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Milky Way Galaxy

Our home galaxy. The Milky Way is a spiral galaxy with four major arms containing young bright stars, gas, and dust. The mass of the Milky Way is estimated to be between 400 billion and one trillion times the mass of the Sun. The Milky Way’s diameter is about 100,000 light-years, with the Sun orbiting about 27,000 light-years from the galactic center. However, most of the galaxy’s mass consists of “dark matter” which encircles the Milky Way’s disk in a vast halo. Dark matter may account for 90 percent of the Milky Way’s mass.

Resources

Facts and Figures June 10, 2010
The Sun and our solar system lie in the "thin disk" of our galaxy.

The Milky Way May 21, 2010

Radio Programs

Shredded Cluster Shredding an ancient star cluster August 17, 2016

Dark Downtown? The glow of the galaxy’s busy downtown August 16, 2016

Smith’s Cloud A big cloud falls toward the Milky Way August 14, 2016

Milky Way Hiding behind a cosmic haze July 29, 2016

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

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

Winter Milky Way Adding to the winter Milky Way January 27, 2016

Sculptor Looking into a galactic well December 10, 2015

Faintest Cluster A faint cluster that’s doomed October 3, 2015

Far, Far Away Mapping the distance to the galactic center August 13, 2015

Galactic Hub Visiting downtown Milky Way August 12, 2015

Sagittarius Steaming up the center of the galaxy August 11, 2015

Fermi Bubbles Blowing bubbles in the Milky Way July 19, 2015

Stellar Metals A difference between young and old stars July 14, 2015

Omega Centauri Alien visitors from other galaxies May 25, 2015

M92 An ancient family of stars May 12, 2015

North Poles Looking north from the Milky Way May 8, 2015

Orion Arm A short “arm” of the Milky Way February 17, 2015

Winter Milky Way Looking toward the galaxy’s outskirts February 16, 2015

Survivor The heart of the galaxy stays quiet January 11, 2015

Distant Neighbors The Milky Way’s lonely outskirts December 16, 2014

Distant Hub Looking into the past of our home galaxy September 29, 2014

WIMP-y Glow Bright evidence of dark matter July 29, 2014

Dark Center Darkness in the heart of the galaxy July 28, 2014

The Brick Building a future stellar nursery July 27, 2014

Galactic Track A roller-coaster ride around the galaxy July 26, 2014

Sagittarius A steaming teapot in the southern sky July 23, 2014

Magellanic Collision New stars from a galactic collision July 14, 2014

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

North Galactic Pole Gazing away from the Milky Way April 11, 2014

Runaway Stars Stars that are leaving home in a hurry April 10, 2014

Moon in the Middle Bright stars packed around the Moon April 4, 2014

Spring Milky Way The Milky Way brackets the night sky March 27, 2014

Galactic Archaeology Digging into the history of the galaxy March 23, 2014

Gaia II Mapping a billion stars October 3, 2013

Local Arm Wrapping our arms around our home galaxy September 3, 2013

Counting Stars Counting the stars in the Milky Way July 25, 2013

Black Hole Beacon A black hole announces its presence July 24, 2013

Galactic Bubbles Keeping food from a black hole July 23, 2013

Good Neighborhood A good neighborhood for young stars? July 22, 2013

Sagittarius A teapot in the southern sky July 21, 2013

The Antennae Seeing the future of the Milky Way April 15, 2013

Groombridge 1830 An interloper from a distant realm March 30, 2013

Milky Way Matters The Milky Way bulks up February 8, 2013

M2 A distant home for old stars January 5, 2013

Star Populations Segregating the stars of the Milky Way December 2, 2012

Collision Course Taking aim at another galaxy September 11, 2012

Andromeda Galaxy A galactic twin in the evening sky September 10, 2012

Arcturus Tracing a star’s origins August 27, 2012

Pipe Nebula Lighting up a dark nebula June 16, 2012

Future Neighbor A future close neighbor to the Sun June 13, 2012

‘Milky’ Way The “milky” band of the Milky Way June 9, 2012

Hercules Cloud Piling up stars in the outer galaxy May 23, 2012

Cosmic Clocks The ticking of cosmic clocks April 11, 2012

Snack Time Snack time for a giant black hole March 28, 2012

Alien Clusters Alien visitors from other galaxies March 22, 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

Winter Milky Way III Getting armed for a trip through the galaxy February 16, 2012

Winter Milky Way II Enlivening the galactic suburbs February 15, 2012

Winter Milky Way Following a galactic pathway February 14, 2012

Alpha Persei Cluster Tracing a galactic cataclysm October 8, 2011

Robert Trumpler Filling the space between the stars October 1, 2011

Milky Way’s Heart V Youngsters at the heart of the Milky Way September 29, 2011

Milky Way’s Heart IV The flashy heart of the Milky Way September 28, 2011

Milky Way’s Heart III Confirming the dark heart of the Milky Way September 27, 2011

Milky Way’s Heart II A sky-spanning marquee of stars September 26, 2011

Milky Way’s Heart Taking a peek at a busy downtown September 25, 2011

Thomas Wright Giving birth to a galaxy September 20, 2011

M2 An ancient family of stars September 16, 2011

Future Skies The universe in the year one trillion August 29, 2011

Speedy Star Measuring the Milky Way with a single star February 17, 2011

Winter Milky Way The bright and dark Milky Way January 29, 2011

Featured Images

Map of the Milky Way's spiral arms

Starry Arms July 25, 2016
Multi-wavelength view of the center of the Milky Way galaxy

Galactic Hub August 13, 2015
Artist's concept of Fermi bubbles

Blowing Bubbles July 20, 2015
Hubble Space Telescope view of the core of M13, a globular cluster in Hercules

Old Sparklers May 12, 2015
G2 survives its swing around the black hole at the center of the Milky Way

Narrow Escape March 27, 2015
The Milky Way galaxy's spiral arms

Arming the Milky Way February 18, 2015
Artist's concept of hot gas funneling toward black hole at center of Milky Way

Dark Center July 29, 2014
A view of the busy Milky Way

Busy Galaxy July 24, 2014
The Milky Way glows above the Nevada desert

Dig Site March 24, 2014
Artist's concept of the Milky Way galaxy and its dark matter halo

Illuminating the Darkness February 9, 2013
Multispectral view of giant star-forming regions at the center of the Milky Way

Molecule Factory November 13, 2012
Andromeda and the Milky Way head for a galactic pile-up

Collision Course September 12, 2012
Artist's concept of stars and a gas cloud near the Milky Way's central black hol

Snack Time March 29, 2012
Two globular clusters; a previously known one at right, and a new one in circle

Star City October 19, 2011
Stars and gas swirl around the black hole at the center of the Milky Way

Swirling Center September 27, 2011
Artist's concept of a free-floating planet in the Milky Way galaxy

Free Agent May 19, 2011

Cold Fingers March 19, 2010