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

 

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
February 22, 2021 Eye in the Sky (NGC4826)
January 18, 2021 Colors of the Lost Galaxy (NGC 4535)
January 14, 2021 Magnetic Chaos Hidden Within the Whirlpool Galaxy
January 12, 2021 NASA Missions Help Investigate an ‘Old Faithful’ Active Galaxy
 January 7, 2021 Hubble Showcases 6 Galaxy Mergers
December 21, 2020 Faint Remnant Threads (NGC 1947)
December 7, 2020 The Stellar Forge (NGC 1792)
November 18, 2020 16-Year-Old Cosmic Mystery Solved, Revealing Stellar Missing Link
November 9, 2020 Contorting Giants (LRG-3-817)
October 26, 2020 Beauty From Chaos (NGC 34)
September 22, 2020 Data Sonification: Sounds from Around the Milky Way
August 27, 2020 Hubble Maps a Giant Halo Around the Andromeda Galaxy
August 25, 2020 NASA Missions Explore a ‘TIE Fighter’ Active Galaxy
August 10, 2020 Ring of Stellar Wildfire (NGC 1614)
July 13, 2020 A frEGGs-cellent Discovery  (J025027.7+600849)
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)