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Galaxies

Universe Galaxies-1 Milky Way

Artist's Conception - The Milky Way
Where are we?
We live in a somewhat remote arm of the Milky Way. This video shows you the way from our home to a vantage point outside the Local Group.
Animation (Quicktime, 3MB)

Universe Galaxies-3 Deep Field
Hubble Ultra Deep Field galaxies:
Credit: NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Our galaxy, the Milky Way, is typical: it has hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together. And it’s all held together by gravity.

Like more than two-thirds of the known galaxies, the Milky Way has a spiral shape. At the center of the spiral, a lot of energy and, occasionally, vivid flares. are being generated. Based on the immense gravity that would be required explain the movement of stars and the energy expelled, the astronomers conclude that the center of the Milky Way is a supermassive black hole.

Other galaxies have elliptical shapes, and a few have unusual shapes like toothpicks or rings. The Hubble Ultra Deep Field (HUDF) shows this diversity. Hubble observed a tiny patch of sky (one-tenth the diameter of the moon) for one million seconds (11.6 days) and found approximately 10,000 galaxies, of all sizes, shapes, and colors. From the ground, we see very little in this spot, which is in the constellation Fornax.

Formation

After the Big Bang, the Universe was composed of radiation and subatomic particles. What happened next is up for debate - did small particles slowly team up and gradually form stars, star clusters, and eventually galaxies? Or did the Universe first organize as immense clumps of matter that later subdivided into galaxies?

Collisions

The shapes of galaxies are influenced by their neighbors, and, often, galaxies collide. The Milky Way is itself on a collision course with our nearest neighbor, the Andromeda galaxy. Even though it is the same age as the Milky Way, Hubble observations reveal that the stars in Andromeda's halo are much younger than those in the Milky Way. From this and other evidence, astronomers infer that Andromeda has already smashed into at least one and maybe several other galaxies.

Recent Discoveries

April 30, 2013 Colossal Hot Cloud Envelopes Colliding Galaxies (NGC 6240)
May 6, 2013 A Tale of Galactic Collision (2MASX J05210136-2521450)
May 13, 2013 A Spacetime Magnifying Glass (Abell S1077)
May 16, 2013 Galactic Wheels within Wheels (Messier 94)
May 22, 2013 Herschel Finds Galaxy Mega Merger
May 27, 2013 The Messy Results of a Galactic Collision (ESO 576-69)
June 3, 2013 Best Ultraviolet Maps of the Nearest Galaxies (LMC and SMC)
June 11, 2013 Mapping Invisible Pools of Gas in our Galaxy
June 20, 2013 Colliding Galaxy Pair Takes Flight (NGC 2936 and NGC 2937)
June 24, 2013 Inseparable Galactic Twins (PGC 9074 and PGC 9071)
July 15, 2013 A Stranger in the Crowd (NGC 4866)
August 1, 2013 Monster in the MIddle: Brightest Cluster Galaxy
August 8, 2013 Hubble Finds Source of Magellanic Stream
August 14, 2013 Dwarf Galaxy Caught Ramming into a Large Spiral (NGC 1232)
August 15, 2013 True Shapes of Galaxies 11 Billion Years Back in Time
August 22, 2013 Barred Sculptor Galaxy
September 19, 2013 Clues to the Growth of the Colossus (in Coma Cluster)
April 23, 2013 Galaxy Goes Green in Burning Stellar Fuel
April 4, 2013 Taken Under the "Wing" of the Small Magellanic Cloud
April 1, 2013 Light and Dust in a Nearby Starburst Galaxy
February 21, 2013 Stellar Motions in Outer Halo (Milky Way)
January 28, 2013 The Moment the Lights Went Out
January 10, 2013 Largest-Known Spiral Galaxy (NGC 6872)
December 17, 2012 The Needle Galaxy (IC 2233)