Dark matter: Theory vs. Observed

Cosmology

Hubble Images Reveal Dark Matter Problem

Astronomers studying Hubble Space Telescope images of massive galaxy clusters have uncovered a potential problem with dark matter.

The Great Square of Pegasus

Deep Sky

Deep-sky Dive Into the Great Square of Pegasus

We return to Pegasus, but this time with a telescope to find a grab-bag of overlooked deep-sky treasures.

local cosmic structure

Cosmology

Cosmic Void “Pushes” Milky Way

Astronomers have discovered a giant cosmic void that explains why our Local Group of galaxies is moving through the universe as fast as it is.

Galaxy cluster CL J1001+0220

Cosmology

A Galaxy Cluster Caught in Transition?

Astronomers have caught a galaxy cluster in the prime of its life — perhaps just before it transitions to retirement.

A Chandra/Hitomi view of Perseus Cluster

Cosmology

Doomed Hitomi Gazed at Galaxy Cluster

In its first — and final — month of flight, the Hitomi X-ray observatory measured the calm within the bubbling core of the Perseus Cluster.

Galaxies

Galaxy Cluster Spotted in Early Universe

Astronomers discover a vast collection of young galaxies from the early universe.

galaxy clusters and how clumped together they are

Cosmology

Dark Matter Makes Galaxy Clusters Clump

How much galaxy clusters huddle together depends in part on how fast these clusters formed — and that formation rate depends on dark matter.

Galaxy cluster Abell 2744

Galaxies

Ghostly Light From Dead Galaxies

Astronomers are peering into a galaxy cluster’s past, using Hubble’s Frontier Fields to measure the light from ghost stars cast adrift in galaxy collisions.

local supercluster

Galaxies

Laniakea: Our Home Supercluster

Astronomers have mapped the cosmic watershed and discovered a massive supercluster that extends more than 500 million light-years and contains 100,000 large galaxies. The Milky Way sits on the edge of this humongous structure.

Planck cosmic microwave background

Cosmology

Mystery of the Missing Galaxy Clusters

Astronomers have counted up the number of galaxy clusters in the cosmos and found a problem: the number is much lower than they expected. What's going on?

Cosmology

New Heavyweight Galaxy Cluster

Astronomers have discovered a supermassive galaxy cluster that both meets and challenges expectations for how clusters ought to behave.

Cosmology

Hubble Images Stir Up Dark Matter Debate

Dark matter in the "Train Wreck" galaxy cluster (Abell 520) appears to behave in unusual ways. Now, new Hubble images are heating up the debate.

Galaxies

The Most Distant Galaxy Cluster

Many instruments working together have profiled a baby galaxy group, seen not long after the Big Bang, of the kind that probably evolved into our Milky Way.

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