40 Of The Most Mesmerizing Galaxies Captured On Telescope

Most galaxies are between 10 billion and 13.6 billion years old and some are almost as old as the universe itself, which formed around 13.8 billion years ago. Some of the oldest galaxies observed formed when the universe was only about a billion years old. The scientists think those galaxies started to grow around pockets of space that were slightly denser than their surroundings, an effect created by cosmic inflation when the universe began.

Galaxies consist of stars, planets, and vast clouds of gas and dust, all held together by gravity. The largest one contain trillions of stars and could be more than a million light-years across. The smallest may contain a few thousand stars and span just a few hundred light-years. Most large galaxies have supermassive black holes at their centers, some with billions of times the Sun’s mass.

Before the 20th century, people didn't know other galaxies than the Milky Way; earlier astronomers had classified them as as “nebulae,” since they looked like fuzzy clouds.

It all changed in the 1920s when the astronomer Edwin Hubble showed that the Andromeda “nebula” was a galaxy in its own right. Despite the immense distance, Andromeda is the closest large galaxy to our Milky Way, and it's bright enough in the night sky that it's visible to the naked eye in the Northern Hemisphere.

In 1936, because of Hubble, galaxies were grouped into four main types: spiral galaxies, lenticular galaxies, elliptical galaxies and irregular galaxies.

Interestingly enough, more than two-thirds of all observed galaxies are spiral galaxies that have a flat, spinning disk with a central bulge surrounded by spiral arms.

Elliptical galaxies contain many older stars, but little dust and other interstellar matter. Their stars orbit the galactic center but they do so in more random directions. The universe's largest known one may contain up to a trillion stars and span two million light-years across.

Lenticular galaxies, such as the funny Sombrero Galaxy, are between elliptical and spiral galaxies. They have a thin, rotating disk of stars and a central bulge, but they don't have spiral arms. Like elliptical galaxies, they have little dust and interstellar matter, and they seem to form more often in densely populated regions of space.

The rest of the galaxies are called Irregular - such as the Large and Small Magellanic Clouds. They appear misshapen and lack a distinct form, very often because they are within the gravitational influence of other galaxies close by. They are full of gas and dust, which makes them great nurseries for forming new stars.

Some galaxies are quite often parts of larger associations known as groups, clusters, and superclusters. For example, the Milky Way is in the Local Group, a galaxy group about 10 million light-years across that also includes the Andromeda galaxy and its satellites.

Sometimes, galaxies collide. Astronomers think the Milky Way and its galactic neighbor Andromeda are set to collide in another 4.5 billion years.

If colliding galaxies don’t have enough momentum to move past each other, they can merge to form a single larger galaxy. Then it can look very different from the two that created it. For example, if a spiral and elliptical merge, the result could be an irregular galaxy.

Some larger galaxies can also eat up the smaller ones through proximity and gravitational interactions, pulling material away to fuel their own growth.

In 2004, NASA released the Hubble Ultra Deep Field: a tiny part of the constellation Fornax contained around 10,000 galaxies, some of which existed 13 billion years ago, less than 800 million years after the big bang. These types of snapshots are very important for scientists to be able to study galaxies at different evolutionary stages.

Nearly 10,000 galaxies that were captured in the Hubble Ultra Deep Field may look like they’re randomly scattered across the sky yet they are often part of larger structures and superstructures in space. 

Galaxies, galaxy groups and clusters, superclusters, and galactic walls are arranged in twisting, threadlike structures called the cosmic web. The web forms as the gravitational attraction of the universe’s matter draws larger and larger objects together leading to concentrations of galaxies with voids of space in between, as if the galaxies were resting on empty bubbles. In the places where those concentrations intersect, they form larger structures like clusters and walls. The cosmic web forms a sort of scaffolding that cradles everything that exists within the universe.