There are countless galaxies throughout the universe. So many that new ones are being discovered all the time. Scientists have been studying galaxies for thousands of years, though for many of those years people had no idea what they were looking at. The word “galaxy” comes from the Greek term “galaxies kuklos” or milky circle, used to describe the appearance of what would come to be known as the Milky Way.
Humans have been looking at the Milky Way since time-immemorial, but it wasn’t until the past few hundred years that we began to understand what we were looking at. It wasn’t until 1610 when Galileo and his telescope observed that the white band that appeared in the night sky was indeed made up of distant stars, something which had long been thought, but never proven.
Charles Messier was a French astronomer in the 18th century who was the first to observe and catalog galaxies in the night sky. He saw a number of fuzzy light patches in the sky called “nebulae”. People had noted these patches before, notably the Persian astronomer Al-Sufi who noted them as far back as 964, but Messier was the first person to make an extensive catalog and recognize the spiral shape many of these nebulae had. The patches cataloged by Messier are still known as “Messier Objects“.
Debate raged on for decades as to what these “nebulae” actually were. Scientist had come to believe that our own solar system existed in a concentration of stars but it wasn’t until 1929 when Edward Hubble was able to prove that these distant patches were the same kind of spiral nebulae as our own. Hubble used a massive telescope to not only observe galaxies but determine the kinds of stars within them, their distance to us, and the speed at which they move.
Recently, the Hubble Space Telescope was able to observe a distant “dead galaxy” or a galaxy which is no longer producing stars. The nearby Andromeda galaxy has been dead for several billion years and some scientists have suggested that our own galaxy may be expired. A “dead” galaxy doesn’t mean a non-functioning galaxy, it simply means that no new stars are being created. The galaxy and the objects within it, still moves as live ones do.
“Ghost light” from dead galaxies.
The discovered galaxy, MACS 2129-1, is half the size of the Milk Way but more than twice its density. The stars in MACS 2129-1 are spinning at more than twice the velocity of our stars. More over, the nature of MACS 2129-1 has upended scientists’ previous notions about how galaxies age. Under the current theory, dead galaxies lose their spinning disk shape and take on a more elliptical one. MACS 2129-1 however, has retained its disk shape despite being dead for billions of years causing scientists to rethink some of their theories. Astronomers admit that because there are so many galaxies and that they can be hard to see, our perception of the nature of galaxies is extremely limited.