Galaxies

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

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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

Date Discovery
June 29, 2020 Birds of a Feather (NGC 2275)
June 15, 2020 A Bright Find (PLCK G045.1+61.1)
June 1, 2020 Stellar Snowflakes (NGC 6441)
May 18, 2020 Stellar Glitter in a Field of Black (ESO 461-036)
May 11, 2020 Bending the Bridge Between Two Galaxy Clusters (Abell 2384)
April 6, 2020 Rings Upon Rings (NGC 2273)
February 20, 2020 Beyond the Brim, Sombrero Galaxy's Halo Suggests a Turbulent Past
February 3, 2020 Nature's Grand Design (NGC 5364)
January 28, 2020 Chandra Spots a Mega-Cluster of Galaxies in the Making
January 27, 2020 Bars and Baby Stars (NGC 7541)
January 16, 2020 XMM-Newton Discovers Scorching Gas in Milky Way's Halo
January 6, 2020 Hubble Surveys Gigantic Galaxy (UGC 2885)
January 5, 2020 New View of Milky Way’s Center
January 5, 2020 Distant Galaxy Group Driving Ancient Cosmic Makeover
December 31, 2019 Galactic Pyrotechnics From 23 Million Light Years Away (NGC 4258)
December 18, 2019 GISMO Instrument Maps Inner Milky Way, Sees Cosmic ‘Candy Cane’
December 17, 2019 Galaxy Gathering Brings Warmth (NGC 6338)
December 16, 2019 Discs and Bulges (IC 2051)
December 10, 2019 How to Shape a Spiral Galaxy (NGC 1068)
December 9, 2019 Galactic Diversity (NGC 3175)
November 20, 2019 Hubble Studies Gamma-Ray Burst with the Highest Energy Ever Seen (GRB 190114C)
November 18, 2019 Emission Versus Absorption (NGC 3749)
November 18, 2019 A Weakened Black Hole Allows its Galaxy to Awaken
November 11, 2019 A Rival to the Milky Way (NGC 772)
November 7, 2019 The Sunburst Arc (PSZ1 G311.65-18.48)
October 24, 2019 Mega-Cluster of Galaxies in the Making
October 21, 2019 A Familiar Sight (IC 4653)
October 17, 2019 Super Spirals Spins Super Fast
October 10, 2019 Audit of the Milky Way’s Gas Flow Rates Reveals a Mysterious Surplus of Inflowing Gas
September 16, 2019 Not So Dead After All (Messier 110)
July 29, 2019 Feeling Edgy (NGC 3432)
July 15, 2019 A Beautiful Whorl (NGC 2985)
July 8, 2019 Galactic Cherry Blossom (NGC 1156)
May 20, 2019 Come a Little Closer (Messier 90)
May 16, 2019 Creative Destruction as Galaxies Collide (NGC 4485)
May 8, 2019 New Clues About How Ancient Galaxies Lit up the Universe
May 6, 2019 Distant and Ancient (SPT-CL J0615-5746)