investigate, Salim and Rich used NASA’s Galaxy Evolution Explorer satellite to identify 30 red elliptical galaxies that also emitted the strongest UV. Then they captured a long, detailed picture of each galaxy using the Hubble Space Tele-scope. “Hubble revealed the answer,” says Salim. The UV radiation was emitted by enormous, flat bluish rings that com-pletely surrounded each reddish galaxy, reminiscent of the rings of Saturn. In some cases, the bluish rings even showed a faint spiral structure!

Because the bluish UV rings looked like star-forming spiral arms and lay mostly beyond the red stars at the centers of the elliptical galaxies “we concluded that the bluish rings must be made of hot young stars,” Salim continued. “But if new stars are still being formed, that means the red-and-dead galaxies must have ac-quired some new gas to make them.”

How does a galaxy “acquire some gas?” Salim speculates that it was an act of theft. Sometimes galaxies have close encounters. If a gas-rich irregular galaxy passed close to a gas-poor elliptical gal-axy, the gravity of the elliptical galaxy could steal some gas.

Further studies by Galaxy Evolution Ex-plorer, Hubble and other telescopes are expected to reveal more about the proc-ess. One thing is certain, says Rich: “The evolution of galaxies is even more surprising and beautiful than we imag-ined.”

The press release is available at http://www.galex.caltech.edu/newsroom/glx2010-03f.html. The full published article is “Star Formation Signatures in Optically Quiescent Early-Type Galaxies” by Samir Salim and R. Michael Rich, The Astrophysical Journal Letters 714: L290–L294, 2010 May 10. Point the kids to the Photon Pile-up Game at http://spaceplace.nasa.gov/en/kids/galex/photon, where they can have fun learning about the particle nature of light.

The Galaxy Evolution Explorer UV space telescope helped to identify red ellipti-cal galaxies that also emitted the strongest UV. These are detailed, long-exposure Hubble Space Telescope images of four of these galaxies that cap-ture the UV-emitting rings and arcs indicative of new star formation.

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Detailed Dark Matter Map Yields Clues to Galaxy Cluster Growth HST PRESS RELEASE

Astronomers using NASA's Hubble Space Telescope took advantage of a giant cosmic magnifying glass to create one of the sharpest and most detailed maps of dark matter in the universe. Dark matter is an invisible and unknown sub-stance that makes up the bulk of the universe's mass.

The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years. The result suggests that galaxy clusters may have formed earlier than expected, before the push of dark energy inhibited their growth. A mysterious property of space, dark energy fights against the gravitational pull of dark matter.

Dark energy pushes galaxies apart from one another by stretch-ing the space between them, thereby suppressing the formation of giant structures called galaxy clusters. One way astronomers can probe this primeval tug-of-war is through mapping the distribu-tion of dark matter in clusters.

A team led by Dan Coe at NASA's Jet Propulsion Laboratory in Pasadena, Calif., used Hubble's Advanced Camera for Surveys to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster's gravity, the majority of which comes from dark matter, acts like a cosmic magnifying glass, bending and amplifying the light from distant galaxies behind it. This effect, called gravitational lensing, pro-duces multiple, warped, and greatly magnified images of those galaxies, like the view in a fun-house mirror. By studying the distorted images, astronomers estimated the amount of dark matter within the cluster. If the cluster's gravity only came from the visible galaxies, the lensing distortions would be much weaker.

Based on their higher-resolution mass map, Coe and his collabora-tors confirm previous results showing that the core of Abell 1689 is much denser in dark mat-ter than expected for a cluster of its size, based on computer simu-lations of structure growth. Abell 1689 joins a handful of other well-studied clusters found to have similarly dense cores. The finding is surprising, because the push of dark energy early in the universe's history would have stunted the growth of all galaxy clusters.

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This NASA Hubble Space Telescope image shows the distribution of dark matter in the center of the giant galaxy cluster Abell 1689, containing about 1,000 galaxies and trillions of stars. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble cannot see the dark matter directly. Astrono-mers inferred its location by analyzing the effect of gravitational lensing, where light from galaxies behind Abell 1689 is distorted by intervening matter within the cluster.

