Galaxies | Astronomy.com

Unveiling the Andromeda Galaxy’s true nature

Alison Klesman — Fri, 10 Oct 2025 15:00:00 +0000

Over the course of human history, perhaps no single object in the night sky has drawn more attention than the Andromeda Galaxy, which the 10th-century Persian astronomer Abd al-Rahman al-Sufi dubbed a “nebulous smear.” For centuries, the fuzzy object nestled in the night sky between her mythological parents, Cepheus and Cassiopeia, and winged Pegasus heldContinue reading "Unveiling the Andromeda Galaxy’s true nature"

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Do dwarf galaxies have a large black hole in the center?

Astronomy Staff — Mon, 08 Sep 2025 13:00:00 +0000

Do dwarf galaxies have a large black hole in the center? Duane MorsePhoenix, Arizona Nearly all massive galaxies are known to host central black holes. And dwarf galaxies can indeed also host central black holes, but whether all or only a fraction of them do remains an open question in astronomy. Until recently, astronomers hadContinue reading "Do dwarf galaxies have a large black hole in the center?"

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The Milky Way’s faintest dwarf galaxy might actually be a star cluster

Michael E. Bakich — Wed, 20 Aug 2025 15:16:04 +0000

Ursa Major III orbits the Milky Way at a distance of 32,600 light-years. Until now, it was considered a dwarf spheroidal galaxy. Normally such a faint object wouldn’t be classified as such, but astronomers did so because of its large mass, which they assumed contains a lot of invisible dark matter. Recently, however, an internationalContinue reading "The Milky Way’s faintest dwarf galaxy might actually be a star cluster"

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JWST’s view of the Phoenix Cluster sparks scientific conundrum

Richard Talcott — Wed, 20 Aug 2025 15:00:00 +0000

Scientists have a good idea how stars should form in the central galaxies of rich clusters. The hot gas surrounding a cluster’s dominant innermost galaxy cools rapidly, sparking furious star formation. The problem: No one had found evidence for this cooling gas, and most central galaxies don’t create many stars. Astronomers suspect the solution toContinue reading "JWST’s view of the Phoenix Cluster sparks scientific conundrum"

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How did Edwin Hubble prove Andromeda was a galaxy?

Astronomy Staff — Mon, 07 Jul 2025 13:00:00 +0000

How did a Cepheid variable star help Edwin Hubble prove the Andromeda Nebula was a galaxy? Roger BradySan Quentin, California Cepheids are rare variable stars with periods ranging from about 1 to 120 days. Their light curve — a chart showing brightness over time — is characterized by rapid brightening followed by slow dimming inContinue reading "How did Edwin Hubble prove Andromeda was a galaxy?"

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How weird is the Milky Way?

Alison Klesman — Fri, 04 Jul 2025 13:00:00 +0000

In the vast expanse of the universe, the Milky Way Galaxy holds a special place in our hearts. It is our home, and after studying it for decades from our cosmic residence nestled within one of its majestic spiral arms, we know it better than any other galaxy. But how truly typical — or extraordinary —Continue reading "How weird is the Milky Way?"

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Hubble spots a cosmic bullseye

Richard Talcott — Thu, 12 Jun 2025 17:00:00 +0000

Sometimes even scientists get lucky. Yale University astronomer Imad Pasha was scanning some ground-based images when he stumbled across a galaxy boasting several rings. Because the object’s name, LEDA 1313424, doesn’t roll off the tongue, his team nicknamed it the Bullseye. This Hubble image reveals why it’s an apt moniker: The galaxy boasts nine rings,Continue reading "Hubble spots a cosmic bullseye"

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Galaxy cluster pileup sets record for the size of its glow

Mark Zastrow — Wed, 11 Jun 2025 01:39:33 +0000

When galaxies run into each other, they often appear to merge gracefully, their cores pirouetting around one another, drawn by their mutual gravitational attraction as their spiral arms extend outward in repose and their disks dissolve into an eternal embrace. But not in galaxy cluster PLCKG 287.0+32.9. Like a high-speed multi-car pileup in a HollywoodContinue reading "Galaxy cluster pileup sets record for the size of its glow"

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JWST gazes into the distant past through gravitational lens

Brooks Mendenhall — Mon, 02 Jun 2025 20:25:29 +0000

The James Webb Space Telescope (JWST) has captured a breathtaking new deep field image of the galaxy cluster Abell S1063, surpassing Hubble’s previous view in both depth and detail. Abell S1063, located 4.5 billion light-years away in the constellation Grus the Crane, acts as a gravitational lens. This massive cluster bends and focuses the lightContinue reading "JWST gazes into the distant past through gravitational lens"

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Astronomers have discovered the Big Wheel — here’s why it’s significant

Daniela Mata — Wed, 14 May 2025 17:13:13 +0000

Deep observations from the James Webb Space Telescope (JWST) have revealed an exceptionally large galaxy in the early universe. It’s a cosmic giant whose light has travelled over 12 billion years to reach us. We’ve dubbed it the Big Wheel, with our findings published March 17 in Nature Astronomy. This giant disk galaxy existed withinContinue reading "Astronomers have discovered the Big Wheel — here’s why it’s significant"

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