A Look Back in Time to Understand Galaxy Formation

The study of galaxy formation is largely concerned with how the evolution of a predominantly homogenous galaxy from a predominantly heterogeneous pool of stars, how galaxies vary over time, and how the various processes which produced the diversity of modern-day galaxies are linked.

Using computer simulations to understand the process.

By using computer simulations, astronomers can study galaxy formation and evolution much more precisely than is possible by simply studying the history of individual stars within a galaxy. Simulations are also able to be used to study a wide variety of different physical processes. These include quasars, which are extremely active; supernovae, which are explosions of black-hole energy; and pulsars, which emit signals that are picked up by orbiting telescopes. All these processes have effects on the formation and growth of stars within a galaxy.

Galaxy formation occurs when clouds of dust are lofted into space by winds. 

Many of these clouds are made of neutral gas such as protons and deuterium. Over time, these clouds become dense and move into a region where they are surrounded by cold gas (neutron vapor). This cold gas makes the wind flow much slower than it was before. Eventually, this causes clouds to grow large enough that their gravitational pull pulls the gas together, resulting in clouds of gas and dust that make up a developing galaxy.

Where can a galaxy formation be found?

While a galaxy formation is most often found along very close to its parent universe, it can also be found much farther out. In fact, astronomers frequently find galaxies outside of our own local group. A recent study showed that nearly half of all galaxies lie well outside of our halo of about 12 solar cells in distance. If this is true, it shows that almost all of our Milky Way’s mass is composed of a filament of dark matter that originated far out in the universe. While this filament is very distant, it is remarkably close to our own galaxy, which means that it could be quite young.

The filament would have to be very old if it is cooling off quickly enough to allow stars to form, because clouds with very low temperatures do not contain any dark matter at all. In order for clouds to form, however, stars need to have a temperature of at least about 1000 degrees Celsius. If this temperature is not present, the stars cannot form. This is what is known as the ‘cosmos’ in modern cosmology. In short, it is believed that our galaxy formed in a separate universe, one that is substantially cooler and contains no dark matter at all.

Another alternative to the galaxy formation theory.

This is the theory that the universe was not created equally. Particles within the halo, some of which are made of neutral gas, may have been left behind by collisions within other parts of the universe. After the big bang, smaller less heavy collisions could have contributed to the creation of very heavy elements such as iron, nickel, or aluminum. Many of these elements are known to be very common within the earth’s crust.

When the universe began to fill with stars, it formed dense clouds of gas. 

These clouds would have been extremely hot, with nearly all of them containing metals, such as iron, nickel, and aluminum. These metals would have been knocked out into space during the big bang and later became part of the very first stars in the Milky Way. Over time, other astronomers have discovered that there are many similarities between these ancient Milky Way stars and what we call regular stars today.

Dark matter halo and galaxy formation.

Although astronomers continue to study the Milky Way and the rest of the universe, they also know that there is another theory that explains galaxy formation better than the one described above. It has to do with what is called the dark matter halo. This theory states that all of the gas in the universe is made up of a dark matter halo. Although astronomers have not found conclusive evidence to support this hypothesis, most agree that it does make more sense of the observations than the alternative.


In looking back in time, we see the seeds of a successful galaxy formation. Over time, these seeds germinated and grew into the first stars. The deep field of our own Galaxy may well have had such seeds waiting in the wings. The next time you look at the sky, don’t just take a look at the stars, but think about how they got their beginnings. Perhaps it will help you to realize that understanding cosmology is not as difficult as you might think.


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