Skip to main content
Galaxy Evolution

Celestial Tour: Galaxy Evolution

Within galaxies, most stars live out their lives--bursting to life, evolving over millions to billions of years, dying violently or slowly.

Galaxy Evolution
Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with NASA’s Universe of Learning partners: Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, NASA Jet Propulsion Laboratory, and Sonoma State University
All images, illustrations, and videos courtesy of NASA except:
  • Milky Way panorama courtesy of ESO/S. Brunier
  • Taurus constellation drawing from Firmamentum Sobiescianum sive Uranographia by Johannes Hevelius, courtesy of the United States Naval Observatory
  • Andromeda Galaxy image courtesy of Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF
  • Redshift animation courtesy of ESO
  • Centaurus A visible-light images courtesy of ESO
  • Written by Tracy Vogel
  • Designed by Marc Lussier
  • Music courtesy of Associated Production Music

An image of space filled with shining stars and spiral-shaped clouds of galaxies. Text, Galaxies are where the action happens in our universe, islands of motion and change in the vastness of space.
Within galaxies, most stars live out their lives -- bursting to life, evolving over millions to billions of years, dying violently or slowly. An image of a nebula formed of reddish clouds surrounding a cluster of bright blue white stars.
Text, To understand the universe we must understand galaxies. Variously shaped galaxies appear and fade into the background.
Other galaxies are too far away for us to reach.
Even if we could travel at the speed of light it would still take us 2.5 million years to reach the closest large galaxy, Andromeda. An image of a disk-shaped galaxy with cloudy arms spiralling out from a bright glowing white center.
Text, so we must study galaxies from afar.
A computer simulation of glowing objects spinning and colliding in darkness. Text, Our understanding is also complicated by time. Galaxies grow and evolve over billions of years -- too slowly for us to observe the changes happening in real time.
Fortunately, we can see galaxies as they were at different times in the past.
An illustration of many galaxies arranged in transparent layers. The closest layer is labeled light from nearby galaxies. The most distant layer is labeled light from distant galaxies. Text, Light moves quickly but it still takes time to travel through space. Arrows move from the distant to the nearby galaxies.
Text, Light from more distant galaxies takes longer to reach us. The arrow from the most distant galaxies continues to move while the closer arrow has stopped.
Text, When we capture this light we see galaxies as they appeared with that light started traveling. For distant galaxies, we see them as they were billions of years ago. Images of small galaxies in spiral, disk, or dot shapes and blue, red, and yellow colors.
Distant developing galaxies appear as tiny dots. Nearby developed galaxy appears as a large spiral. Text, by looking at different distances, we can observe galaxies at different ages and stages of development.
An animation of waves of light moving from a galaxy to earth. Text, But as light travels through the expanding universe, it become stretched by the expansion of space.
Visible light changes to infrared light. The light wave turns red as it approaches earth.
Text, to see distant early galaxies we must look for this infrared light. A nebula spins in the background.
Infrared light is invisible to our eyes but not to NASA's James Webb Space Telescope.
An animation of the telescope unfolding itself in space, expanding two long arms in the front and back and stretching two panels open to the sides, forming a reflective silver diamond shaped surface under a panel of golden hexagonal plates that unfold to form a disc framed by long rods that connect at a point. Text, Webb is the largest and most sensitive infrared space telescope ever built. With its position far from Earth and its giant mirror, Webb will capture infrared light never seen before.
The telescope near a red galaxy. Text, its powerful infrared vision opens up previously undiscovered realms of the universe.
A point flashes bright purple and white on a black background. Text, Webb can observe the first galaxies flickering to life after the big bang.
An image of space filled with galaxies. Text, Webb now turns its gaze on the universe's most distant galaxies, the tiny galaxy building blocks that became the graceful spirals and glowing ellipticals we know today.