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A vast “island universe” of stars, gas, and dust. The universe may contain 100 billion or more galaxies. Galactic size and structure range from dwarfs and irregulars with no discernible structure and only a few million stars to giant spirals and ellipticals that span 100,000 light-years or more and contain hundreds of billions of stars. Galaxies clump together in web-like structures. Despite its great luminosity, most of a galaxy’s mass consists of dark matter, which produces no detectable energy.


Galaxies Fade May 21, 2010

Types of Galaxies May 21, 2010

Radio Programs

M82 A gas crisis for a vigorous galaxy March 26, 2017

Active Galaxies “Activating” the heart of a galaxy March 14, 2017

Barred Spirals Stepping up to the galactic bar December 18, 2016

Dark Matters Lighting up the darkness December 16, 2016

Brightest Galaxy The distant glow of a brilliant galaxy October 1, 2016

Sunflower Galaxy Sculpting a galactic sunflower August 26, 2016

Scutum Arm Wrapping an arm around the galaxy July 25, 2016

Moon and Spica An act of galactic cannibalism July 11, 2016

Grand M81 A “grand design” for a galaxy May 24, 2016

Super Spirals Making beautiful giant galaxies April 2, 2016

Hydra I A faint companion to the Milky Way April 1, 2016

Lacy Galaxies Finding big but hazy galaxies March 31, 2016

Evaporating Galaxy A galaxy that’s ripping itself apart March 23, 2016

Black Hole Snowplow Snowplowing lanes around a black hole March 4, 2016

Galactoseismology Ripples from a “galaxy quake” March 2, 2016

Triangulum Galaxy A busy member of the Local Group October 5, 2015

Andromeda Galaxy Taking in all of a giant galaxy September 15, 2015

Hercules Cluster Stirring up a cluster of galaxies May 13, 2015

On the Frontier Pushing the intergalactic frontier March 8, 2015

Spiral Galaxies Pinwheels and whirlpools February 15, 2015

Filling the Void Filling the intergalactic void January 18, 2015

Tadpole Galaxies The inside-out heads of tadpole galaxies November 27, 2014

Great Wall A wall of galaxies across the universe November 16, 2014

Maffei 1 A bright galaxy hides behind a veil of dust October 3, 2014

Powerful Jets Powerful jets from massive black holes August 11, 2014

Magellanic Clouds A new view of two close neighbors July 13, 2014

Leo T A tiny galaxy with bright ambitions May 24, 2014

Supernova Factory A galaxy with a steady supply of fireworks March 24, 2014

Condor Galaxy The condor stretches its galactic wings March 14, 2014

Triangulum Galaxy A galaxy that’s losing its identity November 9, 2013

Andromeda Galaxy III Building a galactic giant November 8, 2013

Galactic Thief A case of galactic thievery June 14, 2013

M101 A beautiful galactic neighbor May 30, 2013

GALEX Keeping an eye on the galactic action April 27, 2013

Coma Galaxy Cluster A brilliant cluster of galaxies April 18, 2013

Quasars II Lighting up a distant galaxy February 5, 2013

IC 10 A faint but busy galactic neighbor October 7, 2012

BL Lacertae A star that’s more than a star September 13, 2012

Andromeda Starburst Brightening up a giant galaxy September 12, 2012

The Sombrero II Two galaxies for the price of one July 2, 2012

The Sombrero Looking beneath the brim of a galaxy July 1, 2012

Galactic Streams Blending into the Milky Way March 21, 2012

Sagittarius Dwarf A galactic tug-of-war March 20, 2012

Satellite Galaxies Satellite galaxies for the Milky Way March 19, 2012

IC 342 A close but veiled cosmic pinwheel January 21, 2012

Featured Images

HST view of Messier 82

Busy Galaxy March 26, 2017

Galaxy map shows

Sailing Through the Galaxies February 13, 2017

sequence of images depicting the merger of M31 and Milky Way galaxies

Crash Course January 11, 2017

Hubble Space Telescope view of the galaxy NGC 1300

Star Bar December 18, 2016

Swirling Galaxy December 3, 2016

Hubble Space Telescope view of M63

Galactic Sunflower August 26, 2016

Elliptical galaxy NGC 1600

Biggest of the Big June 28, 2016

Galactic Baubles April 14, 2016

