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Starts With A Bang

The Early Universe’s Most Massive Galaxy Cluster Revealed

From 10 billion years ago, a cluster more than 500 trillion times the Sun’s mass is revealed to us.

“If you take a galaxy and try to make it bigger, it becomes a cluster of galaxies, not a galaxy. If you try to make it smaller than that, it seems to blow itself apart.” –Jeremiah P. Ostriker

13.8 billion years ago, the Universe as we know it came into existence. Filled with matter and radiation, it would cool, clump together and eventually form stars, galaxies, and large-scale structure under the influence of gravitation.

The big requirement is time; moving trillions of suns’ worth of mass takes time. After billions of years, only a handful of galaxy clusters will be among the most massive. But as we look farther away, and hence earlier and earlier, we expect smaller, lower-mass clusters. Yet 16 billion light years away, IDCS J1426.5+3508, with a mass of 500 trillion suns, has already emerged.

Image credit: M. Brodwin et al., 2016, Ap.J. (in press), via

Despite the fact that the Universe was only 3.76 billion years old at the time — barely a quarter of its present age — this cluster already has nearly 20% the mass of the heaviest cluster of all: El Gordo.

The El Gordo galaxy cluster, imaged by the Hubble Space Telescope and with the dark matter mapped out. Image credit: NASA, ESA, J. Jee (University of California, Riverside, USA).

It’s the only cluster this distant with masses from three independent techniques: gravitational lensing, X-ray gas, and internal dynamics.

This image reveals the gravitational lensing mass of this cluster, with the lensed background galaxy shown inset. Image credit: NASA/ESA/University of Florida, Gainsville/University of Missouri-Kansas City/UC Davis.

Discovered by Spitzer, it was rediscovered in archival Chandra data, and then reimaged for 28 hours.

Astronomers have made the most detailed study yet of an extremely massive young galaxy cluster using three of NASA’s Great Observatories. This multi-wavelength image shows this galaxy cluster, IDCS 1426.5+3508, in X-rays from Chandra (blue), visible light from Hubble (green), and infrared light from Spitzer (red). This rare galaxy cluster weighs almost 500 trillion Suns and it was observed when the Universe was less than a third of its current age. It is the most massive galaxy cluster detected at such an early epoch, and, thus, has important implications for understanding how these mega-structures formed and evolved in the young Universe.

Also captured by Hubble, this cluster may, by today, be the most massive one in the visible Universe.

A Hubble space telescope image of galaxy cluster IDCS J1426.5+3508. Image credit: NASA, ESA, and M. Brodwin (University of Missouri).

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.

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