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
March 14, 2022 Eye of the Galaxy (NGC 1097)
March 9, 2022  Tilted Galaxy Turns Studies Topsy-Turvy
February 22, 2022 Hubble Looks at a ‘Space Triangle’ Spawned by a Galaxy Collision
February 7, 2022 A Cosmic Draw (Arp 282)
January 24, 2022 Strike! (NGC 7764A)
January 12, 2022 1,000-Light-Year-Wide Bubble Surrounding Earth Is Source of All Nearby, Young Stars
December 16, 2021 Our Milky Way May Be More Fluffy, Less Wiry
October 11, 2021 Invisible Galactic Gale (NGC 4666)
October 7, 2021 'Double' Galaxy Mystifies Hubble Astronomers
August 23, 2021 Cluster in the Cloud (NGC 2164)
July 15, 2021 Chandra Catches Slingshot During Collision (Abell 1775)
July 2, 2021 Galaxy Cluster Travels Down an Intergalactic Highway (Northern Clump)
July 1, 2021 Chandra Turns Up the Heat in the Milky Way Center
May 27, 2021 Magnetized Threads Weave Spectacular Galactic Tapestry (Galactic Center)
April 21, 2021 Astronomers Release New All-Sky Map of Milky Way’s Outer Reaches
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