Researchers used the observed positions of 135 lensed images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue, on an image of the cluster taken by Hubble's Advanced Camera for Surveys. If the cluster's gravity came only from the visible galaxies, the lensing distortions would be much weaker. The map reveals that the densest concentration of dark matter is in the cluster's core.

Abell 1689 resides 2.2 billion light-years from Earth. The image was taken in June 2002.

Galaxies tend to bunch together as great islands in the void of space, called galaxy clusters. These galaxy groupings themselves often keep company with other clusters in "superclusters" that loom as gargantuan, gravitationally associated walls of galaxies. These structures evolved from denser patches of material as the universe rapidly expanded after the Big Bang, some 13.7 billion years ago. The clumps and threads of this primordial matter eventually cooled, and some of it has condensed into the galaxies we see today. The leftover gas is strewn in filaments between galaxy clusters. Much of it is still quite hot -- about one million degrees Celsius (1.8 million degrees Fahrenheit) -- and blazes in high-energy X-rays that permeate galaxy clusters. Filaments are therefore best detected in X-ray light, and one direct density reading of the strands has previously been obtained in this band of frequencies.

But the X-ray-emitting gas in filaments is much more diffuse and weak than in clusters, just as submerged sandbars are extremely hard to spot at sea compared to islands poking above the water. Therefore, obtaining quality observations of filaments is time-consuming with current space observatories. The technique by Edwards and her colleagues, which uses radio frequencies that can reach a host of ground-based telescopes, points to an easier way to probe the interiors of gal-axy-cluster filaments. Instead of laboring to find subtle X-rays clues, astronomers could trust these arced "lighthouse" galaxies to indicate just where cosmic filaments lie. Knowing how much material these filaments contain and how they interact with galaxy clusters will be very important for understanding the overall evolution of the universe, Edwards said.

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Milky Way's black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way's cen-ter several million years ago. "In other galaxies, we see that starbursts can drive enormous gas outflows," said David Spergel, a scientist at Princeton University in New Jersey. "Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics." Hints of the bubbles appear in earlier spacecraft data. X-ray observations from the German-led Roentgen Satellite suggested subtle evidence for bubble edges close to the galactic center, or in the same orientation as the Milky Way. NASA's Wilkinson Microwave Anisotropy Probe detected an excess of radio signals at the position of the gamma-ray bubbles.

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In galaxy mergers, individ-ual stars rarely slam into one another because of the vast distances separating them; even in the compara-tively crowded central hubs of spiral galaxies, trillions of kilometers still often yawn between the stars. But giant, diffuse clouds of gas and dust in galaxies do crash together - passing through each other some-what like ocean waves - and in turn spur the gravita-tional collapse of dense pockets of matter into new stars. These young, hot stars shine intensely in the energetic ultraviolet part of the spectrum. In the case of II Zw 096, however, a

thick shroud of gas and dust still surrounds this stellar brood. The blanket of material absorbs the stars' light and re-radiates it in the lower-energy, infrared wavelengths that gleam clear through the dust to Spitzer's camera.

Astronomers were lucky to capture this transient phase in the evolution of the starburst and of the daughter galaxy that will eventually coalesce out of the collision. "Spitzer has allowed us to see the fireworks before all the gas and dust has cleared away, giving us a preview of the exciting new galaxy being built under the blanket," Inami says. Merging galaxies such as II Zw 096 also offer a sneak peek at the fate of our Milky Way in some 4.5 billion years when it is expected to plow into its nearest large galactic neighbor, the Andromeda Galaxy. Off-nuclear starbursts such as that in II Zw 096 and the Antennae Galaxy could occur in the vicinity of our Solar System, perhaps, which is located about two-thirds of the way out from the Milky Way's glowing, bulging center. "This kind of dramatic thing happening in II Zw 096 could happen to the Milky Way and Andromeda when they meet in the far future," says Inami.

