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 to 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.

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



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?


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

Date Discovery
July 11, 2016 'Frankenstein' Galaxy Surprises Astronomers (UGC 1382)
July 11, 2016 A Lonely Birthplace  (MCG+07-33-027)
July 4, 2016 A Stubborn Dwarf Galaxy (LEDA 677373)
June 27, 2016   Bursting at the Seams (NGC 1569)
May 9, 2016 A Spiral Snowflake  (NGC 6814)
April 18, 2016 Elegance Conceals an Eventful Past (NGC 4111)
March 31, 2016 Journey to the Center of Our Galaxy
March 28, 2016 A Distinctly Disorganized Dwarf (UGC 4459)
March 10, 2016 Telescopes Combine to Push Frontier on Galaxy Clusters
March 3, 2016 New Cosmic Distance Record (GN-z11)
January 28, 2016 Monstrous Cloud Boomerangs Back to Our Galaxy
January 25, 2016 A Misbehaving Spiral (LO95 0313-192)
January 15, 2016 Most Luminous Galaxy is Ripping Itself Apart (W2246-0526)
January 7, 2016 NASA's Great Observatories Weigh Massive Young Galaxy Cluster
January 6, 2016 Spitzer, Hubble Find 'Twins' of Superstar Eta Carinae in Other Galaxies
January 5, 2016 Andromeda Galaxy Scanned with High-Energy X-ray Vision
January 4, 2016 Supermassive and Super-hungry (NGC 4845)
December 21, 2015 Chandra Finds Remarkable Galactic Ribbon Unfurled (Zwicky 8338)
December 14, 2015 A Home for Old Stars (Terzan 1)
December 3, 2015 NASA Telescopes See Magnified Image of the Faintest Galaxy from the Early Universe
December 2, 2015 Cosmic Filaments Exposed Near Huge Cluster
November 23, 2015 The Last Waltz (2MASX J16270254+4328340)
November 23, 2015 Where Alice in Wonderland Meets Albert Einstein (SDSS J103842.59+484917.7)
November 13, 2015 Fermi Finds Hints of Gamma-ray Cycle in an Active Galaxy
November 3, 2015 A Giant Gathering of Galaxies (MOO) J1142+1527)
November 2, 2015 At the Center of the Tuning Fork
October 26, 2015 Suzaku Finds Common Chemical Makeup at Largest Cosmic Scales
October 22, 2015 Frontier Fields View of MACSJ0416.1-2403
September 30, 2015 A Fresh Perspective on an Extraordinary Cluster of Galaxies (Phoenix Cluster)
September 10, 2015 NASA Telescopes Find Galaxy Cluster with Vibrant Heart
September 9, 2015 Hubble Uncovers Clues of Earliest Galaxies
August 26, 2015 Chandra Data Suggest Giant Collision Triggered "Radio Phoenix" (Abell 1033)
August 6, 2015  Hubble Finds Evidence of Galaxy Star Birth Regulated by Black-Hole Fountain