Ancient people described the Milky Way galaxy as 'a river, milk, and a path', according to legend. The Milky Way galaxy in which we live is just like billions of other galaxies. Most of the stars in the Milky Way are older than the 4.5 billion-year-old sun.
Spiral galaxies comprise about two thirds of the universes galaxies. The Milky Way galaxy is one such spiral galaxy, and it travels 515,000 miles per hour on average. It would take about 230,000,000 years to journey all the way through the Milky Way.
Humans actually can’t see many of the stars in the Milky Way, due to the massive amount of dust and gas covering most of them. In addition to stars, the Milky Way is home to many black holes. All black holes start small, but the big supply of dust and gas in the sky allows them to grow. Humans can’t see black holes, but astronomers can study them by observing their effects on the objects around them.
Additionally, the Milky Way contains two important "minor arms", different sections of the Milky Way. A spur is a smaller version of an arm. One spur called the "Orion arm" contains our solar system. The major arms of the Milky Way are Perseus and Sagittarius. Another entity that makes up this galaxy is dark matter, which take's up a majority of the galaxy's mass.
Because galaxies move around the universe, they are always crashing into one another. However, this doesn't actually affect them. The nearest neighboring galaxy to the Milky Way, the Andromeda galaxy, shows signs that it has crashed into another galaxy in the past. Researchers predict it will also crash into the Milky Way in about four billion years. In fact, the two galaxies are rushing towards each other at a speed of about 70 miles per second. When they crash, they will produce a fresh stream of matter into the universe that will create many new stars. The collision shouldn’t be problematic for life on earth, however, because the sun will already have turned into a red giant at this point in time, thus making Earth uninhabitable.
Every time you look up to the night sky you are observing stars that are 4.5 billion years old. And if you look closely, you might see a swath of light from the Milky Way. Even though the sun will ultimately consume the Earth, it is neat to know that the sky we gaze upon today is the very same one ancient people gazed at many years ago.