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WISE Catches a Runaway Star in Flames At a time of year when many people travel long distances to be with their families for the holidays, NASA’s Wide-field Infrared Survey Explorer, or WISE, captured this view of a runaway star racing away from its original home. Seen here surrounded by a glowing cloud of gas and dust, the star AE Aurigae appears to be on fire. Ap-propriately, the cloud is called the Flaming Star Nebula. A runaway star is one that is hurled into high-speed motion through a supernovae explosion or collision with nearby stars. Like an angry teenager who storms out of the house after a family fight, runaway stars are ejected from their birthplace and race off to other parts of the Galaxy. The runaway star AE Aurigae was likely born in Trapezium Cluster, which is located in the constellation Orion. It formed a binary star system with the star Mu Columbae. Approximately 2.5 million years ago, these two stars col-lided with another binary star system in the Trapezium Cluster. This collision sent both AE Aurigae and Mu Colum-bae hurtling through space in opposite directions at a speed of 100 kilometers per second. Today, AE Aurigae can be seen in the constellation Auriga, while its former binary star Mu Columbae is located in the constellation Columba. The wind from AE Aurigae blows away electrons from the gas surrounding it. This ionized gas begins to emit light, creating what is known as an emission nebula. The star also heats up nearby dust, causing it to glow in infrared wavelengths. As seen in visible light, this dust reflects the light of nearby stars, so it is called a reflection nebula.

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NASA's Fermi Telescope Finds Giant Structure in our Galaxy NASA's Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way. The feature spans 50,000 light-years and may be the remnant of an eruption from a supersized black hole at the center of our galaxy. "What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center," said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who first recognized the feature. "We don't fully understand their nature or origin."

The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be millions of years old. A paper about the findings has been accepted for publication in The Astrophysical Journal. Finkbe-iner and his team discovered the bubbles by processing publicly available data from Fermi's Large Area Telescope (LAT). The LAT is the most sensitive and highest-resolution gamma-ray detector ever launched. Gamma rays are the highest-energy form of light. Other astronomers studying gamma rays hadn't detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light inter-act with light and interstellar gas in the Milky Way. The LAT team constantly refines models to uncover new gamma-ray sources obscured by this so-called diffuse emission. By using various estimates of the fog, Finkbeiner and his colleagues were able to isolate it from the LAT data and unveil the giant bubbles. Scientists now are conducting more analyses to better understand how the never-before-seen structure was formed. The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The struc-ture's shape and emissions suggest it was formed as a result of a large and relatively rapid energy release - the source of which remains a mystery. One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the

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From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years, or roughly half of the Milky Way's diameter, as shown in this illustration. Hints of the bubbles' edges were first observed in X-rays (blue) by ROSAT, a Ger-many-led mission operating in the 1990s. The gamma rays mapped by Fermi (magenta) extend much farther from the galaxy's plane. Credit: NASA's Goddard Space Flight Center

AAL Astronomy Associates of Lawrence

University of Kansas Malott Hall 1251 Wescoe Hall Dr, Room 1082 Lawrence, KS 66045-7582

Celestial Mechanic December 2010

"Galaxy clusters, therefore, would had to have started forming billions of years earlier in order to build up to the num-bers we see today," Coe explains. "At earlier times, the universe was smaller and more densely packed with dark matter. Abell 1689 appears to have been well fed at birth by the dense matter surrounding it in the early universe. The cluster has carried this bulk with it through its adult life to appear as we observe it today."

Abell 1689 is among the most powerful gravitational lensing clusters ever observed. Coe's observations, combined with previous studies, yielded 135 multiple images of 42 background galaxies.

"The lensed images are like a big puzzle," Coe says. "Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions." Coe used this information to produce a higher-resolution map of the cluster's dark matter distribution than was possible before.

Coe teamed with mathematician Edward Fuselier, who, at the time, was at the United States Military Academy at West Point, to devise a new technique to calculate the new map. "Thanks, in large part, to Eddie's contributions, we have finally `cracked the code' of gravitational lensing. Other methods are based on making a series of guesses as to what the mass map is, and then astronomers find the one that best fits the data. Using our method, we can obtain, directly from the data, a mass map that gives a perfect fit."

Astronomers are planning to study more clusters to confirm the possible influence of dark energy. A major Hubble program that will analyze dark matter in gigantic galaxy clusters is the Cluster Lensing and Supernova survey with Hubble (CLASH). In this survey, the telescope will study 25 clusters for a total of one month over the next three years. The CLASH clusters were selected because of their strong X-ray emission, indicating they contain large quan-tities of hot gas. This abundance means the clusters are extremely massive. By observing these clusters, astrono-mers will map the dark matter distributions and look for more conclusive evidence of early cluster formation, and pos-sibly early dark energy.

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