System Archive

Irregular galaxies do not fit neatly into spiral or elliptical categories. Their shapes are often distorted by gravitational interactions or past collisions.

Despite their disorder, many irregular galaxies are rich in gas and actively forming stars. They can be surprisingly bright and energetic.

Studying irregular galaxies helps astronomers understand how interactions reshape galaxies over time.

When galaxies collide, they pass through each other over hundreds of millions of years. Individual stars almost never collide due to vast distances, but gravity distorts entire systems.

Gas clouds compress, triggering massive star formation. Spiral arms stretch, warp, or vanish entirely. Over time, two galaxies can merge into a single, larger one.

Our Milky Way is on course to merge with the Andromeda Galaxy in several billion years.

Galaxies rotate too fast to be held together by visible matter alone. The solution to this mystery is dark matter — an invisible form of matter that interacts through gravity.

Dark matter forms massive halos around galaxies, providing the gravitational glue that keeps them intact. Without it, galaxies would tear themselves apart.

Although we cannot directly observe dark matter, its influence is undeniable at galactic scales.

Galaxy clusters are the largest gravitationally bound structures in the universe. They contain hundreds or thousands of galaxies, along with vast amounts of hot gas and dark matter.

The space between galaxies in a cluster is not empty. It is filled with superheated plasma that emits X-rays, revealing the cluster’s true mass.

Clusters trace the large-scale structure of the universe and help astronomers study dark matter and cosmic evolution.

On the largest observable scales, galaxies are not evenly spread. They form a cosmic web of filaments, clusters, and vast empty voids.

Dark matter shapes this structure, guiding where normal matter collects and galaxies form. The result looks like a three-dimensional spiderweb spanning the universe.

This structure shows that gravity has shaped the universe from its earliest moments to the present day.

A galaxy is a vast, self-contained system of stars, gas, dust, and dark matter bound together by gravity. For much of history, galaxies were called “island universes” because they are separated by enormous distances of empty space.

Galaxies are not static. Stars orbit the galactic center, gas clouds collapse to form new stars, and older stars drift through long, stable paths. On the largest scales we can observe, galaxies are the basic building blocks of the visible universe.

Understanding galaxies is a major step up in scale. You are no longer studying individual objects, but entire systems containing billions of stellar lives happening at once.

The Milky Way is the galaxy we live in. From Earth, we see it as a faint band of light stretching across the sky — this is our edge-on view of its disk.

The galaxy has a central bulge, spiral arms, and a bar-like structure through its core. At the very center lies a supermassive black hole, around which everything else orbits.

Our Sun is located in a quiet region of one spiral arm, far from the crowded and energetic galactic center. One full orbit around the Milky Way takes the Sun about 230 million years.

Spiral galaxies are among the most visually striking objects in astronomy. They feature graceful arms winding outward from a central bulge, embedded in a rotating disk.

These arms are regions where gas is compressed, triggering new star formation. Young, hot stars light up the arms, while older stars populate the disk and bulge.

Spiral galaxies are dynamic systems, balancing rotation, gravity, and ongoing stellar birth.

Elliptical galaxies range from small, faint systems to enormous giants containing trillions of stars. They have little gas and dust, which means new star formation is rare.

Most stars in ellipticals are old and red, indicating that these galaxies formed their stars early and then settled into quiet evolution.

Elliptical galaxies are common in dense environments like galaxy clusters, where interactions strip gas and disrupt spiral structures.