Tracing the Growth of Galaxies

Hubble is instrumental in uncovering the various stages of galactic evolution.

Hubble Ultra Deep Field (2014)

Like documenting a child’s development in a scrapbook, astronomers use Hubble to capture the appearance of many developing galaxies throughout cosmic time. This is possible because of the mathematical relationship between cosmic distance and time: the deeper Hubble peers into space, the farther back it looks in time. This occurs because light travels at a fast, but finite speed, and it takes time to travel the incredible distance from galaxies far, far away. When this light finally reaches Earth, it shows us the object as it appeared at the time its light was emitted. As it happens, the most distant and earliest galaxies spied by Hubble are smaller and more irregularly shaped than today's grand spiral and elliptical galaxies. This is evidence that galaxies grew over time through mergers with other galaxies to become the giant systems we see today.

The field of view is filled with galaxies in all shapes, sizes, colors, and galaxy types.  All against a black backdrop.
Hubble’s Ultra Deep Field is one of the most distant looks into space ever. The cumulative exposure time needed to capture the image was about a million seconds (11 days).
NASA, ESA, S. Beckwith (STScI) and the HUDF Team

Because the universe was smaller in the past, galaxies were more likely to interact with one another gravitationally. Some of Hubble’s cosmic “snapshots” show fantastic stellar streamers pulled out and flung across space by colliding galaxies. They apparently settled over time into the more familiarly shaped galaxies seen closer to Earth and hence nearer to the present time. By carefully studying galaxies at different epochs, astronomers can see how galaxies changed and evolved over time. Among the things they investigate are the relative amounts of stars and gas in galaxies, the types and amounts of identifiable chemical elements they hold, and star-formation rates.

This scientific visualization flies through a 3D model of the HUDF galaxies. Each of the more than 5,000 galaxies in the model was cut out of the HUDF image and placed at its appropriate distance (as calculated from redshift measurements). The virtual camera flies through this long, thin galaxy dataset, showing how galaxy sizes, shapes, and colors change as one looks both out in space and back in time. Note that, in order to traverse the cosmos in a reasonable amount of time, the distance scale in the model was compressed by a factor of a few hundred. Credit: NASA, ESA, and G. Bacon, T. Borders, L. Frattare, Z. Levay and F. Summers (STScI)
Faint, distant galaxies, observed by Hubble. They are arranged on four columns and seven rows. Most appear as red splotches. A few of the images also hold regions of yellow, blue, and or green pixels.
A sample of the faintest and farthest galaxies in the Hubble Ultra Deep Field shows that they were irregularly shaped and frequently interacting in the distant past.
NASA, ESA, R. Bouwens and G. Illingworth (University of California, Santa Cruz)

Hubble observations of our neighboring galaxy, the Andromeda galaxy (M31), show that the galaxy is moving ever closer to an inevitable collision with our own Milky Way galaxy.

Andromeda is currently 2.5 million light-years away, but it and the Milky Way are moving toward each other under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both. The merger will begin about four billion years from now and will likely result in the creation of a giant elliptical galaxy.

This simulation shows the view of the night sky throughout the merger of our Milky Way galaxy and the neighboring Andromeda galaxy.
NASA, ESA, Z. Levay, R. van der Marel and G. Bacon (STScI), T. Hallas and A. Mellinger

Explore Other Hubble Science Highlights

Learn about some of Hubble's most exciting scientific discoveries.

Cepheid star in Andromeda galaxy (Hubble observations)

Discovering the Runaway Universe

Our cosmos is growing, and that expansion rate is accelerating.

Hubble image left to right: Jupiter, Uranus, Saturn, Neptune

Studying the Outer Planets and Moons

Hubble’s systematic observations chart the ever-changing environments of our solar system's giant planets and their moons. 

Hubble view of an expanding halo of light around star v838 monocerotis

Seeing Light Echoes

Like ripples on a pond, pulses of light reverberate through cosmic clouds forming echoes of light.

Hubble observations of galaxies' centers

Monster Black Holes are Everywhere

Supermassive black holes lie at the heart of nearly every galaxy.

Hubble observations of Carina Nebula section

Exploring the Birth of Stars

Hubble’s near-infrared instruments see through the gas and dust clouds surrounding newborn stars.

An oval of colorful tendrils of gas and dust stretching from lower-left to upper right. Ova's outer ring is rusty-red tendrils, followed by a yellow/lime-green ring of tendrils. Oval's center is bright turquoise with white tendrils bisecting it. All set on a black background.

The Death Throws of Stars

From colliding neutron stars to exploding supernovae, Hubble reveals details of some of the mysteries surrounding the deaths of stars. 

depiction of gravitational lensing

Shining a Light on Dark Matter

Hubble’s observations help astronomers uncover the underlying structure of the universe.

Thirty proplyds in a 6 by 5 grid. Each one is unique. Some look like tadpoles, others like bright points in a cloudy disk.

Finding Planetary Construction Zones

Hubble’s sensitivity can reveal great disks of gas and dust around stars.

Three views of Pluto. Three mottled circles in colors of yellow, grey, rusty-orange, and black.

Uncovering Icy Objects in the Kuiper Belt

Hubble’s discoveries helped NASA plan the New Horizon spacecraft’s flyby of Pluto and beyond.

Comma shaped curved cloud of gases in bright white edged with bright-pink star forming regions, and threaded with rusty-brown tendrils of dust at center and throughout the comma shaped merger. All set against the black of deep space.

Galaxy Details and Mergers

Hubble’s observations reveal a menagerie of galaxies.

Blue background. Center of image is a disk blocking the light of a star. Below and just to the left of the disk, at about seven o'clock, is a bright white point. This is PDS 70b.

Recognizing Worlds Beyond Our Sun

Hubble’s unique capabilities allow it to explore planetary systems around other stars. 

animation of a binary asteroid with a shifting tail

Tracking Evolution in the Asteroid Belt

These conglomerates of rock and ice may hold clues to the early solar system.