Ground-based view of Coma cluster of galaxies

Sparkling Galaxies March 29, 2016

Artist's concept of the galaxy WISE 2246

Evaporating Galaxy March 22, 2016

Hubble view of M51, the Whirlpool galaxy, and its companion galaxy

Whirling Along March 3, 2016

Strong winds blowing from a black hole in a distant spiral galaxy

Windy Black Hole January 15, 2016

The odd galaxy NGC 660

Busy Galaxy December 18, 2015

Hubble view of galaxy Markarian 231

Double Double November 22, 2015

Hubble Space Telescope image of spiral galaxy Messier 66

Evidence of an Encounter April 12, 2015

Hubble Space Telescope view of Abell 2744, a massive galaxy cluster

On the Frontier March 9, 2015

Hubble image of the aftermath of a galactic collisio

Beautiful Disruption January 30, 2015

Gemini Observatory image of VV 166 galaxy group

Galaxies Galore January 11, 2015

Hubble Space Telescope view of Tadpole Galaxy

Galactic Tadpole November 27, 2014

NGC 1398, a spiral galaxy in the constellation Fornax

Strangely Familiar August 23, 2014

Jetting Across the Universe August 12, 2014

A view of the busy Milky Way

Busy Galaxy July 24, 2014

Magellanic clouds above the ALMA radio telescope array

Cloudy Neighbors July 14, 2014

Combined visible, X-ray image of M51, the whirlpool galaxy

Colorful Whirlpool June 4, 2014

HST image of thousands of galaxies

Galaxies Galore April 17, 2014

The Condor galaxy

Night of the Condor March 15, 2014

Hubble Space Telescope view of M83 galaxy

Glowing Pinwheel January 10, 2014

Telescopic view of M33, the Triangulum Galaxy

Pirouetting Octopus November 10, 2013

Ultraviolet view of spiral galaxy NGC 6744 from the GALEX spacecraft

End of the Line June 29, 2013

Hubble Space Telescope image of M101

Stellar Pinwheel May 31, 2013

Hubble view of Coma Cluster of galaxies

Crowning Glory April 19, 2013

The Antennae galaxies

Getting Together April 16, 2013

Artist's concept of a distant quasar

Fiery Galaxy February 5, 2013

Hubble image of an edge-on galaxy, ESO 318-13

All that Glitters December 4, 2012

The nearby starburst galaxy IC 10

Active Neighbor October 8, 2012

Portion of Hubble Extreme Deep Field

Extreme Astronomy September 25, 2012

Andromeda and the Milky Way head for a galactic pile-up

Collision Course September 12, 2012

Hubble image of a pair of galaxies

Bright Companions September 7, 2012

Hubble Space Telescope view of M104, the Sombrero Galaxy

Galactic Hat Dance July 2, 2012

The remnants of two merged galaxies

Fast Exit June 18, 2012

Star Stream May 15, 2012

Combined X-ray, optical, and radio view of the galaxy Centaurus A

Busy Galaxy April 29, 2012

Space-based infrared view of the Large Magellanic Cloud

Busy Neighbor March 20, 2012

Optical and X-ray image of the galaxy cluster Abell 383

Brilliant Darkness March 16, 2012

New Heavyweight Champion February 6, 2012

Infrared view of the spiral galaxy IC 342

Tangled Galaxy January 22, 2012

Galactic Swirl December 14, 2011

NGC 4438 and NGC 4435, galaxies in Virgo

Beautiful Eyes August 25, 2011

NGC 3758, a system of two merging galaxies

Double Trouble June 11, 2011

X-ray and radio image of galaxy M87

Close to the Monster March 10, 2011

Irregular galaxy Henize 2-10, which appears to contain a supermassive black hole

Small But Powerful March 8, 2011

Spiral galaxy NGC 3621 in the constellation Hydra

Galactic Sparkler February 2, 2011

NGC 7252, aka the Atoms-for-Peace galaxies

Atomic Pile-up November 20, 2010

Six Spiral Galaxies from European Southern Observatory

Galaxies Galore October 29, 2010

Ground-based image of the galaxy cluster Abell 2151, in Hercules

Galaxies Galore October 1, 2010

NGC 4666, a starburst galaxy

Lively Galaxy September 3, 2010

M87 black hole

Busy Black Hole August 11, 2010

Galactic Beauty August 11, 2010

Cosmic Bullets July 20, 2010

An ultraviolet view of the spiral galaxy M81 shows young, hot stars in blue and

Grand Galaxy June 12, 2010

Beautiful Triplets March 8, 2010

Starry Neighbor February 26, 2010