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
December 17, 2018 Abell 2744
November 15, 2018 To Boldly Go into Colliding Galaxy Clusters (Abell 1033)
November 5, 2018 Feeling Blue (ESO 338-4)
October 22, 2018 A Galaxy with a Bright Heart (NGC 5033)
October 8, 2018 Rings Upon Rings (NGC 3351)
September 27, 2018 Making Head or Tail of a Galactic Landscape (Abell 2142)
June 4, 2018 Threads of Blue (IC 4870)
May 31, 2018 Peculiar Galaxy (NGC 3256)
May 21, 2018 Between Local and Laniakea (SDSS J0333+0651)
May 17, 2018 Astronomers Release Most Complete Ultraviolet-Light Survey of Nearby Galaxies
April 30, 2018 A Spiral Disguised (NGC 1032)
April 30, 2018 Monster in the Deep (SDSSJ0150+2725)
April 23, 2018 Stuck in the Middle (Lenticular galaxy NGC 2655)
April 3, 2018 Scientists Surprised by Relentless Cosmic Cold Front - Perseus Cluster
March 19, 2018 A Red, Metal-rich Relic - NGC 1277
March 12, 2018 Arrested Development: Hubble Finds Relic Galaxy Close to Home (NGC 1277)
February 26, 2018 A Frenzy of Stars - IC 4710
February 12, 2018 Improved Hubble Yardstick Gives Fresh Evidence for New Physics in the Universe
February 6, 2018 The Loneliest Firework Display - NGC 1559
January 29, 2018 Twins with Difference (NGC 7331)
January 11, 2018 NASA’s Great Observatories Team Up to Find Magnified and Stretched Out Image of Distant Galaxy
January 11, 2018 Hubble Probes the Archeology of Our Milky Way's Ancient Hub
January 8, 2018 A Gargantuan Collision (ACT-CLJ0102-4915)