Galaxies are gravitationally bound, large-scale astrophysical systems composed primarily of dark matter, stars, stellar remnants, gas, and dust, often embedded in extended dark matter halos. They exhibit diverse morphologies, including spiral, elliptical, and irregular types, and span mass scales from roughly 10⁷ to over 10¹² solar masses. Their internal dynamics are governed by gravity and angular momentum distribution, with baryonic components organized into disks, bulges, and halos, and frequently hosting central supermassive black holes. Galaxies are fundamental units of cosmic structure formation, participating in hierarchical assembly, mergers, and interactions within larger environments such as groups, clusters, and filaments of the cosmic web.
If you look across space with a telescope, you'll see countless galaxies, most of which host large central black holes, billions of stars and their attendant planets. The universe teems with huge, spectacular objects, and ...
Astronomy
Dec 4, 2025
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An international team led by the University of Oxford has identified one of the largest rotating structures ever reported: a "razor-thin" string of galaxies embedded in a giant spinning cosmic filament, 140 million light-years ...
Astronomy
Dec 3, 2025
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Galaxies like our Milky Way grew through cascading mergers of smaller galaxies that began billions of years ago. The ancient progenitors of galaxies like ours were small galaxies similar to modern-day dwarf galaxies like ...
Astronomy
Dec 3, 2025
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Astronomers have long debated the role of galaxy mergers in powering active supermassive black holes. Now an unprecedented dataset of a million galaxies from the Euclid telescope provides evidence that mergers play a dominant ...
Astronomy
Dec 2, 2025
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Using ESA's XMM-Newton satellite, astronomers from Stanford University and elsewhere have conducted deep X-ray observations of a nearby galaxy known as NGC 3221. The new observational campaign detected a faint active galactic ...
A team of astronomers from the International Center for Radio Astronomy Research (ICRAR) has released new data from an extensive galaxy evolution survey that found a galaxy's "neighborhood" plays a major role in how it changes ...
Astronomy
Nov 25, 2025
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In the early 1930s, Swiss astronomer Fritz Zwicky observed galaxies in space moving faster than their mass should allow, prompting him to infer the presence of some invisible scaffolding—dark matter—holding the galaxies together. ...
Astronomy
Nov 25, 2025
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An expanding universe complicates this picture just a little bit, because the universe absolutely refuses to be straightforward. Objects are still emitting light, and that light takes time to travel from them over to here, ...
Astronomy
Nov 24, 2025
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The European Space Agency's Euclid mission—designed to map the geometry of the dark universe with unprecedented precision—continues to deliver its first scientific insights. The Euclid Consortium has published a fresh set ...
Astronomy
Nov 20, 2025
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Tracking down black holes at the center of dwarf galaxies has proven difficult. In part it is because they have a tendency to "wander" and are not located at the galaxy's center. There are plenty of galaxies that might contain ...
Astronomy
Nov 19, 2025
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