How does the universe work?

Despite the turbulent nature of their creation, stars and galaxies follow quite stable life cycles often lasting billions of years. While galaxies vary widely with respect to how they form and disappear, all stars follow similarly structured life cycles from birth to death. Every star in our universe relies on hydrogen to shine, so their life cycle ends when that supply of hydrogen depletes. Smaller stars like the sun will gradually grow dimmer until they stop shining, while larger stars will explode as supernovas at the end of their life cycles.

“Over the course of my lifetime, the night sky isn’t really going to change substantially,” Spenner said. “There might be the occasional supernova or comet, which are surprising but also kind of expected to happen. On a bigger scale, things are definitely still changing; galaxies are constantly evolving, stars are being born and dying.”

One of the most concerning changes discovered by scientists in recent years is the expansion of the universe. Not only has the universe been constantly growing larger since the Big Bang, but studies have shown that the expansion is happening at an accelerating rate, much faster than even the speed of light.

“When scientists detected and observed the CMB radiation, it showed that the universe was expanding,” Kaitlyn said. “When they looked at things that were far away, the wavelengths they saw became longer because they were moving away from us. This effect, redshift, tells us that things farther away appear more red because red is the longest wavelength of light.”

As the universe continues to expand, with it comes no new galaxies or stars. As a result, the ones we have now will gradually drift farther away from us into the outer edges of our universe, leaving us with nothing to see except an empty night sky billions of years into the future.

Currently, scientists calculate the total number of galaxies in our universe to be somewhere between 100 and 200 billion. They arrived at this rough estimation by employing telescopes to take snapshots of the night sky and counting the galaxies contained within that tiny sliver of space. Compiling over 10 years of photos from the Hubble Space Telescope, researchers can study the distance between galaxies in each image and project their observations onto the entire universe.

“If you viewed the contents of the universe with sufficiently poor vision, it would appear roughly the same everywhere and in every direction,” NASA said. “That is, the matter in the universe is homogeneous when averaged over very large scales.”

Out of the billions of galaxies in our universe, each one contains its own unique set of stars and exoplanets, waiting to be discovered. One by one, scientists are just now beginning to uncover the secrets of these planets, all the while in search for the one thing deemed so scientifically probable yet still unattainable: life.